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CVE-2021-46982

f2fs: compress: fix race condition of overwrite vs truncate

MEDIUM
4.7
CVSS Score
Published: February 28, 2024 at 08:13 AM UTC
Updated: June 17, 2026 at 04:16 AM UTC
1 product affected across 1 vendorLinux Kernel

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Severity
MEDIUM4.7
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Linux Kernel· Linux
95%
5.11 ≤ v < 5.11.225.12 ≤ v < 5.12.55.6 ≤ v < 5.10.385.6 ≤ v < 5.11.225.6 ≤ v < 5.12.55.6 ≤ v < 5.134c8ff7095bef64fc47e996a938f7d57f9e077da35.13 rc1
Vendor states this is fixed in 5639b73fd3bc6fc8ca72e3a9ac15aacaabd7ebff (fixed)
Vendor states this is fixed in 64acb100fe3beb5d20184d0ae3307235bd3555c4 (fixed)
Vendor states this is fixed in 936158b15e2648253afb824d252c910c496d34b5 (fixed)
Vendor states this is fixed in a949dc5f2c5cfe0c910b664650f45371254c0744 (fixed)
Vendor states this is fixed in 5.10.38 (unaffected)
Vendor states this is fixed in 5.11.22 (unaffected)
Vendor states this is fixed in 5.12.5 (unaffected)
Vendor states this is fixed in 5.13 (unaffected)
Vendor states this is fixed in 5.6 (unaffected)

References (4)

Patch
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/5639b73fd3bc6fc8ca72e3a9ac15aacaabd7ebff
Patch
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/64acb100fe3beb5d20184d0ae3307235bd3555c4
Patch
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/936158b15e2648253afb824d252c910c496d34b5
Patch
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/a949dc5f2c5cfe0c910b664650f45371254c0744

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.7MEDIUM[email protected]
Attack Vector
LOCAL
Complexity
HIGH
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-362

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