CVE-2021-47136

Public on

Last Modified: UTC

DescriptionAdditional informationCVSS Score DetailsWeakness (CWE)FAQ

Description

The CVE Program describes this issue as:

In the Linux kernel, the following vulnerability has been resolved: net: zero-initialize tc skb extension on allocation Function skb_ext_add() doesn't initialize created skb extension with any value and leaves it up to the user. However, since extension of type TC_SKB_EXT originally contained only single value tc_skb_ext->chain its users used to just assign the chain value without setting whole extension memory to zero first. This assumption changed when TC_SKB_EXT extension was extended with additional fields but not all users were updated to initialize the new fields which leads to use of uninitialized memory afterwards. UBSAN log: [ 778.299821] UBSAN: invalid-load in net/openvswitch/flow.c:899:28 [ 778.301495] load of value 107 is not a valid value for type '_Bool' [ 778.303215] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.12.0-rc7+ #2 [ 778.304933] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 [ 778.307901] Call Trace: [ 778.308680] <IRQ> [ 778.309358] dump_stack+0xbb/0x107 [ 778.310307] ubsan_epilogue+0x5/0x40 [ 778.311167] __ubsan_handle_load_invalid_value.cold+0x43/0x48 [ 778.312454] ? memset+0x20/0x40 [ 778.313230] ovs_flow_key_extract.cold+0xf/0x14 [openvswitch] [ 778.314532] ovs_vport_receive+0x19e/0x2e0 [openvswitch] [ 778.315749] ? ovs_vport_find_upcall_portid+0x330/0x330 [openvswitch] [ 778.317188] ? create_prof_cpu_mask+0x20/0x20 [ 778.318220] ? arch_stack_walk+0x82/0xf0 [ 778.319153] ? secondary_startup_64_no_verify+0xb0/0xbb [ 778.320399] ? stack_trace_save+0x91/0xc0 [ 778.321362] ? stack_trace_consume_entry+0x160/0x160 [ 778.322517] ? lock_release+0x52e/0x760 [ 778.323444] netdev_frame_hook+0x323/0x610 [openvswitch] [ 778.324668] ? ovs_netdev_get_vport+0xe0/0xe0 [openvswitch] [ 778.325950] __netif_receive_skb_core+0x771/0x2db0 [ 778.327067] ? lock_downgrade+0x6e0/0x6f0 [ 778.328021] ? lock_acquire+0x565/0x720 [ 778.328940] ? generic_xdp_tx+0x4f0/0x4f0 [ 778.329902] ? inet_gro_receive+0x2a7/0x10a0 [ 778.330914] ? lock_downgrade+0x6f0/0x6f0 [ 778.331867] ? udp4_gro_receive+0x4c4/0x13e0 [ 778.332876] ? lock_release+0x52e/0x760 [ 778.333808] ? dev_gro_receive+0xcc8/0x2380 [ 778.334810] ? lock_downgrade+0x6f0/0x6f0 [ 778.335769] __netif_receive_skb_list_core+0x295/0x820 [ 778.336955] ? process_backlog+0x780/0x780 [ 778.337941] ? mlx5e_rep_tc_netdevice_event_unregister+0x20/0x20 [mlx5_core] [ 778.339613] ? seqcount_lockdep_reader_access.constprop.0+0xa7/0xc0 [ 778.341033] ? kvm_clock_get_cycles+0x14/0x20 [ 778.342072] netif_receive_skb_list_internal+0x5f5/0xcb0 [ 778.343288] ? __kasan_kmalloc+0x7a/0x90 [ 778.344234] ? mlx5e_handle_rx_cqe_mpwrq+0x9e0/0x9e0 [mlx5_core] [ 778.345676] ? mlx5e_xmit_xdp_frame_mpwqe+0x14d0/0x14d0 [mlx5_core] [ 778.347140] ? __netif_receive_skb_list_core+0x820/0x820 [ 778.348351] ? mlx5e_post_rx_mpwqes+0xa6/0x25d0 [mlx5_core] [ 778.349688] ? napi_gro_flush+0x26c/0x3c0 [ 778.350641] napi_complete_done+0x188/0x6b0 [ 778.351627] mlx5e_napi_poll+0x373/0x1b80 [mlx5_core] [ 778.352853] __napi_poll+0x9f/0x510 [ 778.353704] ? mlx5_flow_namespace_set_mode+0x260/0x260 [mlx5_core] [ 778.355158] net_rx_action+0x34c/0xa40 [ 778.356060] ? napi_threaded_poll+0x3d0/0x3d0 [ 778.357083] ? sched_clock_cpu+0x18/0x190 [ 778.358041] ? __common_interrupt+0x8e/0x1a0 [ 778.359045] __do_softirq+0x1ce/0x984 [ 778.359938] __irq_exit_rcu+0x137/0x1d0 [ 778.360865] irq_exit_rcu+0xa/0x20 [ 778.361708] common_interrupt+0x80/0xa0 [ 778.362640] </IRQ> [ 778.363212] asm_common_interrupt+0x1e/0x40 [ 778.364204] RIP: 0010:native_safe_halt+0xe/0x10 [ 778.365273] Code: 4f ff ff ff 4c 89 e7 e8 50 3f 40 fe e9 dc fe ff ff 48 89 df e8 43 3f 40 fe eb 90 cc e9 07 00 00 00 0f 00 2d 74 05 62 00 fb f4 <c3> 90 e9 07 00 00 00 0f 00 2d 64 05 62 00 f4 c3 cc cc 0f 1f 44 00 [ 778.369355] RSP: 0018:ffffffff84407e48 EFLAGS: 00000246 [ 778.370570] RAX ---truncated---

