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CVE Record

CVE-2025-38626: f2fs: fix to trigger foreground gc during f2fs_map_blocks() in lfs mode

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to trigger foreground gc during f2fs_map_blocks() in lfs mode w/ "mode=lfs" mount option, generic/299 will cause system panic as below: ------------[ cut here ]------------ kernel BUG at fs/f2fs/segment.c:2835! Call Trace: <TASK> f2fs_allocate_data_block+0x6f4/0xc50 f2fs_map_blocks+0x970/0x1550 f2fs_iomap_begin+0xb2/0x1e0 iomap_iter+0x1d6/0x430 __iomap_dio_rw+0x208/0x9a0 f2fs_file_write_iter+0x6b3/0xfa0 aio_write+0x15d/0x2e0 io_submit_one+0x55e/0xab0 __x64_sys_io_submit+0xa5/0x230 do_syscall_64+0x84/0x2f0 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0010:new_curseg+0x70f/0x720 The root cause of we run out-of-space is: in f2fs_map_blocks(), f2fs may trigger foreground gc only if it allocates any physical block, it will be a little bit later when there is multiple threads writing data w/ aio/dio/bufio method in parallel, since we always use OPU in lfs mode, so f2fs_map_blocks() does block allocations aggressively. In order to fix this issue, let's give a chance to trigger foreground gc in prior to block allocation in f2fs_map_blocks().

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2025-38626 is a Linux kernel F2FS bug that can panic a system when F2FS is mounted with mode=lfs and concurrent writes exhaust space handling. The business impact is availability: affected systems may crash under specific storage and workload conditions.

Executive priority

Prioritize patching where F2FS is used for production storage or availability-sensitive systems. General fleet urgency is lower if F2FS mode=lfs is not deployed, but confirm rather than assume.

Technical view

The fix changes f2fs_map_blocks() so foreground garbage collection can run before block allocation in LFS mode. The source describes aggressive block allocation with parallel AIO, DIO, or buffered writes leading to out-of-space behavior and a kernel BUG in segment.c.

Likely exposure

Exposure appears limited to Linux systems using the F2FS filesystem with the mode=lfs mount option, especially under concurrent write workloads. The CVE record lists multiple Linux kernel version lines as affected, but downstream distribution status must be checked with the vendor.

Exploitation context

The provided sources do not show active exploitation, public exploit code, or KEV listing. The trigger evidence is a filesystem stress case causing system panic, not a documented remote attack path.

Researcher notes

Evidence is limited to the CVE record and kernel stable references. No CVSS, CWE, exploitability details, or downstream vendor matrix is provided. Treat impact as local availability risk unless additional vendor evidence expands the scope.

Mitigation direction

  • Update to a kernel or distribution package containing the referenced F2FS stable fixes.
  • Check Linux distribution advisories for the exact backported fixed package version.
  • Review systems using F2FS with the mode=lfs mount option.
  • If patching is delayed, avoid high-concurrency writes on affected F2FS LFS mounts where feasible.

Validation and detection

  • Inventory Linux hosts and identify F2FS filesystems mounted with mode=lfs.
  • Compare running kernel versions against distribution advisories and fixed stable commits.
  • Review crash logs for F2FS, f2fs_map_blocks, segment.c, or kernel BUG signatures.
  • Confirm patched systems no longer run affected kernel builds.
Prepared
Confidence
medium
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
8Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux36abef4e796d382e81a0c2d21ea5327481dd7154, 36abef4e796d382e81a0c2d21ea5327481dd7154, 36abef4e796d382e81a0c2d21ea5327481dd7154, 36abef4e796d382e81a0c2d21ea5327481dd7154, 36abef4e796d382e81a0c2d21ea5327481dd7154, 36abef4e796d382e81a0c2d21ea5327481dd7154, 36abef4e796d382e81a0c2d21ea5327481dd7154unaffected
LinuxLinux4.8, 0, 5.15.209, 6.1.167, 6.6.102, 6.12.42, 6.15.10, 6.16.1, 6.17affected
Weakness

CWE details

No CWE listed

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