8.104. kernel

Updated kernel packages that fix several security issues and several bugs are now available for Red Hat Enterprise Linux 6.
Red Hat Product Security has rated this update as having Important security impact. Common Vulnerability Scoring System (CVSS) base scores, which give detailed severity ratings, are available for each vulnerability from the CVE links below.
The kernel packages contain the Linux kernel, the core of any Linux operating system.

Security Fixes

CVE-2015-1805, Important
It was found that the Linux kernel's implementation of vectored pipe read and write functionality did not take into account the I/O vectors that were already processed when retrying after a failed atomic access operation, potentially resulting in memory corruption due to an I/O vector array overrun. A local, unprivileged user could use this flaw to crash the system or, potentially, escalate their privileges on the system.
CVE-2015-3331, Important
A buffer overflow flaw was found in the way the Linux kernel's Intel AES-NI instructions optimized version of the RFC4106 GCM mode decryption functionality handled fragmented packets. A remote attacker could use this flaw to crash, or potentially escalate their privileges on, a system over a connection with an active AES-GCM mode IPSec security association.
CVE-2014-9419, Low
An information leak flaw was found in the way the Linux kernel changed certain segment registers and thread-local storage (TLS) during a context switch. A local, unprivileged user could use this flaw to leak the user space TLS base address of an arbitrary process.
CVE-2014-9420, Low
It was found that the Linux kernel's ISO file system implementation did not correctly limit the traversal of Rock Ridge extension Continuation Entries (CE). An attacker with physical access to the system could use this flaw to trigger an infinite loop in the kernel, resulting in a denial of service.
CVE-2014-9585, Low
An information leak flaw was found in the way the Linux kernel's Virtual Dynamic Shared Object (vDSO) implementation performed address randomization. A local, unprivileged user could use this flaw to leak kernel memory addresses to user-space.
Red Hat would like to thank Carl Henrik Lunde for reporting CVE-2014-9420. The security impact of the CVE-2015-1805 issue was discovered by Red Hat.

Bug Fixes

BZ#1201674
When repeating a Coordinated Universal Time (UTC) value during a leap second (when the UTC time should be 23:59:60), the International Atomic Time (TAI) timescale previously stopped as the kernel NTP code incremented the TAI offset one second later than expected. A patch has been provided, which fixes the bug by incrementing the offset during the leap second itself. Now, the correct TAI is set during the leap second.
BZ#1204626
Due to a race condition, deleting a cgroup while pages belonging to that group were being swapped in could trigger a kernel crash. This update fixes the race condition, and deleting a cgroup is now safe even under heavy swapping.
BZ#1207815
Previously, the open() system call in some cases failed with an EBUSY error if the opened file was also being renamed at the same time. With this update, the kernel automatically retries open() when this failure occurs, and if the retry is not successful either, open() now fails with an ESTALE error.
BZ#1208620
Prior to this update, cgroup blocked new threads from joining the target thread group during cgroup migration, which led to a race condition against exec() and exit() functions, and a consequent kernel panic. This bug has been fixed by extending thread group locking such that it covers all operations which can alter the thread group - fork(), exit(), and exec(), and cgroup migration no longer causes the kernel to panic.
BZ#1211940
The hrtimer_start() function previously attempted to reinsert a timer which was already defined. As a consequence, the timer node pointed to itself and the rb_insert_color() function entered an infinite loop. This update prevents the hrtimer_enqueue_reprogram() function from racing and makes sure the timer state in remove_hrtimer() is preserved, thus fixing the bug.
BZ#1144442
Previously, the bridge device did not propagate VLAN information to its ports and Generic Receive Offload (GRO) information to the connected devices. This resulted in lower receive performance of VLANs over bridge devices because GRO was not enabled. An attempt to resolve this problem was made with BZ#858198 by introducing a patch that allows VLANs to be registered with the participating bridge ports and adds GRO to the bridge device feature set. However, this attempt introduced a number of regressions, which broke the vast majority of stacked setups involving bridge devices and VLANs. This update reverts the patch provided by BZ#858198 and removes support for this capability.
BZ#1199900
Previously, the kernel initialized FPU state for the signal handler too early, right after the current state was saved for the sigreturn() function. As a consequence, a task could lose its floating-point unit (FPU) context if the signal delivery failed. The fix ensures that the drop_init_fpu() fuction is only called when the signal is delivered successfully, and FPU context is no longer lost in the described situation.
BZ#1203366
On mounting a Common Internet File System (CIFS) share using kerberos authentication, the CIFS module uses the request_key mechanism to obtain the user's krb5 credentials. Once the key has been used and is no longer needed, CIFS revoked it. This caused key revoked errors to be returned when attempting to refetch the key. To fix this bug, the key_invalidate() call has been backported from the upstream code to discard the key. This call renders the discarded key invisible to further searches and wakes up the garbage collector immediately to remove the key from the keyrings and to destroy it. As a result, discarded keys are immediately cleared and are no longer returned on key searches.
BZ#1203544
Previously, the fc_remote_port_del() call preceded the calls to re-establish the session with the Fibre Channel (FC) transport with the fc_remote_port_add() and fc_remote_port_rolechg() functiones. With this update, the fc_remote_port_del() call has been removed before re-establishing the connection, which prevents the race condition from occurring.
BZ#1210593
Due to a race condition in the build_id_cache__add_s() function, system files could be truncated. This update fixes the race condition, and system files are no longer truncated in the aforementioned situation.
BZ#1212057
Prior to this update, the "--queue-balance" option did not distribute traffic over multiple queues as the option ignored a request to balance among the given range and only used the first queue number given. As a consequence, the kernel traffic was limited to one queue. The underlying source code has been patched, and the kernel traffic is now balanced within the given range.

Enhancements

BZ#1173501, BZ#1173562
This update introduces a set of patches with a new VLAN model to conform to upstream standards. In addition, this set of patches fixes other issues such as transmision of Internet Control Message Protocol (ICMP) fragments.
Users of kernel are advised to upgrade to these updated packages, which contain backported patches to correct these issues. The system must be rebooted for this update to take effect.
Updated kernel packages that fix multiple security issues and several bugs are now available for Red Hat Enterprise Linux 6.
Red Hat Product Security has rated this update as having Important security impact. Common Vulnerability Scoring System (CVSS) base scores, which give detailed severity ratings, are available for each vulnerability from the CVE links below.
The kernel packages contain the Linux kernel, the core of any Linux operating system.

Security Fixes

CVE-2014-3215, Important
A flaw was found in the way seunshare, a utility for running executables under a different security context, used the capng_lock functionality of the libcap-ng library. The subsequent invocation of suid root binaries that relied on the fact that the setuid() system call, among others, also sets the saved set-user-ID when dropping the binaries' process privileges, could allow a local, unprivileged user to potentially escalate their privileges on the system. Note: the fix for this issue is the kernel part of the overall fix, and introduces the PR_SET_NO_NEW_PRIVS functionality and the related SELinux exec transitions support.
CVE-2015-1421, Important
A use-after-free flaw was found in the way the Linux kernel's SCTP implementation handled authentication key reference counting during INIT collisions. A remote attacker could use this flaw to crash the system or, potentially, escalate their privileges on the system.
CVE-2014-3690, Moderate
It was found that the Linux kernel's KVM implementation did not ensure that the host CR4 control register value remained unchanged across VM entries on the same virtual CPU. A local, unprivileged user could use this flaw to cause a denial of service on the system.
CVE-2014-7825, Moderate
An out-of-bounds memory access flaw was found in the syscall tracing functionality of the Linux kernel's perf subsystem. A local, unprivileged user could use this flaw to crash the system.
CVE-2014-7826, Moderate
An out-of-bounds memory access flaw was found in the syscall tracing functionality of the Linux kernel's ftrace subsystem. On a system with ftrace syscall tracing enabled, a local, unprivileged user could use this flaw to crash the system, or escalate their privileges.
CVE-2014-8171, Moderate
It was found that the Linux kernel memory resource controller's (memcg) handling of OOM (out of memory) conditions could lead to deadlocks. An attacker able to continuously spawn new processes within a single memory-constrained cgroup during an OOM event could use this flaw to lock up the system.
CVE-2014-9529, Moderate
A race condition flaw was found in the way the Linux kernel keys management subsystem performed key garbage collection. A local attacker could attempt accessing a key while it was being garbage collected, which would cause the system to crash.
CVE-2014-8884, Low
A stack-based buffer overflow flaw was found in the TechnoTrend/Hauppauge DEC USB device driver. A local user with write access to the corresponding device could use this flaw to crash the kernel or, potentially, elevate their privileges on the system.
CVE-2014-9584, Low
An information leak flaw was found in the way the Linux kernel's ISO9660 file system implementation accessed data on an ISO9660 image with RockRidge Extension Reference (ER) records. An attacker with physical access to the system could use this flaw to disclose up to 255 bytes of kernel memory.
Red Hat would like to thank Andy Lutomirski for reporting CVE-2014-3215 and CVE-2014-3690, Robert Święcki for reporting CVE-2014-7825 and CVE-2014-7826, and Carl Henrik Lunde for reporting CVE-2014-9584. The CVE-2015-1421 issue was discovered by Sun Baoliang of Red Hat.

