f2fs: fix to avoid racing on fsync_entry_slab by multi filesystem instances (CVE-2021-47335) | HOL Guard CVE

Medium · CVSS 5.5CVE-2021-47335

f2fs: fix to avoid racing on fsync_entry_slab by multi filesystem instances

Answer in brief

CVE-2021-47335 records a Medium severity (CVSS 5.5) vulnerability in f2fs: fix to avoid racing on fsync_entry_slab by multi filesystem instances. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published May 21, 2024Updated Aug 11, 2026Source checked Sep 25, 2026First seen by HOL Aug 11, 2026Material review Aug 11, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 5.5
Exploitation: Not marked as known exploited
Affected software: 3 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 5.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:o:linux:linux_kernel::::::::	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=d624c96fb3249e5d3dcf4e60a805e5e6b0dd7d91 <86786603014e0a22d0d6af8e80ae4b8687927048 \|\| >=d624c96fb3249e5d3dcf4e60a805e5e6b0dd7d91 <79fa5d944c875711253a23b8155b36883c696409 \|\| >=d624c96fb3249e5d3dcf4e60a805e5e6b0dd7d91 <e472b276a0d2180808009be38105e12754432e2a \|\| >=d624c96fb3249e5d3dcf4e60a805e5e6b0dd7d91 <cad83c968c2ebe97905f900326988ed37146c347	86786603014e0a22d0d6af8e80ae4b8687927048, 79fa5d944c875711253a23b8155b36883c696409, e472b276a0d2180808009be38105e12754432e2a, cad83c968c2ebe97905f900326988ed37146c347
Linux/Linuxgeneric	3.8	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to 86786603014e0a22d0d6af8e80ae4b8687927048 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
May 21, 2024
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 11, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 11, 2026

Sources and claim methodology

Upstream source description

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to avoid racing on fsync_entry_slab by multi filesystem instances As syzbot reported, there is an use-after-free issue during f2fs recovery: Use-after-free write at 0xffff88823bc16040 (in kfence-#10): kmem_cache_destroy+0x1f/0x120 mm/slab_common.c:486 f2fs_recover_fsync_data+0x75b0/0x8380 fs/f2fs/recovery.c:869 f2fs_fill_super+0x9393/0xa420 fs/f2fs/super.c:3945 mount_bdev+0x26c/0x3a0 fs/super.c:1367 legacy_get_tree+0xea/0x180 fs/fs_context.c:592 vfs_get_tree+0x86/0x270 fs/super.c:1497 do_new_mount fs/namespace.c:2905 [inline] path_mount+0x196f/0x2be0 fs/namespace.c:3235 do_mount fs/namespace.c:3248 [inline] __do_sys_mount fs/namespace.c:3456 [inline] __se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3433 do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae The root cause is multi f2fs filesystem instances can race on accessing global fsync_entry_slab pointer, result in use-after-free issue of slab cache, fixes to init/destroy this slab cache only once during module init/destroy procedure to avoid this issue.

Quoted source text, attributed separately from HOL analysis.