Vulnerability Details : CVE-2021-46982
In the Linux kernel, the following vulnerability has been resolved:
f2fs: compress: fix race condition of overwrite vs truncate
pos_fsstress testcase complains a panic as belew:
------------[ cut here ]------------
kernel BUG at fs/f2fs/compress.c:1082!
invalid opcode: 0000 [#1] SMP PTI
CPU: 4 PID: 2753477 Comm: kworker/u16:2 Tainted: G OE 5.12.0-rc1-custom #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
Workqueue: writeback wb_workfn (flush-252:16)
RIP: 0010:prepare_compress_overwrite+0x4c0/0x760 [f2fs]
Call Trace:
f2fs_prepare_compress_overwrite+0x5f/0x80 [f2fs]
f2fs_write_cache_pages+0x468/0x8a0 [f2fs]
f2fs_write_data_pages+0x2a4/0x2f0 [f2fs]
do_writepages+0x38/0xc0
__writeback_single_inode+0x44/0x2a0
writeback_sb_inodes+0x223/0x4d0
__writeback_inodes_wb+0x56/0xf0
wb_writeback+0x1dd/0x290
wb_workfn+0x309/0x500
process_one_work+0x220/0x3c0
worker_thread+0x53/0x420
kthread+0x12f/0x150
ret_from_fork+0x22/0x30
The root cause is truncate() may race with overwrite as below,
so that one reference count left in page can not guarantee the
page attaching in mapping tree all the time, after truncation,
later find_lock_page() may return NULL pointer.
- prepare_compress_overwrite
- f2fs_pagecache_get_page
- unlock_page
- f2fs_setattr
- truncate_setsize
- truncate_inode_page
- delete_from_page_cache
- find_lock_page
Fix this by avoiding referencing updated page.
Products affected by CVE-2021-46982
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:5.13:rc1:*:*:*:*:*:*
Exploit prediction scoring system (EPSS) score for CVE-2021-46982
0.04%
Probability of exploitation activity in the next 30 days
EPSS Score History
~ 5 %
Percentile, the proportion of vulnerabilities that are scored at or less
CVSS scores for CVE-2021-46982
Base Score | Base Severity | CVSS Vector | Exploitability Score | Impact Score | Score Source | First Seen |
---|---|---|---|---|---|---|
4.7
|
MEDIUM | CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H |
1.0
|
3.6
|
NIST | 2024-12-31 |
CWE ids for CVE-2021-46982
-
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.Assigned by: nvd@nist.gov (Primary)
References for CVE-2021-46982
-
https://git.kernel.org/stable/c/5639b73fd3bc6fc8ca72e3a9ac15aacaabd7ebff
f2fs: compress: fix race condition of overwrite vs truncate - kernel/git/stable/linux.git - Linux kernel stable treePatch
-
https://git.kernel.org/stable/c/a949dc5f2c5cfe0c910b664650f45371254c0744
f2fs: compress: fix race condition of overwrite vs truncate - kernel/git/stable/linux.git - Linux kernel stable treePatch
-
https://git.kernel.org/stable/c/936158b15e2648253afb824d252c910c496d34b5
f2fs: compress: fix race condition of overwrite vs truncate - kernel/git/stable/linux.git - Linux kernel stable treePatch
-
https://git.kernel.org/stable/c/64acb100fe3beb5d20184d0ae3307235bd3555c4
f2fs: compress: fix race condition of overwrite vs truncate - kernel/git/stable/linux.git - Linux kernel stable treePatch
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