Bug Fixes

BZ#1195747
Due to a regression, when large reads which partially extended beyond the end of the underlying device were done, the raw driver returned the EIO error code instead of returning a short read covering the valid part of the device. The underlying source code has been patched, and the raw driver now returns a short read for the remainder of the device.
BZ#1187639
Previously, a NULL pointer check that is needed to prevent an oops in the nfs_async_inode_return_delegation() function was removed. As a consequence, a NFS4 client could terminate unexpectedly. The missing NULL pointer check has been added back, and NFS4 client no longer crashes in this situation.
BZ#1187666
A failure to leave a multicast group which had previously been joined prevented the attempt to unregister from the "sa" service. Multiple locking issues in the IPoIB multicast join and leave processing have been fixed so that leaving a group that has completed its join process is successful. As a result, attempts to unregister from the "sa" service no longer lock up due to leaked resources.
BZ#1187664
Due to unbalanced multicast join and leave processing, the attempt to leave a multicast group that had not previously completed a join became unresponsive. This update resolves multiple locking issues in the IPoIB multicast code that allowed multicast groups to be left before the joining was entirely completed. Now, multicast join and leave failures or lockups no longer occur in the described situation.
BZ#1188339
The kernel source code contained two definitions of the cpu_logical_map() function, which maps logical CPU numbers to physical CPU addresses. When translating the logical CPU number to the corresponding physical CPU number, the kernel used the second definition of cpu_logical_map(), which always used a one-to-one mapping of logical to physical CPU addresses. This mapping was, however, wrong after a reboot, especially if the target CPU was in the "stopped" state. Consequently, the system became unresponsive or showed unexpected latencies. With this update, the second definition of cpu_logical_map() has been removed. As a result, the kernel now correctly translates the CPU number to its physical address, and no unexpected latencies occur in this scenario.
BZ#1188838
Previously, the kernel could under certain circumstances provide the tcp_collapse() function with a socket buffer (SKB) whose "headroom" was equal to the value of the PAGE_SIZE variable. Consequently, the copy value was zero in the loop, which could never exit because it was not making forward progress. To fix this problem, the loop has been rewritten to avoid the incorrect calculation. Instead, the loop copies either the value of the PAGE_SIZE variable or the size of the buffer, whichever is bigger. As a result, the tcp_collapse() function is no longer apt to get stuck in the loop, because the copy is always non-zero as long as long as the "end" differs from the "start".
BZ#1188941
Prior to this update, when using the fibre channel driver, a race condition occurred in the rport scsi_remove_target() function. As a consequence, the kernel terminated unexpectedly when dereferencing an invalid address. To fix this bug, the changes to the reference counting infrastructure have been reverted, and the system no longer crashes.
BZ#1191916
On older systems without the QCI instruction, all possible domains are probed via TAPQ instruction. Prior to this update, a specification exception could occur when this instruction was called for probing values greater than 16; for example, during the execution of the "insmod" command or the reset of the AP bus on machines without the QCI instruction (z10, z196, z114). zEC12 and newer systems were not affected. Consequently, loading the z90crypt kernel module caused a panic. Now, the domain checking function has been corrected to limit the allowed range if no QCI information is available. As a result, users are able to successfully load and perform cryptographic functions with the z90crypt device driver.
BZ#1192055
Previously, KVM took a page fault with interrupts disabled. Consequently, the page fault handler tried to take a lock, but KSM sent an IPI while taking the same lock. Then KSM waited for the IPI to be processed, but KVM would not process it until it took the lock. KSM and KVM would eventually encounter a deadlock, each waiting for the other. With this update, the kernel avoids operations that can page fault while interrupts are disabled. As a result, KVM and KSM are no longer prone to a deadlock in the aforementioned scenario.
BZ#1192105
The USB core uses the "hcpriv" member of the USB request block to determine whether a USB Request Block (URB) is active, but the ehci-hcd driver was not setting this correctly when it queued isochronous URBs. This in combination with a defect in the snd-usb-audio driver could cause URBs to be reused without waiting for them to complete. Consequently, list corruption followed by system freeze or a kernel crash occurred. To fix this problem, the ehci-hcd driver code has been updated to properly set the "hcpriv" variable for isochronous URBs, and the snd-usb-audio driver has been updated to synchronize pending stop operations on an endpoint before continuing with preparing the PCM stream. As a result, list corruption followed by system freeze or a crash no longer occurs.
BZ#1193639
Previously, the Hewlett Packard Smart Array (HPSA) driver in conjunction with an older version of the HPSA firmware and the hp-snmp-agent monitoring software used the "system work queue" shared resource for an extensively long time. Consequently, random other tasks were blocked until the HPSA driver released the work queue, and messages such as the following were logged:
INFO: task sshd:6425 blocked for more than 120 seconds.
INFO: task ptymonitor:22510 blocked for more than 120 seconds.
With this update, the HPSA driver creates its own local work queue, which fixes this problem.
BZ#1198329
Prior to this update, the GFS2 file system's "Splice Read" operation, which is used for functions such as sendfile(), was not properly allocating a required multi-block reservation structure in memory. As a consequence, when the GFS2 block allocator was called to assign blocks of data, it tried to dereference the structure, which resulted in a kernel panic. Now, GFS2's "Splice read" operation has been changed so that it properly allocates the necessary reservation structure in memory prior to calling the block allocator. As a result, sendfile() now works properly for GFS2.
Users of kernel are advised to upgrade to these updated packages, which contain backported patches to correct these issues. The system must be rebooted for this update to take effect.
Updated kernel packages that fix two security issues and several bugs are now available for Red Hat Enterprise Linux 6.
Red Hat Product Security has rated this update as having Important security impact. Common Vulnerability Scoring System (CVSS) base scores, which give detailed severity ratings, are available for each vulnerability from the CVE links below.
The kernel packages contain the Linux kernel, the core of any Linux operating system.

Security Fixes

CVE-2014-7841, Important
A flaw was found in the way the Linux kernel's SCTP implementation validated INIT chunks when performing Address Configuration Change (ASCONF). A remote attacker could use this flaw to crash the system by sending a specially crafted SCTP packet to trigger a NULL pointer dereference on the system.
CVE-2014-4656, Moderate
An integer overflow flaw was found in the way the Linux kernel's Advanced Linux Sound Architecture (ALSA) implementation handled user controls. A local, privileged user could use this flaw to crash the system.
The CVE-2014-7841 issue was discovered by Liu Wei of Red Hat.

