4.7

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.
Data is provided by the National Vulnerability Database (NVD)
Linux ≫ Linux Kernel Version >= 5.6 < 5.10.38
Linux ≫ Linux Kernel Version >= 5.11 < 5.11.22
Linux ≫ Linux Kernel Version >= 5.12 < 5.12.5
Linux ≫ Linux Kernel Version5.13 Updaterc1
Zu dieser CVE wurde keine CISA KEV oder CERT.AT-Warnung gefunden.
EPSS Metriken
Type Source Score Percentile
EPSS FIRST.org 0.02% 0.026
CVSS Metriken
Source Base Score Exploit Score Impact Score Vector string
nvd@nist.gov 4.7 1 3.6
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

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.