In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix to avoid mapping wrong physical block for swapfile
Xiaolong Guo reported a f2fs bug in bugzilla [1]
[1] https://bugzilla.kernel.org/show_bug.cgi?id=220951
Quoted:
"When using stress-ng's swap stress test on F2FS filesystem with kernel 6.6+,
the system experiences data corruption leading to either:
1 dm-verity corruption errors and device reboot
2 F2FS node corruption errors and boot hangs
The issue occurs specifically when:
1 Using F2FS filesystem (ext4 is unaffected)
2 Swapfile size is less than F2FS section size (2MB)
3 Swapfile has fragmented physical layout (multiple non-contiguous extents)
4 Kernel version is 6.6+ (6.1 is unaffected)
The root cause is in check_swap_activate() function in fs/f2fs/data.c. When the
first extent of a small swapfile (< 2MB) is not aligned to section boundaries,
the function incorrectly treats it as the last extent, failing to map
subsequent extents. This results in incorrect swap_extent creation where only
the first extent is mapped, causing subsequent swap writes to overwrite wrong
physical locations (other files' data).
Steps to Reproduce
1 Setup a device with F2FS-formatted userdata partition
2 Compile stress-ng from https://github.com/ColinIanKing/stress-ng
3 Run swap stress test: (Android devices)
adb shell "cd /data/stressng; ./stress-ng-64 --metrics-brief --timeout 60
--swap 0"
Log:
1 Ftrace shows in kernel 6.6, only first extent is mapped during second
f2fs_map_blocks call in check_swap_activate():
stress-ng-swap-8990: f2fs_map_blocks: ino=11002, file offset=0, start
blkaddr=0x43143, len=0x1
(Only 4KB mapped, not the full swapfile)
2 in kernel 6.1, both extents are correctly mapped:
stress-ng-swap-5966: f2fs_map_blocks: ino=28011, file offset=0, start
blkaddr=0x13cd4, len=0x1
stress-ng-swap-5966: f2fs_map_blocks: ino=28011, file offset=1, start
blkaddr=0x60c84b, len=0xff
The problematic code is in check_swap_activate():
if ((pblock - SM_I(sbi)->main_blkaddr) % blks_per_sec ||
nr_pblocks % blks_per_sec ||
!f2fs_valid_pinned_area(sbi, pblock)) {
bool last_extent = false;
not_aligned++;
nr_pblocks = roundup(nr_pblocks, blks_per_sec);
if (cur_lblock + nr_pblocks > sis->max)
nr_pblocks -= blks_per_sec;
/* this extent is last one */
if (!nr_pblocks) {
nr_pblocks = last_lblock - cur_lblock;
last_extent = true;
}
ret = f2fs_migrate_blocks(inode, cur_lblock, nr_pblocks);
if (ret) {
if (ret == -ENOENT)
ret = -EINVAL;
goto out;
}
if (!last_extent)
goto retry;
}
When the first extent is unaligned and roundup(nr_pblocks, blks_per_sec)
exceeds sis->max, we subtract blks_per_sec resulting in nr_pblocks = 0. The
code then incorrectly assumes this is the last extent, sets nr_pblocks =
last_lblock - cur_lblock (entire swapfile), and performs migration. After
migration, it doesn't retry mapping, so subsequent extents are never processed.
"
In order to fix this issue, we need to lookup block mapping info after
we migrate all blocks in the tail of swapfile.
References
Configurations
Configuration 1 (hide)
|
History
17 Mar 2026, 21:21
| Type | Values Removed | Values Added |
|---|---|---|
| CVSS |
v2 : v3 : |
v2 : unknown
v3 : 7.8 |
| First Time |
Linux
Linux linux Kernel |
|
| References | () https://git.kernel.org/stable/c/1ff415eef513bf12deb058fc50d57788c46c48e6 - Patch | |
| References | () https://git.kernel.org/stable/c/5c145c03188bc9ba1c29e0bc4d527a5978fc47f9 - Patch | |
| References | () https://git.kernel.org/stable/c/607cb9d83838d2cd9f0406c2403ed61aadf0edff - Patch | |
| References | () https://git.kernel.org/stable/c/d4534a7f6c92baaf7e12a45fc6e37332cafafc33 - Patch | |
| References | () https://git.kernel.org/stable/c/fee27b69dde1a05908b350eea42937af2387c4fe - Patch | |
| Summary |
|
|
| CWE | CWE-787 | |
| CPE | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
04 Mar 2026, 15:16
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-03-04 15:16
Updated : 2026-03-17 21:21
NVD link : CVE-2026-23233
Mitre link : CVE-2026-23233
CVE.ORG link : CVE-2026-23233
JSON object : View
Products Affected
linux
- linux_kernel
CWE
CWE-787
Out-of-bounds Write