Bug Fixes

BZ#1161420
LVM2 thin provisioning is sensitive to I/Os within a full RAID stripe is issued to the controller's write-back cache in close proximity. This update improves LVM2 thin provisioning to work more efficiently on RAID devices.
BZ#1161421
Previously, under a heavy I/O load, a timeout of an unresponsive task could occur while using LVM2 thin provisioning. With this update, various infrastructure used by LVM2 thin provisioning have been improved to be more efficient and correct. This includes the use of more efficient data structures, throttling worker threads to prevent an application from sending more I/O than can be handled, and pre-fetching metadata. This update also fixes the eviction logic used by the metadata I/O buffering layer, which ensures that metadata blocks are not evicted prematurely.
BZ#1162072
Due to a malfunction in the USB controller driver, some data stream metadata was dropped. As a consequence, the integrated camera to failed to record with the following error message:
libv4l2: error turning on stream: No space left on device
This update fixes the data stream metadata handling, and the integrated camera works as expected.
BZ#1165986
Before this update, a race condition occurred in the spin-lock logic on the PowerPC platform. Consequently, workloads caused heavy use of Inter-Process Communication (IPC), and the kernel could terminate unexpectedly. This update adds proper synchronization to the PowerPC spin-lock framework. As a result, the kernel no longer crashes under heavy use of IPC.
BZ#1163214
Due to an overlooked piece of code that initializes the pre-operation change attribute, certain workloads could generate unnecessary cache invalidations and additional NFS read operations. This update fixes the initialization of the pre_change_attr field, which prevents unnecessarily cached data invalidation.
BZ#1165001
Previously, under certain error conditions gfs2_converter introduced incorrect values for the on-disk inode's di_goal_meta field. As a consequence, gfs2_converter returned the EBADSLT error on such inodes and did not allow creation of the new files in directories or new blocks in regular files. The fix allows gfs2_converter to set a sensible goal value if a corrupt one is encountered and proceed with normal operations. With this update, gfs2_converter implicitly fixes any corrupt goal values, and thus no longer disrupts normal operations.
BZ#1165002
Previously, under certain error conditions using the semaphore utility caused the kernel to become unresponsive. With update a patch has been applied to fix this bug. As a result, the the kernel hangs no longer occur while using semaphore.
BZ#1165985
Before this update, due to a coding error in the e100 Ethernet driver update, physical layers (PHYs) did not initialize correctly. This could cause RX errors and decreased throughput, especially when using long UTP cabling. This update fixes the coding error, and as a result, the aforementioned scenario no longer occurs on the e100 Ethernet device.
BZ#1168129
Before this update, a flaw in the duplicate reply cache in the NFS daemon allowed entries to be freed while they were still used. Consequently, a heavily loaded NFS daemon could terminate unexpectedly if an RPC call took a long time to process. The cache has been fixed to protect such entries from freeing, and the server now functions normally in the aforementioned scenario.
BZ#1168504
Previously, external journal blocks were handled as blocks causing an increase of processor usage. Consequently, on the ext4 file systems configured with an external journal device, the df command could show negative values due to the subtraction of such journal blocks amount from the used blocks amount. With this update, the external journal blocks are handled properly, and therefore df no longer returns negative values.
BZ#1169433
Before this update, raising the SIGBUS signal did not include a siginfo structure describing the cause of the SIGBUS exception. As a consequence, applications that use huge pages using the libhugetlbfs library failed. The PACKAGE_NAME has been updated to raise SIGBUS with a siginfo structure, to deliver BUS_ADRERR as si_code, and to deliver the address of the fault in the si_addr field. As a result, applications that use huge pages no longer fail in the aforementioned scenario.
BZ#1172022
Previously, accessing a FUSE-based file system from kernel space could cause the kernel to become unresponsive during an inode look-up operation. To fix this bug, existing flags are verified before dereference occurs in the FUSE look-up handler. As a result, accessing a FUSE-based file system from kernel space works as expected.
BZ#1172024
Previously, hot plugging of a USB EHCI controller could cause the kernel to become unresponsive. This update fixes the handling of a race condition in the EHCI error path during the hot-plugging event, and the kernel no longer hangs.
BZ#1172025
Previously, the system functions semop() and semtimedop() did not update the time of the semaphore update located in the structure sem_otime, which was inconsistent with the function description in the man pages. With this update, a patch has been applied to fix this bug. As a result, semop() and semtimedop() now properly update the sem_otime structure.
BZ#1172027
Before this update, when forwarding a packet, the iptables target TCPOPTSTRIP used the tcp_hdr() function to locate the option space. Consequently, TCPOPTSTRIP located the incorrect place in the packet, and therefore did not match options for stripping. With this update, TCPOPTSTRIP now uses the TCP header itself to locate the option space. As a result, the options are now properly stripped.
BZ#1172764
Prior to this update, the ipset utility computed incorrect values of timeouts from an old IP set, and these values were then supplied to a IP new set. As a consequence, a resize on a IP set with a timeouts option enabled could supply corrupted data from an old IP set. This bug has been fixed by properly reading timeout values from an old set before supplying them to a new set.
BZ#1172029
Previously, under certain conditions, a race condition between the semaphore creation code and the semop() function caused the kernel to become unresponsive. With this update, a patch has been applied, and the kernel hangs no longer occur.
BZ#1172030
Prior to this update, a NULL pointer dereference could occur when then usb_wwan device driver was performing a disconnect operation. The usb_wwan disconnect procedure has been replaced with the port_remove procedure and, as a result, the kernel no longer hangs when removing a WWAN USB device.
BZ#1175509
The usage of PCLMULQDQ instruction required the invocation of the kernel_fpu_begin() and kernel_fpu_end() functions. Consequently, the usage of the PCLMULQDQ instruction for the CRC32C checksum calculation incurred some increase of processor usage. With this update, a new function has been added in order to calculate the CRC32C checksum using the PCLMULQDQ instruction on processors that support this feature, which provides speedup over using the CRC32 instruction only.
Users of kernel are advised to upgrade to these updated packages, which contain backported patches to correct these issues. The system must be rebooted for this update to take effect.
Updated kernel packages that fix multiple security issues, address several hundred bugs, and add numerous enhancements are now available as part of the ongoing support and maintenance of Red Hat Enterprise Linux version 6. This is the sixth regular update.
Red Hat Product Security has rated this update as having Important security impact. Common Vulnerability Scoring System (CVSS) base scores, which give detailed severity ratings, are available for each vulnerability from the CVE links below.
The kernel packages contain the Linux kernel, the core of any Linux operating system.

Security Fixes

CVE-2014-5077, Important
A NULL pointer dereference flaw was found in the way the Linux kernel's Stream Control Transmission Protocol (SCTP) implementation handled simultaneous connections between the same hosts. A remote attacker could use this flaw to crash the system.
CVE-2013-2596, Important
An integer overflow flaw was found in the way the Linux kernel's Frame Buffer device implementation mapped kernel memory to user space via the mmap syscall. A local user able to access a frame buffer device file (/dev/fb*) could possibly use this flaw to escalate their privileges on the system.
CVE-2013-4483, Moderate
A flaw was found in the way the ipc_rcu_putref() function in the Linux kernel's IPC implementation handled reference counter decrementing. A local, unprivileged user could use this flaw to trigger an Out of Memory (OOM) condition and, potentially, crash the system.
CVE-2014-0181, Moderate
It was found that the permission checks performed by the Linux kernel when a netlink message was received were not sufficient. A local, unprivileged user could potentially bypass these restrictions by passing a netlink socket as stdout or stderr to a more privileged process and altering the output of this process.
CVE-2014-3122, Moderate
It was found that the try_to_unmap_cluster() function in the Linux kernel's Memory Managment subsystem did not properly handle page locking in certain cases, which could potentially trigger the BUG_ON() macro in the mlock_vma_page() function. A local, unprivileged user could use this flaw to crash the system.
CVE-2014-3601, Moderate
A flaw was found in the way the Linux kernel's kvm_iommu_map_pages() function handled IOMMU mapping failures. A privileged user in a guest with an assigned host device could use this flaw to crash the host.
CVE-2014-4653, CVE-2014-4654, CVE-2014-4655, Moderate
Multiple use-after-free flaws were found in the way the Linux kernel's Advanced Linux Sound Architecture (ALSA) implementation handled user controls. A local, privileged user could use either of these flaws to crash the system.
CVE-2014-5045, Moderate
A flaw was found in the way the Linux kernel's VFS subsystem handled reference counting when performing unmount operations on symbolic links. A local, unprivileged user could use this flaw to exhaust all available memory on the system or, potentially, trigger a use-after-free error, resulting in a system crash or privilege escalation.
CVE-2014-4608, Low
An integer overflow flaw was found in the way the lzo1x_decompress_safe() function of the Linux kernel's LZO implementation processed Literal Runs. A local attacker could, in extremely rare cases, use this flaw to crash the system or, potentially, escalate their privileges on the system.
Red Hat would like to thank Vladimir Davydov of Parallels for reporting CVE-2013-4483, Jack Morgenstein of Mellanox for reporting CVE-2014-3601, Vasily Averin of Parallels for reporting CVE-2014-5045, and Don A. Bailey from Lab Mouse Security for reporting CVE-2014-4608. The security impact of the CVE-2014-3601 issue was discovered by Michael Tsirkin of Red Hat.

