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CVE-2026-23233— f2fs: fix to avoid mapping wrong physical block for swapfile

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于check_swap_activate函数映射错误的物理块，可能导致数据损坏。

AI Predicted 7.8 Difficulty: Moderate EPSS 0.16% · P5

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 13

VendorProduct Version RangeStatus
Linux Linux 40d76c393cca83938b11eb7ca8983aa3cd0ed69b< d4534a7f6c92baaf7e12a45fc6e37332cafafc33 affected
9703d69d9d153bb230711d0d577454552aeb13d4< 1ff415eef513bf12deb058fc50d57788c46c48e6 affected
9703d69d9d153bb230711d0d577454552aeb13d4< fee27b69dde1a05908b350eea42937af2387c4fe affected
9703d69d9d153bb230711d0d577454552aeb13d4< 607cb9d83838d2cd9f0406c2403ed61aadf0edff affected
9703d69d9d153bb230711d0d577454552aeb13d4< 5c145c03188bc9ba1c29e0bc4d527a5978fc47f9 affected
6.6.33< 6.6.127 affected
6.9 affected
< 6.9 unaffected
… +5 more rows
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I. Basic Information for CVE-2026-23233

Vulnerability Information
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Vulnerability Title
f2fs: fix to avoid mapping wrong physical block for swapfile
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于check_swap_activate函数映射错误的物理块，可能导致数据损坏。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 40d76c393cca83938b11eb7ca8983aa3cd0ed69b ~ d4534a7f6c92baaf7e12a45fc6e37332cafafc33 -
Linux Linux 6.9 -

II. Public POCs for CVE-2026-23233

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III. Intelligence Information for CVE-2026-23233

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Patches & Fixes for CVE-2026-23233 (5)

Same Patch Batch · Linux · 2026-03-04 · 9 CVEs total

CVE-2026-23231 7.8 HIGH netfilter: nf_tables: fix use-after-free in nf_tables_addchain()
CVE-2026-23236 7.3 HIGH fbdev: smscufx: properly copy ioctl memory to kernelspace
CVE-2026-23232 Revert "f2fs: block cache/dio write during f2fs_enable_checkpoint()"
CVE-2025-71238 scsi: qla2xxx: Fix bsg_done() causing double free
CVE-2026-23234 f2fs: fix to avoid UAF in f2fs_write_end_io()
CVE-2026-23235 f2fs: fix out-of-bounds access in sysfs attribute read/write
CVE-2026-23238 romfs: check sb_set_blocksize() return value
CVE-2026-23237 platform/x86: classmate-laptop: Add missing NULL pointer checks

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-23233

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