Additional information

  • Bugzilla 2271498: kernel: net: zero-initialize tc skb extension on allocation
  • CWE-20: Improper Input Validation
  • FAQ: Frequently asked questions about CVE-2021-47136

Common Vulnerability Scoring System (CVSS) Score Details

Important note

CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).

The following CVSS metrics and score provided are preliminary and subject to review.

CVSS v3 Score Breakdown
Red HatNVD

CVSS v3 Base Score

4.4

5.5

Attack Vector

Local

Local

Attack Complexity

Low

Low

Privileges Required

High

Low

User Interaction

None

None

Scope

Unchanged

Unchanged

Confidentiality Impact

None

None

Integrity Impact

None

None

Availability Impact

High

High

CVSS v3 Vector

Red Hat: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Frequently Asked Questions

Why is Red Hat's CVSS v3 score or Impact different from other vendors?

For open source software shipped by multiple vendors, the CVSS base scores may vary for each vendor's version depending on the version they ship, how they ship it, the platform, and even how the software is compiled. This makes scoring of vulnerabilities difficult for third-party vulnerability databases such as NVD that only provide a single CVSS base score for each vulnerability. Red Hat scores reflect how a vulnerability affects our products specifically.

For more information, see https://access.redhat.com/solutions/762393.

My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?

  • "Under investigation" doesn't necessarily mean that the product is affected by this vulnerability. It only means that our Analysis Team is still working on determining whether the product is affected and how it is affected.
  • The term "Affected" means that our Analysis team has determined that this product, such as Red Hat Enterprise Linux 8 or OpenShift Container Platform 4, is affected by this vulnerability and a fix may be released to address this issue in the near future. This includes all minor releases of this product unless noted otherwise in the Statement text.

What can I do if my product is listed as "Will not fix"?

A "will not fix" status means that a fix for an affected product version is not planned or not possible due to complexity, which may create additional risk.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Upgrade to a supported product version that includes a fix for this vulnerability (recommended).
  • Apply a mitigation (if one exists).
  • Open a support case to request a prioritization of releasing a fix for this vulnerability.

What can I do if my product is listed as "Fix deferred"?

A deferred status means that a fix for an affected product version is not guaranteed due to higher-priority development work.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Apply a mitigation (if one exists).
  • Open a support case to request a prioritization of releasing a fix for this vulnerability.
  • Red Hat Engineering focuses on addressing high-priority issues based on their complexity or limited lifecycle support. Therefore, lower-priority issues will not receive immediate fixes.

What is a mitigation?

A mitigation is an action that can be taken to reduce the impact of a security vulnerability, without deploying any fixes.

I have a Red Hat product but it is not in the above list, is it affected?

The listed products were found to include one or more of the components that this vulnerability affects. These products underwent a thorough evaluation to determine their affectedness by this vulnerability. Note that layered products (such as container-based offerings) that consume affected components from any of the products listed in this table may be affected and are not represented.

Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?

In order to maintain code stability and compatibility, Red Hat usually does not rebase packages to entirely new versions. Instead, we backport fixes and new features to an older version of the package we distribute. This can result in some security scanners that only consider the package version to report the package as vulnerable. To avoid this, we suggest that you use an approved vulnerability scanner from our Red Hat Vulnerability Scanner Certification program.

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