Bug Fixes

BZ#1065187
A bug in the megaraid_sas driver could cause the driver to read the hardware status values incorrectly. As a consequence, the RAID card was disabled during the system boot and the system could fail to boot. With this update, the megaraid_sas driver has been corrected so that the RAID card is now enabled on system boot as expected.
BZ#1063699
Due to a ndlp list corruption bug in the lpfc driver, systems with Emulex LPe16002B-M6 PCIe 2-port 16Gb Fibre Channel Adapters could trigger a kernel panic during I/O operations. A series of patches has been backported to address this problem so the kernel no longer panics during I/O operations on the aforementioned systems.
BZ#704190
Previously, when using a bridge interface configured on top of a bonding interface, the bonding driver was not aware of IP addresses assigned to the bridge. Consequently, with ARP monitoring enabled, the ARP monitor could not target the IP address of the bridge when probing the same subnet. The bridge was thus always reported as being down and could not be reached. With this update, the bonding driver has been made aware of IP addresses assigned to a bridge configured on top of a bonding interface, and the ARP monitor can now probe the bridge as expected. Note that the problem still occurs if the arp_validate option is used. Therefore, do not use this option in this case until this issue is fully resolved.
BZ#1063478, BZ#1065398, BZ#1065404, BZ#1043540, BZ#1096328
Several concurrency problems, that could result in data corruption, were found in the implementation of CTR and CBC modes of operation for AES, DES, and DES3 algorithms on IBM S/390 systems. Specifically, a working page was not protected against concurrency invocation in CTR mode. The fallback solution for not getting a working page in CTR mode did not handle iv values correctly. The CBC mode used did not properly save and restore the key and iv values in some concurrency situations. All these problems have been addressed in the code and the concurrent use of the aforementioned algorithms no longer cause data corruption.
BZ#1061873
A previous change in the Advanced Programmable Interrupt Controller (APIC) code caused a regression on certain Intel CPUs using a Multiprocessor (MP) table. An attempt to read from the local APIC (LAPIC) could be performed before the LAPIC was mapped, resulting in a kernel crash during a system boot. A patch has been applied to fix this problem by mapping the LAPIC as soon as possible when parsing the MP table.
BZ#1060886
A miscalculation in the "radix_tree" swap encoding corrupted swap area indexes bigger than 8 by truncating lower bits of swap entries. Consequently, systems with more than 8 swap areas could trigger a bogus OOM scenario when swapping out to such a swap area. This update fixes this problem by reducing a return value of the SWP_TYPE_SHIFT() function and removing a broken function call from the read_swap_header() function.
BZ#1060381
Previously some device mapper kernel modules, such as dm-thin, dm-space-map-metadata, and dm-bufio, contained various bugs that had adverse effects on their proper functioning. This update backports several upstream patches that resolve these problems, including a fix for the metadata resizing feature of device mapper thin provisioning (thinp) and fixes for read-only mode for dm-thin and dm-bufio. As a result, the aforementioned kernel modules now contain the latest upstream changes and work as expected.
BZ#1059808
When an attempt to create a file on the GFS2 file system failed due to a file system quota violation, the relevant VFS inode was not completely uninitialized. This could result in a list corruption error. This update resolves this problem by correctly uninitializing the VFS inode in this situation.
BZ#1059777
In Red Hat Enterprise Linux 6.5, the TCP Segmentation Offload (TSO) feature is automatically disabled if the corresponding network device does not report any CSUM flag in the list of its features. Previously, VLAN devices that were configured over bonding devices did not propagate its NETIF_F_NO_CSUM flag as expected, and their feature lists thus did not contain any CSUM flags. As a consequence, the TSO feature was disabled for these VLAN devices, which led to poor bandwidth performance. With this update, the bonding driver propagates the aforementioned flag correctly so that network traffic now flows through VLAN devices over bonding without any performance problems.
BZ#1059586
Due to a bug in the mlx4_en module, a data structure related to time stamping could be accessed before being initialized. As a consequence, loading mlx4_en could result in a kernel crash. This problem has been fixed by moving the initiation of the time stamp mechanism to the correct place in the code.
BZ#1059402
Due to a previous change that was refactoring the Generic Routing Encapsulation (GRE) tunneling code, the ip_gre module did not work properly. As a consequence, GRE interfaces dropped every packet that had the Explicit Congestion Notification (ECN) bit set and did not have the ECN-Capable Transport (ECT) bit set. This update reintroduces the ipgre_ecn_decapsulate() function that is now used instead of the IP_ECN_decapsulate() function that was not properly implemented. The ip_gre module now works correctly and GRE devices process all packets as expected.
BZ#1059334
When removing an inode from a name space on an XFS file system, the file system could enter a deadlock situation and become unresponsive. This happened because the removal operation incorrectly used the AGF and AGI locks in the opposite order than was required by the ordering constraint, which led to a possible deadlock between the file removal and inode allocation and freeing operations. With this update, the inode's reference count is dropped before removing the inode entry with the first transaction of the removal operation. This ensures that the AGI and AGF locks are locked in the correct order, preventing any further deadlocks in this scenario.
BZ#1059325
Previously, the for_each_isci_host() macro was incorrectly defined so it accessed an out-of-range element for a 2-element array. This macro was also wrongly optimized by GCC 4.8 so that it was executed too many times on platforms with two SCU controllers. As a consequence, the system triggered a kernel panic when entering the S3 state, or a kernel oops when removing the isci module. This update corrects the aforementioned macro and the described problems no longer occur.
BZ#1067722
A previous change enabled receive acceleration for VLAN interfaces configured on a bridge interface. However, this change allowed VLAN-tagged packets to bypass the bridge and be delivered directly to the VLAN interfaces. This update ensures that the traffic is correctly processed by a bridge before it is passed to any VLAN interfaces configured on that bridge.
BZ#844450
The Completely Fair Scheduler (CFS) did not verify whether the CFS period timer is running while throttling tasks on the CFS run queue. Therefore under certain circumstances, the CFS run queue became stuck because the CFS period timer was inactive and could not be restarted. To fix this problem, the CFS now restarts the CFS period timer inside the throttling function if it is inactive.
BZ#1069028
Due to a bug in the ixgbevf driver, the stripped VLAN information from incoming packets on the ixgbevf interface could be lost, and such packets thus did not reach a related VLAN interface. This problem has been fixed by adding the packet's VLAN information to the Socket Buffer (skb) before passing it to the network stack. As a result, the ixgbevf driver now passes the VLAN-tagged packets to the appropriate VLAN interface.
BZ#1069737
Previous patches to the CIFS code introduced a regression that prevented users from mounting a CIFS share using the NetBIOS over TCP service on the port 139. This problem has been fixed by masking off the top byte in the get_rfc1002_length() function.
BZ#880024
Previously, the locking of a semtimedop semaphore operation was not fine enough with remote non-uniform memory architecture (NUMA) node accesses. As a consequence, spinlock contention occurred, which caused delays in the semop() system call and high load on the server when running numerous parallel processes accessing the same semaphore. This update improves scalability and performance of workloads with a lot of semaphore operations, especially on larger NUMA systems. This improvement has been achieved by turning the global lock for each semaphore array into a per-semaphore lock for many semaphore operations, which allows multiple simultaneous semop() operations. As a result, performance degradation no longer occurs.
BZ#886723
A rare race between the file system unmount code and the file system notification code could lead to a kernel panic. With this update, a series of patches has been applied to the kernel to prevent this problem.
BZ#885517
A bug in the bio layer could prevent user space programs from writing data to disk when the system run under heavy RAM memory fragmentation conditions. This problem has been fixed by modifying a respective function in the bio layer to refuse to add a new memory page only if the page would start a new memory segment and the maximum number of memory segments has already been reached.
BZ#1070856
A bug in the qla2xxx driver caused the kernel to crash. This update resolves this problem by fixing an incorrect condition in the "for" statement in the qla2x00_alloc_iocbs() function.
BZ#1072373
A previous change that introduced global clock updates caused guest machines to boot slowly when the host Time Stamp Counter (TSC) was marked as unstable. The slow down increased with the number of vCPUs allocated. To resolve this problem, a patch has been applied to limit the rate of the global clock updates.
BZ#1055644
A previously backported patch to the XFS code added an unconditional call to the xlog_cil_empty() function. If the XFS file system was mounted with the unsupported nodelaylog option, that call resulted in access to an uninitialized spin lock and a consequent kernel panic. To avoid this problem, the nodelaylog option has been disabled; the option is still accepted but has no longer any effect. (The nodelaylog mount option was originally intended only as a testing option upstream, and has since been removed.)
BZ#1073129
Due to a bug in the hrtimers subsystem, the clock_was_set() function called an inter-processor interrupt (IPI) from soft IRQ context and waited for its completion, which could result in a deadlock situation. A patch has been applied to fix this problem by moving the clock_was_set() function call to the working context. Also during the resume process, the hrtimers_resume() function reprogrammed kernel timers only for the current CPU because it assumed that all other CPUs are offline. However, this assumption was incorrect in certain scenarios, such as when resuming a Xen guest with some non-boot CPUs being only stopped with IRQs disabled. As a consequence, kernel timers were not corrected on other than the boot CPU even though those CPUs were online. To resolve this problem, hrtimers_resume() has been modified to trigger an early soft IRQ to correctly reprogram kernel timers on all CPUs that are online.
BZ#1073218
A bug in the vmxnet3 driver allowed potential race conditions to be triggered when the driver was used with the netconsole module. The race conditions allowed the driver's internal NAPI poll routine to run concurrently with the netpoll controller routine, which resulted in data corruption and a subsequent kernel panic. To fix this problem, the vmxnet3 driver has been modified to call the appropriate interrupt handler to schedule NAPI poll requests properly.
BZ#1075713
The Red Hat GFS2 file system previously limited a number of ACL entries per inode to 25. However, this number was insufficient in some cases, causing the setfacl command to fail. This update increases this limit to maximum of 300 ACL entries for the 4 KB block size. If the block size is smaller, this value is adjusted accordingly.
BZ#1053547
The SCTP sctp_connectx() ABI did not work properly for 64-bit kernels compiled with 32-bit emulation. As a consequence, applications utilizing the sctp_connectx() function did not run in this case. To fix this problem, a new ABI has been implemented; the COMPAT ABI enables to copy and transform user data from a COMPAT-specific structure to a SCTP-specific structure. Applications that require sctp_connectx() now work without any problems on a system with a 64-bit kernel compiled with 32-bit emulation.
BZ#1075805
Previously, if a hrtimer interrupt was delayed, all future pending hrtimer events that were queued on the same processor were also delayed until the initial hrtimer event was handled. This could cause all hrtimer processing to stop for a significant period of time. To prevent this problem, the kernel has been modified to handle all expired hrtimer events when handling the initially delayed hrtimer event.
BZ#915862
A previous change in the NFSv4 code resulted in breaking the sync NFSv4 mount option. A patch has been applied that restores functionality of the sync mount option.
BZ#1045150
The code responsible for creating and binding of packet sockets was not optimized and therefore applications that utilized the socket() and bind() system calls did not perform as expected. A patch has been applied to the packet socket code so that latency for socket creating and binding is now significantly lower in certain cases.
BZ#919756
A race condition between completion and timeout handling in the block device code could sometimes trigger a BUG_ON() assertion, resulting in a kernel panic. This update resolves this problem by relocating a relevant function call and the BUG_ON() assertion in the code.
BZ#1044117
The context of the user's process could not be previously saved on PowerPC platforms if the VSX Machine State Register (MSR) bit was set but the user did not provide enough space to save the VSX state. This update allows to clear the VSX MSR bit in such a situation, indicating that there is no valid VSX state in the user context.
BZ#1043733
The kernel task scheduler could trigger a race condition while migrating tasks over CPU cgroups. The race could result in accessing a task that pointed to an incorrect parent task group, causing the system to behave unpredictably, for example to appear being unresponsive. This problem has been resolved by ensuring that the correct task group information is properly stored during the task's migration.
BZ#1043353
