CVE-2023-52705
Description
From CVE.org
In the Linux kernel, the following vulnerability has been resolved: nilfs2: fix underflow in second superblock position calculations Macro NILFS_SB2_OFFSET_BYTES, which computes the position of the second superblock, underflows when the argument device size is less than 4096 bytes. Therefore, when using this macro, it is necessary to check in advance that the device size is not less than a lower limit, or at least that underflow does not occur. The current nilfs2 implementation lacks this check, causing out-of-bound block access when mounting devices smaller than 4096 bytes: I/O error, dev loop0, sector 36028797018963960 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2 NILFS (loop0): unable to read secondary superblock (blocksize = 1024) In addition, when trying to resize the filesystem to a size below 4096 bytes, this underflow occurs in nilfs_resize_fs(), passing a huge number of segments to nilfs_sufile_resize(), corrupting parameters such as the number of segments in superblocks. This causes excessive loop iterations in nilfs_sufile_resize() during a subsequent resize ioctl, causing semaphore ns_segctor_sem to block for a long time and hang the writer thread: INFO: task segctord:5067 blocked for more than 143 seconds. Not tainted 6.2.0-rc8-syzkaller-00015-gf6feea56f66d #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:segctord state:D stack:23456 pid:5067 ppid:2 flags:0x00004000 Call Trace: <TASK> context_switch kernel/sched/core.c:5293 [inline] __schedule+0x1409/0x43f0 kernel/sched/core.c:6606 schedule+0xc3/0x190 kernel/sched/core.c:6682 rwsem_down_write_slowpath+0xfcf/0x14a0 kernel/locking/rwsem.c:1190 nilfs_transaction_lock+0x25c/0x4f0 fs/nilfs2/segment.c:357 nilfs_segctor_thread_construct fs/nilfs2/segment.c:2486 [inline] nilfs_segctor_thread+0x52f/0x1140 fs/nilfs2/segment.c:2570 kthread+0x270/0x300 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308 </TASK> ... Call Trace: <TASK> folio_mark_accessed+0x51c/0xf00 mm/swap.c:515 __nilfs_get_page_block fs/nilfs2/page.c:42 [inline] nilfs_grab_buffer+0x3d3/0x540 fs/nilfs2/page.c:61 nilfs_mdt_submit_block+0xd7/0x8f0 fs/nilfs2/mdt.c:121 nilfs_mdt_read_block+0xeb/0x430 fs/nilfs2/mdt.c:176 nilfs_mdt_get_block+0x12d/0xbb0 fs/nilfs2/mdt.c:251 nilfs_sufile_get_segment_usage_block fs/nilfs2/sufile.c:92 [inline] nilfs_sufile_truncate_range fs/nilfs2/sufile.c:679 [inline] nilfs_sufile_resize+0x7a3/0x12b0 fs/nilfs2/sufile.c:777 nilfs_resize_fs+0x20c/0xed0 fs/nilfs2/super.c:422 nilfs_ioctl_resize fs/nilfs2/ioctl.c:1033 [inline] nilfs_ioctl+0x137c/0x2440 fs/nilfs2/ioctl.c:1301 ... This fixes these issues by inserting appropriate minimum device size checks or anti-underflow checks, depending on where the macro is used.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert: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 Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | 5.5 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/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
Understanding the Weakness (CWE)
Integrity,Availability
Technical Impact: Modify Memory; DoS: Crash, Exit, or Restart
Out of bounds memory access will very likely result in the corruption of relevant memory, and perhaps instructions, possibly leading to a crash.
Integrity,Confidentiality,Availability,Access Control,Other
Technical Impact: Execute Unauthorized Code or Commands; Modify Memory; Bypass Protection Mechanism; Other
If the corrupted memory can be effectively controlled, it may be possible to execute arbitrary code. If the corrupted memory is data rather than instructions, the system will continue to function with improper changes, possibly in violation of an implicit or explicit policy. The consequences would only be limited by how the affected data is used, such as an adjacent memory location that is used to specify whether the user has special privileges.
Access Control,Other
Technical Impact: Bypass Protection Mechanism; Other
When the consequence is arbitrary code execution, this can often be used to subvert any other security service.
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