Previously, when hot adding memory to the system, the memory management subsystem always performed unconditional page-block scans for all memory sections being set online. The total duration of the hot add operation depends on both, the size of memory that the system already has and the size of memory that is being added. Therefore, the hot add operation took an excessive amount of time to complete if a large amount of memory was added or if the target node already had a considerable amount of memory. This update optimizes the code so that page-block scans are performed only when necessary, which greatly reduces the duration of the hot add operation.
BZ#1043051
Due to a bug in the SELinux socket receive hook, network traffic was not dropped upon receiving a peer:recv access control denial on some configurations. A broken labeled networking check in the SELinux socket receive hook has been corrected, and network traffic is now properly dropped in the described case.
BZ#1042731
Recent changes in the d_splice_alias() function introduced a bug that allowed d_splice_alias() to return a dentry from a different directory than was the directory being looked up. As a consequence in cluster environment, a kernel panic could be triggered when a directory was being removed while a concurrent cross-directory operation was performed on this directory on another cluster node. This update avoids the kernel panic in this situation by correcting the search logic in the d_splice_alias() function so that the function can no longer return a dentry from an incorrect directory.
BZ#1040385
When utilizing SCTP over the bonding device in Red Hat Enterprise Linux 6.5 and later, SCTP assumed offload capabilities on virtual devices where it was not guaranteed that underlying physical devices are equipped with these capabilities. As a consequence, checksums of the outgoing packets became corrupted and a network connection could not be properly established. A patch has been applied to ensure that checksums of the packages to the devices without SCTP checksum capabilities are properly calculated in software fallback. SCTP connections over the bonding devices can now be established as expected in Red Hat Enterprise Linux 6.5 and later.
BZ#1039723
A previous change in the TCP code that extended the "proto" struct with a new function, release_cb(), broke integrity of the kernel Application Binary Interface (kABI). If the core stack called a newly introduced pointer to this function for a module that was compiled against older kernel headers, the call resulted in out-of-bounds access and a subsequent kernel panic. To avoid this problem, the core stack has been modified to recognize a newly introduced slab flag, RHEL_EXTENDED_PROTO. This allows the core stack to safely access the release_cb pointer only for modules that support it.
BZ#1039534
A previous change removed the ZONE_RECLAIM_LOCKED flag from Linux memory management code in order to fix a NUMA node allocation problem in the memory zone reclaim logic. However, the flag removal allowed concurrent page reclaiming within one memory zone, which, under heavy system load, resulted in unwanted spin lock contention and subsequent performance problems (systems became slow or unresponsive). This update resolves this problem by preventing reclaim threads from scanning a memory zone if the zone does not satisfy scanning requirements. Systems under heavy load no longer suffer from CPU overloading but sustain their expected performance.
BZ#1082127
NFSv4 incorrectly handled a situation when an NFS client received an NFS4ERR_ADMIN_REVOKED error after sending a CLOSE operation. As a consequence, the client kept sending the same CLOSE operation indefinitely although it was receiving NFS4ERR_ADMIN_REVOKED errors. A patch has been applied to the NFSv4 code to ensure that the NFS client sends the particular CLOSE operation only once in this situation.
BZ#1037467
Due to recent changes in the Linux memory management, the kernel did not properly handle per-CPU LRU page vectors when hot unplugging CPUs. As a consequence, the page vector of the relevant offline CPU kept memory pages for memory accounting. This prevented the libvirtd daemon from removing the relevant memory cgroup directory upon system shutdown, rendering libvirtd unresponsive. To resolve this problem, the Linux memory management now properly flushes memory pages of offline CPUs from the relevant page vectors.
BZ#1037465
An incorrectly placed function call in the cgroup code prevented the notify_on_release functionality from working properly. This functionality is used to remove empty cgroup directories, however due to this bug, some empty cgroup directories were remaining on the system. This update ensures that the notify_on_release functionality is always correctly triggered by correctly ordering operations in the cgroup_task_migrate() function.
BZ#963785
Previously, NFSv4 allowed an NFSv4 client to resume an expired or lost file lock. This could result in file corruption if the file was modified in the meantime. This problem has been resolved by a series of patches ensuring that an NFSv4 client no longer attempts to recover expired or lost file locks.
BZ#1036972
Systems that use NFS file systems could become unresponsive or trigger a kernel oops due to a use-after-free bug in the duplicate reply cache (DRC) code in the nfsd daemon. This problem has been resolved by modifying nfsd to unhash DRC entries before attempting to use them and to prefer to allocate a new DRC entry from the slab instead of reusing an expired entry from the list.
BZ#1036312
Inefficient usage of Big Kernel Locks (BKLs) in the ptrace() system call could lead to BKL contention on certain systems that widely utilize ptrace(), such as User-mode Linux (UML) systems, resulting in degraded performance on these systems. This update removes the relevant BKLs from the ptrace() system call, thus resolving any related performance issues.
BZ#975248
A bug in the ixgbe driver caused that IPv6 hardware filtering tables were not correctly rewritten upon interface reset when using a bridge device over the PF interface in an SR-IOV environment. As a result, the IPv6 traffic between VFs was interrupted. An upstream patch has been backported to modify the ixgbe driver so that the update of the Multimedia Terminal Adapter (MTA) table is now unconditional, avoiding possible inconsistencies in the MTA table upon PF's reset. The IPv6 traffic between VFs proceeds as expected in this scenario.
BZ#1116947
Later Intel CPUs added a new "Condition Changed" bit to the MSR_CORE_PERF_GLOBAL_STATUS register. Previously, the kernel falsely assumed that this bit indicates a performance interrupt, which prevented other NMI handlers from running and executing. To fix this problem, a patch has been applied to the kernel to ignore this bit in the perf code, enabling other NMI handlers to run.
BZ#975908
Due to a bug in the mlx4 driver, Mellanox Ethernet cards were brought down unexpectedly while adjusting their Tx or Rx ring. A patch has been applied so that the mlx4 driver now properly verifies the state of the Ethernet card when the coalescing of the Tx or Rx ring is being set, which resolves this problem.
BZ#1083748
Previously, hardware could execute commands send by drivers in FIFO order instead of tagged order. Commands thus could be executed out of sequence, which could result in large latencies and degradation of throughput. With this update, the ATA subsystem tags each command sent to the hardware, ensuring that the hardware executes commands in tagged order. Performance on controllers supporting tagged commands can now increase by 30-50%.
BZ#980188
When transferring a large amount of data over the peer-to-peer (PPP) link, a rare race condition between the throttle() and unthrottle() functions in the tty driver could be triggered. As a consequence, the tty driver became unresponsive, remaining in the throttled state, which resulted in the traffic being stalled. Also, if the PPP link was heavily loaded, another race condition in the tty driver could has been triggered. This race allowed an unsafe update of the available buffer space, which could also result in the stalled traffic. A series of patches addressing both race conditions has been applied to the tty driver; if the first race is triggered, the driver loops and forces re-evaluation of the respective test condition, which ensures uninterrupted traffic flow in the described situation. The second race is now completely avoided due to a well-placed read lock, and the update of the available buffer space proceeds correctly.
BZ#1086450
Previously, the Huge Translation Lookaside Buffer (HugeTLB) unconditionally allowed access to huge pages. However, huge pages may be unsupported in some environments, such as a KVM guest on the PowerPC architecture when not backed by huge pages, and an attempt to use a base page as a huge page in memory would result in a kernel oops. This update ensures that HugeTLB denies access to huge pages if the huge pages are not supported on the system.
BZ#982770
The restart logic for the memory reclaiming with compaction was previously applied on the level of LRU page vectors. This could, however, cause significant latency in memory allocation because memory compaction does not require only memory pages of a certain cgroup but a whole memory zone. This performance issue has been fixed by moving the restart logic to the zone level and restarting the memory reclaim for all memory cgroups in a zone when the compaction requires more free pages from the zone.
BZ#987634
A bug in the mlx4 driver could trigger a race between the "blue flame" feature's traffic flow and the stamping mechanism in the Tx ring flow when processing Work Queue Elements (WQEs) in the Tx ring. Consequently, the related queue pair (QP) of the mlx4 Ethernet card entered an error state and the traffic on the related Tx ring was blocked. A patch has been applied to the mlx4 driver so that the driver does not stamp the last completed WQE in the Tx ring, and thus avoids the aforementioned race.
BZ#1034269
When a page table is upgraded, a new top level of the page table is added for the virtual address space, which results in a new Address Space Control Element (ASCE). However, the Translation Lookaside Buffer (TLB) of the virtual address space was not previously flushed on page table upgrade. As a consequence, the TLB contained entries associated with the old ASCE which led to unexpected program failures and random data corruption. To correct this problem, the TLB entries associated with the old ASCE are now flushed as expected upon page table upgrade.
BZ#1034268
A previous change in the Linux memory management on IBM System z removed the handler for the Address Space Control Element (ASCE) type of exception. As a consequence, the kernel was unable to handle ASCE exceptions, which led to a kernel panic. Such an exception was triggered, for example, if the kernel attempted to access user memory with an address that was larger than the current page table limit from a user-space program. This problem has been fixed by calling the standard page fault handler, do_dat_exception, if an ASCE exception is raised.
BZ#1104268
Due to a bug in the mount option parser, prefix paths on a CIFS DFS share could be prepended with a double backslash ('\\'), resulting in an incorrect "No such file" error in certain environments. The mount option parser has been fixed and prefix paths now starts with a single backslash as expected.
BZ#995300
Due to a bug in the Infiniband driver, the ip and ifconfig utilities reported the link status of the IP over Infiniband (IPoIB) interfaces incorrectly (as "RUNNING" in case of "ifconfig", and as "UP" in case of "ip") even if no cable was connected to the respective network card. The problem has been corrected by calling the respective netif_carrier_off() function on the right place in the code. The link status of the IPoIB interfaces is now reported correctly in the described situation.
BZ#995576
An earlier patch to the kernel added the dynamic queue depth throttling functionality to the QLogic's qla2xxx driver that allowed the driver to adjust queue depth for attached SCSI devices. However, the kernel might have crashed when having this functionality enabled in certain environments, such as on systems with EMC PowerPath Multipathing installed that were under heavy I/O load. To resolve this problem, the dynamic queue depth throttling functionality has been removed from the qla2xxx driver.
BZ#1032350
A bug in the Completely Fair Scheduler (CFS) could, under certain circumstances, trigger a race condition while moving a forking task between cgroups. This race could lead to a free-after-use error and a subsequent kernel panic when a child task was accessed while it was pointing to a stale cgroup of its parent task. A patch has been applied to the CFS to ensure that a child task always points to the valid parent's task group.
BZ#998625
When performing I/O operations on a heavily-fragmented GFS2 file system, significant performance degradation could occur. This was caused by the allocation strategy that GFS2 used to search for an ideal contiguous chunk of free blocks in all the available resource groups (rgrp). A series of patches has been applied that improves performance of GFS2 file systems in case of heavy fragmentation. GFS2 now allocates the biggest extent found in the rgrp if it fulfills the minimum requirements. GFS2 has also reduced the amount of bitmap searching in case of multi-block reservations by keeping track of the smallest extent for which the multi-block reservation would fail in the given rgrp. This improves GFS2 performance by avoiding unnecessary rgrp free block searches that would fail. Additionally, this patch series fixes a bug in the GFS2 block allocation code where a multi-block reservation was not properly removed from the rgrp's reservation tree when it was disqualified, which eventually triggered a BUG_ON() macro due to an incorrect count of reserved blocks.
BZ#1032347
Due to a race condition in the cgroup code, the kernel task scheduler could trigger a use-after-free bug when it was moving an exiting task between cgroups, which resulted in a kernel panic. This update avoids the kernel panic by introducing a new function, cpu_cgroup_exit(). This function ensures that the kernel does not release a cgroup that is not empty yet.
BZ#1032343
Due to a race condition in the cgroup code, the kernel task scheduler could trigger a kernel panic when it was moving an exiting task between cgroups. A patch has been applied to avoid this kernel panic by replacing several improperly used function calls in the cgroup code.
BZ#1111631
The automatic route cache rebuilding feature could incorrectly compute the length of a route hash chain if the cache contained multiple entries with the same key but a different TOS, mark, or OIF bit. Consequently, the feature could reach the rebuild limit and disable the routing cache on the system. This problem is fixed by using a helper function that avoids counting such duplicate routes.
BZ#1093819
NFS previously called the drop_nlink() function after removing a file to directly decrease a link count on the related inode. Consequently, NFS did not revalidate an inode cache, and could thus use a stale file handle, resulting in an ESTALE error. A patch has been applied to ensure that NFS validates the inode cache correctly after removing a file.
BZ#1002727
Previously, the vmw_pwscsi driver could attempt to complete a command to the SCSI mid-layer after reporting a successful abort of the command. This led to a double completion bug and a subsequent kernel panic. This update ensures that the pvscsi_abort() function returns SUCCESS only after the abort is completed, preventing the driver from invalid attempts to complete the command.
BZ#1030094
Due to several bugs in the IPv6 code, a soft lockup could occur when the number of cached IPv6 destination entries reached the garbage collector treshold on a high-traffic router. A series of patches has been applied to address this problem. These patches ensure that the route probing is performed asynchronously to prevent a dead lock with garbage collection. Also, the garbage collector is now run asynchronously, preventing CPUs that concurrently requested the garbage collector from waiting until all other CPUs finish the garbage collection. As a result, soft lockups no longer occur in the described situation.
BZ#1030049
Due to a bug in the NFS code, the state manager and the DELEGRETURN operation could enter a deadlock if an asynchronous session error was received while DELEGRETURN was being processed by the state manager. The state manager became unable to process the failing DELEGRETURN operation because it was waiting for an asynchronous RPC task to complete, which could not have been completed because the DELEGRETURN operation was cycling indefinitely with session errors. A series of patches has been applied to ensure that the asynchronous error handler waits for recovery when a session error is received and the deadlock no longer occurs.
BZ#1030046
The RPC client always retransmitted zero-copy of the page data if it timed out before the first RPC transmission completed. However, such a retransmission could cause data corruption if using the O_DIRECT buffer and the first RPC call completed while the respective TCP socket still held a reference to the pages. To prevent the data corruption, retransmission of the RPC call is, in this situation, performed using the sendmsg() function. The sendmsg() function retransmits an authentic reproduction of the first RPC transmission because the TCP socket holds the full copy of the page data.
BZ#1095796
Due to a bug in the nouveau kernel module, the wrong display output could be modified in certain multi-display configurations. Consequently, on Lenovo Thinkpad T420 and W530 laptops with an external display connected, this could result in the LVDS panel "bleeding" to white during startup, and the display controller might become non-functional until after a reboot. Changes to the display configuration could also trigger the bug under various circumstances. With this update, the nouveau kernel module has been corrected and the said configurations now work as expected.
BZ#1007164
When guest supports Supervisor Mode Execution Protection (SMEP), KVM sets the appropriate permissions bits on the guest page table entries (sptes) to emulate SMEP enforced access. Previously, KVM was incorrectly verifying whether the "smep" bit was set in the host cr4 register instead of the guest cr4 register. Consequently, if the host supported SMEP, it was enforced even though it was not requested, which could render the guest system unbootable. This update corrects the said "smep" bit check and the guest system boot as expected in this scenario.
BZ#1029585
If a statically defined gateway became unreachable and its corresponding neighbor entry entered a FAILED state, the gateway stayed in the FAILED state even after it became reachable again. This prevented routing of the traffic through that gateway. This update allows probing such a gateway automatically and routing the traffic through the gateway again once it becomes reachable.
BZ#1009332
Previously, certain network device drivers did not accept ethtool commands right after they were mounted. As a consequence, the current setting of the specified device driver was not applied and an error message was returned. The ETHTOOL_DELAY variable has been added, which makes sure the ethtool utility waits for some time before it tries to apply the options settings, thus fixing the bug.
BZ#1009626
A system could enter a deadlock situation when the Real-Time (RT) scheduler was moving RT tasks between CPUs and the wakeup_kswapd() function was called on multiple CPUs, resulting in a kernel panic. This problem has been fixed by removing a problematic memory allocation and therefore calling the wakeup_kswapd() function from a deadlock-safe context.
BZ#1029530
Previously, the e752x_edac module incorrectly handled the pci_dev usage count, which could reach zero and deallocate a PCI device structure. As a consequence, a kernel panic could occur when the module was loaded multiple times on some systems. This update fixes the usage count that is triggered by loading and unloading the module repeatedly, and a kernel panic no longer occurs.
BZ#1011214
The IPv4 and IPv6 code contained several issues related to the conntrack fragmentation handling that prevented fragmented packages from being properly reassembled. This update applies a series of patches and ensures that MTU discovery is handled properly, and fragments are correctly matched and packets reassembled.
BZ#1028682
The kernel did not handle environmental and power warning (EPOW) interrupts correctly. This prevented successful usage of the "virsh shutdown" command to shut down guests on IBM POWER8 systems. This update ensures that the kernel handles EPOW events correctly and also prints informative descriptions for the respective EPOW events. The detailed information about each encountered EPOW can be found in the Real-Time Abstraction Service (RTAS) error log.
BZ#1097915
The bridge MDB RTNL handlers were incorrectly removed after deleting a bridge from the system with more then one bridge configured. This led to various problems, such as that the multicast IGMP snooping data from the remaining bridges were not displayed. This update ensures that the bridge handlers are removed only after the bridge module is unloaded, and the multicast IGMP snooping data now displays correctly in the described situation.
BZ#1098658
A previous change to the SCSI code fixed a race condition that could occur when removing a SCSI device. However, that change caused performance degradation because it used a certain function from the block layer code that was returning different values compared with later versions of the kernel. This update alters the SCSI code to properly utilize the values returned by the block layer code.
BZ#1026864
A previous change to the md driver disabled the TRIM operation for RAID5 volumes in order to prevent a possible kernel oops. However, if a MD RAID volume was reshaped to a different RAID level, this could result in TRIM being disabled on the resulting volume, as the RAID4 personality is used for certain reshapes. A patch has been applied that corrects this problem by setting the stacking limits before changing a RAID level, and thus ensuring the correct discard (TRIM) granularity for the RAID array.
BZ#1025439
As a result of a recent fix preventing a deadlock upon an attempt to cover an active XFS log, the behavior of the xfs_log_need_covered() function has changed. However, xfs_log_need_covered() is also called to ensure that the XFS log tail is correctly updated as a part of the XFS journal sync operation. As a consequence, when shutting down an XFS file system, the sync operation failed and some files might have been lost. A patch has been applied to ensure that the tail of the XFS log is updated by logging a dummy record to the XFS journal. The sync operation completes successfully and files are properly written to the disk in this situation.
BZ#1025224
There was an error in the tag insertion logic, and the bonding handled cases when a slave device did not have a hardware VLAN acceleration. As a consequence, network packets were tagged twice when passing through slave devices without hardware VLAN tag insertion, and network cards using a VLAN over a bonding device did not work properly. This update removes the redundant VLAN tag insertion logic, and the unwanted behavior no longer occurs.
BZ#1024683
Due to a bug in the Emulex lpfc driver, the driver could not allocate a SCSI buffer properly, which resulted in severe performance degradation of lpfc adapters on 64-bit PowerPC systems. A patch addressing this problem has been applied so that lpfc allocates the SCSI buffer correctly and lpfc adapters now work as expected on 64-bit PowerPC systems.
BZ#1024631
Previously, certain SELinux functions did not correctly handle the TCP synchronize-acknowledgment (SYN-ACK) packets when processing IPv4 labeled traffic over an INET socket. The initial SYN-ACK packets were labeled incorrectly by SELinux, and as a result, the access control decision was made using the server socket's label instead of the new connection's label. In addition, SELinux was not properly inspecting outbound labeled IPsec traffic, which led to similar problems with incorrect access control decisions. A series of patches that addresses these problems has been applied to SELinux. The initial SYN-ACK packets are now labeled correctly and SELinux processes all SYN-ACK packets as expected.
BZ#1100127
A previous change to the Open vSwitch kernel module introduced a use-after-free problem that resulted in a kernel panic on systems that use this module. This update ensures that the affected object is freed on the correct place in the code, thus avoiding the problem.
BZ#1024024
Previously, the GFS2 kernel module leaked memory in the gfs2_bufdata slab cache and allowed a use-after-free race condition to be triggered in the gfs2_remove_from_journal() function. As a consequence after unmounting the GFS2 file system, the GFS2 slab cache could still contain some objects, which subsequently could, under certain circumstances, result in a kernel panic. A series of patches has been applied to the GFS2 kernel module, ensuring that all objects are freed from the slab cache properly and the kernel panic is avoided.
BZ#1023897
A bug in the RSXX DMA handling code allowed DISCARD operations to call the pci_unmap_page() function, which triggered a race condition on the PowerPC architecture when DISCARD, READ, and WRITE operations were issued simultaneously. However, DISCARD operations are always assigned a DMA address of 0 because they are never mapped. Therefore, this race could result in freeing memory that was mapped for another operation and a subsequent EEH event. A patch has been applied, preventing the DISCARD operations from calling pci_unmap_page(), and thus avoiding the aforementioned race condition.
BZ#1023272
Due to a regression bug in the mlx4 driver, Mellanox mlx4 adapters could become unresponsive on heavy load along with IOMMU allocation errors being logged to the systems logs. A patch has been applied to the mlx4 driver so that the driver now calculates the last memory page fragment when allocating memory in the Rx path.
BZ#1021325
When performing read operations on an XFS file system, failed buffer readahead can leave the buffer in the cache memory marked with an error. This could lead to incorrect detection of stale errors during completion of an I/O operation because most callers do not zero out the b_error field of the buffer on a subsequent read. To avoid this problem and ensure correct I/O error detection, the b_error field of the used buffer is now zeroed out before submitting an I/O operation on a file.
BZ#1034237
Due to the locking mechanism that the kernel used while handling Out of Memory (OOM) situations in memory control groups (cgroups), the OOM killer did not work as intended in case that many processes triggered an OOM. As a consequence, the entire system could become or appear to be unresponsive. A series of patches has been applied to improve this locking mechanism so that the OOM killer now works as expected in memory cgroups under heavy OOM load.
BZ#1104503
Due to a bug in the GRE tunneling code, it was impossible to create a GRE tunnel with a custom name. This update corrects behavior of the ip_tunnel_find() function, allowing users to create GRE tunnels with custom names.
BZ#1020685
When the system was under memory stress, a double-free bug in the tg3 driver could have been triggered, resulting in a NIC being brought down unexpectedly followed by a kernel panic. A patch has been applied that restructures the respective code so that the affected ring buffer is freed correctly.
BZ#1021044
If the BIOS returned a negative value for the critical trip point for the given thermal zone during a system boot, the whole thermal zone was invalidated and an ACPI error was printed. However, the thermal zone may still have been needed for cooling. With this update, the ACPI thermal management has been modified to only disable the relevant critical trip point in this situation.
BZ#1020461
Due to a missing part of the bcma driver, the brcmsmac kernel module did not have a list of internal aliases that was needed by the kernel to properly handle the related udev events. Consequently, when the bcma driver scanned for the devices at boot time, these udev events were ignored and the kernel did not load the brcmsmac module automatically. A patch that provides missing aliases has been applied so that the udev requests of the brcmsmac module are now handled as expected and the kernel loads the brcmsmac module automatically on boot.
BZ#1103471
Previously, KVM did not accept PCI domain (segment) number for host PCI devices, making it impossible to assign a PCI device that was a part of a non-zero PCI segment to a virtual machine. To resolve this problem, KVM has been extended to accept PCI domain number in addition to slot, device, and function numbers.
BZ#1020290
Due to a bug in the EDAC driver, the driver failed to decode and report errors on AMD family 16h processors correctly. This update incorporates a missing case statement to the code so that the EDAC driver now handles errors as expected.
BZ#1019578
Previous changes to the igb driver caused the ethtool utility to determine and display some capabilities of the Ethernet devices incorrectly. This update fixes the igb driver so that the actual link capabilities are now determined properly, and ethtool displays values as accurate as possible in dependency on the data available to the driver.
BZ#1019346
Previously, devices using the ixgbevf driver that were assigned to a virtual machine could not adjust their Jumbo MTU value automatically if the Physical Function (PF) interface was down; when the PF device was brought up, the MTU value on the related Virtual Function (VF) device was set incorrectly. This was caused by the way the communication channel between PF and VF interfaces was set up and the first negotiation attempt between PF and VF was made. To fix this problem, structural changes to the ixgbevf driver have been made so that the kernel can now negotiate the correct API between PF and VF successfully and the MTU value is now set correctly on the VF interface in this situation.
BZ#1024006
A chunk of a patch was left out when backporting a batch of patches that fixed an infinite loop problem in the LOCK operation with zero state ID during NFSv4 state ID recovery. As a consequence, the system could become unresponsive on numerous occasions. The missing chunk of the patch has been added, resolving this hang issue.
BZ#1018138
The kernel previously did not reset the kernel ring buffer if the trace clock was changed during tracing. However, the new clock source could be inconsistent with the previous clock source, and the result trace record thus could contain incomparable time stamps. To ensure that the trace record contains only comparable time stamps, the ring buffer is now reset whenever the trace clock changes.
BZ#1024548
When using Haswell HDMI audio controllers with an unaligned DMA buffer size, these audio controllers could become locked up until the next reboot for certain audio stream configurations. A patch has been applied to the Intel's High Definition Audio (HDA) driver that enforces the DMA buffer alignment setting for the Haswell HDMI audio controllers. These audio controllers now work as expected.
BZ#1024689
A previous change to the virtual file system (VFS) code included the reduction of the PATH_MAX variable by 32 bytes. However, this change was not propagated to the do_getname() function, which had a negative impact on interactions between the getname() and do_getname() functions. This update modifies do_getname() accordingly and this function now works as expected.
BZ#1028372
Previously, when removing an IPv6 address from an interface, unreachable routes related to that address were not removed from the IPv6 routing table. This happened because the IPv6 code used inappropriate function when searching for the routes. To avoid this problem, the IPv6 code has been modified to use the ip6_route_lookup() function instead of rt6_lookup() in this situation. All related routes are now properly deleted from the routing tables when an IPv6 address is removed.
BZ#1029200
A bug in the statistics flow in the bnx2x driver caused the card's DMA Engine (DMAE) to be accessed without taking a necessary lock. As a consequence, previously queued DMAE commands could be overwritten and the Virtual Functions then could timeout on requests to their respective Physical Functions. The likelihood of triggering the bug was higher with more SR-IOV Virtual Functions configured. Overwriting of the DMAE commands could also result in other problems even without using SR-IOV. This update ensures that all flows utilizing DMAE will use the same API and the proper locking scheme is kept by all these flows.
BZ#1029203
The bnx2x driver handled unsupported TLVs received from a Virtual Function (VF) using the VF-PF channel incorrectly; when a driver of the VF sent a known but unsupported TLV command to the Physical Function, the driver of the PF did not reply. As a consequence, the VF-PF channel was left in an unstable state and the VF eventually timed out. A patch has been applied to correct the VF-PF locking scheme so that unsupported TLVs are properly handled and responded to by the PF side. Also, unsupported TLVs could previously render a mutex used to lock the VF-PF operations. The mutex then stopped protecting critical sections of the code, which could result in error messages being generated when the PF received additional TLVs from the VF. A patch has been applied that corrects the VF-PF channel locking scheme, and unsupported TLVs thus can no longer break the VF-PF lock.
BZ#1007039
When performing buffered WRITE operations from multiple processes to a single file, the NFS code previously always verified whether the lock owner information is identical for the file being accessed even though no file locks were involved. This led to performance degradation because forked child processes had to synchronize dirty data written to a disk by the parent process before writing to a file. Also, when coalescing requests into a single READ or WRITE RPC call, NFS refused the request if the lock owner information did not match for the given file even though no file locks were involved. This also caused performance degradation. A series of patches has been applied that relax relevant test conditions so that lock owner compatibility is no longer verified in the described cases, which resolves these performance issues.
BZ#1005491
Due to a previous change that altered the format of the txselect parameter, the InfiniBand qib driver was unable to support HP branded QLogic QDR InfiniBand cards in HP Blade servers. To resolve this problem, the driver's parsing routine, setup_txselect(), has been modified to handle multi-value strings.
BZ#994724
Due to a race condition that allowed a RAID array to be written to while it was being stopped, the md driver could enter a deadlock situation. The deadlock prevented buffers from being written out to the disk, and all I/O operations to the device became unresponsive. With this update, the md driver has been modified so this deadlock is now avoided.
BZ#1090423
Previously, recovery of a double-degraded RAID6 array could, under certain circumstances, result in data corruption. This could happen because the md driver was using an optimization that is safe to use only for single-degraded arrays. This update ensures that this optimization is skipped during the recovery of double-degraded RAID6 arrays.
BZ#1034348
NFS previously allowed a race between "silly rename" operations and the rmdir() function to occur when removing a directory right after an unlinked file in the directory was closed. As a result, rmdir() could fail with an EBUSY error. This update applies a patch ensuring that NFS waits for any asynchronous operations to complete before performing the rmdir() operation.
BZ#1034487
A deadlock between the state manager, kswapd daemon, and the sys_open() function could occur when the state manager was recovering from an expired state and recovery OPEN operations were being processed. To fix this problem, NFS has been modified to ignore all errors from the LAYOUTRETURN operation (a pNFS operation) except for "NFS4ERR_DELAY" in this situation.
BZ#980621
Previously, in certain environments, such as an HP BladeSystem Enclosure with several Blade servers, the kdump kernel could experience a kernel panic or become unresponsive during boot due to lack of available interrupt vectors. As a consequence, kdump failed to capture a core dump. To increase a number of available interrupt vectors, the kdump kernel can boot up with more CPUs. However, the kdump kernel always tries to boot up with the bootstrap processor (BSP), which can cause the kernel to fail to bring up more than one CPU under certain circumstances. This update introduces a new kernel parameter, disable_cpu_acipid, which allows the kdump kernel to disable BSP during boot and then to successfully boot up with multiple processors. This resolves the problem of lack of available interrupt vectors for systems with a high number of devices and ensures that kdump can now successfully capture a core dump on these systems.
BZ#1036814
The ext4_releasepage() function previously emitted an unnecessary warning message when it was passed a page with the PageChecked flag set. To avoid irrelevant warnings in the kernel log, this update removes the related WARN_ON() from the ext4 code.
BZ#960275
Previously, user space packet capturing libraries, such as libcap, had a limited possibility to determine which Berkeley Packet Filter (BPF) extensions are supported by the current kernel. This limitation had a negative effect on VLAN packet filtering that is performed by the tcpdump utility and tcpdump sometimes was not able to capture filtered packets correctly. Therefore, this update introduces a new option, SO_BPF_EXTENSIONS, which can be specified as an argument of the getsockopt() function. This option enables packet capturing tools to obtain information about which BPF extensions are supported by the current kernel. As a result, the tcpdump utility can now capture packets properly.
BZ#1081282
The RTM_NEWLINK messages can contain information about every virtual function (VF) for the given network interface (NIC) and can become very large if this information is not filtered. Previously, the kernel netlink interface allowed the getifaddr() function to process RTM_NEWLINK messages with unfiltered content. Under certain circumstances, the kernel netlink interface would omit data for the given group of NICs, causing getifaddr() to loop indefinitely being unable to return information about the affected NICs. This update resolves this problem by supplying only the RTM_NEWLINK messages with filtered content.
BZ#1040349
When booting a guest in the Hyper-V environment and enough of Programmable Interval Timer (PIT) interrupts were lost or not injected into the guest on time, the kernel panicked and the guest failed to boot. This problem has been fixed by bypassing the relevant PIT check when the guest is running under the Hyper-V environment.
BZ#1040393
The isci driver previously triggered an erroneous BUG_ON() assertion in case of a hard reset timeout in the sci_apc_agent_link_up() function. If a SATA device was unable to restore the link in time after the reset, the isci port had to return to the "awaiting link-up" state. However in such a case, the port may not have been in the "resetting" state, causing a kernel panic. This problem has been fixed by removing that incorrect BUG_ON() assertion.
BZ#1049052
Due to several bugs in the network console logging, a race condition between the network console send operation and the driver's IRQ handler could occur, or the network console could access invalid memory content. As a consequence, the respective driver, such as vmxnet3, triggered a BUG_ON() assertion and the system terminated unexpectedly. A patch addressing these bugs has been applied so that driver's IRQs are disabled before processing the send operation and the network console now accesses the RCU-protected (read-copy update) data properly. Systems using the network console logging no longer crashes due to the aforementioned conditions.
BZ#1057704
When a network interface is running in promiscuous (PROMISC) mode, the interface may receive and process VLAN-tagged frames even though no VLAN is attached to the interface. However, the enic driver did not handle processing of the packets with the VLAN-tagged frames in PROMISC mode correctly if the frames had no VLAN group assigned, which led to various problems. To handle the VLAN-tagged frames without a VLAN group properly, the frames have to be processed by the VLAN code, and the enic driver thus no longer verifies whether the packet's VLAN group field is empty.
BZ#1058528
The dm-bufio driver did not call the blk_unplug() function to flush plugged I/O requests. Therefore, the requests submitted by dm-bufio were delayed by 3 ms, which could cause performance degradation. With this update, dm-bufio calls blk_unplug() as expected, avoiding any related performance issues.
BZ#1059943
A previous change that modified the linkat() system call introduced a mount point reference leak and a subsequent memory leak in case that a file system link operation returned the ESTALE error code. These problems have been fixed by properly freeing the old mount point reference in such a case.
BZ#1062494
When allocating kernel memory, the SCSI device handlers called the sizeof() function with a structure name as its argument. However, the modified files were using an incorrect structure name, which resulted in an insufficient amount of memory being allocated and subsequent memory corruption. This update modifies the relevant sizeof() function calls to rather use a pointer to the structure instead of the structure name so that the memory is now always allocated correctly.
BZ#1065304
A previous patch to the kernel scheduler fixed a kernel panic caused by a divide-by-zero bug in the init_numa_sched_groups_power() function. However, that patch introduced a regression on systems with standard Non-Uniform Memory Access (NUMA) topology so that cpu_power in all but one NUMA domains was set to twice the expected value. This resulted in incorrect task scheduling and some processors being left idle even though there were enough queued tasks to handle, which had a negative impact on system performance. This update ensures that cpu_power on systems with standard NUMA topology is set to expected values by adding an estimate to cpu_power for every uncounted CPU.Task scheduling now works as expected on these systems without performance issues related to the said bug.
BZ#1018581
Microsoft Windows 7 KVM guests could become unresponsive during reboot because KVM did not manage to inject an Non-Maskable Interrupt (NMI) to the guest while the guest was running in user mode. To resolve this problem, a series of patches has been applied to the KVM code, ensuring that KVM handles NMIs correctly during the reboot of the guest machine.
BZ#1029381
Prior to this update, a guest-provided value was used as the head length of the socket buffer allocated on the host. If the host was under heavy memory load and the guest-provided value was too large, the allocation could have failed, resulting in stalls and packet drops in the guest's Tx path. With this update, the guest-provided value has been limited to a reasonable size so that socket buffer allocations on the host succeed regardless of the memory load on the host, and guests can send packets without experiencing packet drops or stalls.
BZ#1080637
The turbostat utility produced error messages when used on systems with the fourth generation of Intel Core Processors. To fix this problem, the kernel has been updated to provide the C-state residency information for the C8, C9, and C10 C-states.

Enhancements

BZ#876275
The kernel now supports memory configurations with more than 1TB of RAM on AMD systems.
BZ#990694
Users can now set ToS, TTL, and priority values in IPv4 on per-packet basis.
BZ#1038227
Several significant enhancements to device-mapper have been introduced in Red Hat Enterprise Linux 6.6:
  • The dm-cache device-mapper target, which allows fast storage devices to act as a cache for slower storage devices, has been added as a Technology Preview.
  • The device-mapper-multipath ALUA priority checker no longer places the preferred path device in its own path group if there are other paths that could be used for load balancing.
  • The fast_io_fail_tmo parameter in the multipath.conf file now works on iSCSI devices in addition to Fibre Channel devices.
  • Better performance can now be achieved in setups with a large number of multipath devices due to an improved way in which the device-mapper multipath handles sysfs files.
  • A new force_sync parameter in multipath.conf has been introduced. The parameter disables asynchronous path checks, which can help limit the number of CPU contention issues on setups with a large number of multipath devices.
BZ#922970
Support for the next generation of Intel's mobile platform has been added to Red Hat Enterprise Linux 6.6, and the relevant drivers have been updated.
BZ#922929
A future AMD processor provides a new bank of Model Specific Registers (MSRs) for L2 events which are be used for critical event types. These L2 cache performance counters are highly beneficial in performance and debugging.
BZ#1076147
The dm-crypt module has been modified to use multiple CPUs, which improves its encryption performance significantly.
BZ#1054299
The qla2xxx driver has been upgraded to version 8.05.00.03.06.5-k2, which provides a number of bug fixes over the previous version in order to correct various timeout problems with the mailbox command.
BZ#1053831
Keywords for the IPL device (ipldev) and console device (condev) on IBM System z has been enabled to ease the installation when the system uses the cio_ignore command to blacklist all devices at install time and does not have a default CCW console device number, has no devices other than the IPL device as a base to clone Linux guests, or with ramdisk based installations with no devices other than the CCW console.
BZ#872311
The cifs kernel module has been updated to handle FIPS mode cipher filtering efficiently in CIFS.
All Red Hat Enterprise Linux 6 users are advised to install these updated packages, which correct these issues, fix these bugs, and add these enhancements. The system must be rebooted for this update to take effect.