f2fs: fix use-after-free of sbi in f2fs_compress_write_end_io()

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Summary

CVECVE-2026-31702
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-01 14:16:20 UTC
Updated2026-06-01 17:16:56 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: f2fs: fix use-after-free of sbi in f2fs_compress_write_end_io() In f2fs_compress_write_end_io(), dec_page_count(sbi, type) can bring the F2FS_WB_CP_DATA counter to zero, unblocking f2fs_wait_on_all_pages() in f2fs_put_super() on a concurrent unmount CPU. The unmount path then proceeds to call f2fs_destroy_page_array_cache(sbi), which destroys sbi->page_array_slab via kmem_cache_destroy(), and eventually kfree(sbi). Meanwhile, the bio completion callback is still executing: when it reaches page_array_free(sbi, ...), it dereferences sbi->page_array_slab — a destroyed slab cache — to call kmem_cache_free(), causing a use-after-free. This is the same class of bug as CVE-2026-23234 (which fixed the equivalent race in f2fs_write_end_io() in data.c), but in the compressed writeback completion path that was not covered by that fix. Fix this by moving dec_page_count() to after page_array_free(), so that all sbi accesses complete before the counter decrement that can unblock unmount. For non-last folios (where atomic_dec_return on cic->pending_pages is nonzero), dec_page_count is called immediately before returning — page_array_free is not reached on this path, so there is no post-decrement sbi access. For the last folio, page_array_free runs while the F2FS_WB_CP_DATA counter is still nonzero (this folio has not yet decremented it), keeping sbi alive, and dec_page_count runs as the final operation.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.000180000 probability, percentile 0.048290000 (date 2026-05-05)

Problem Types: CWE-416

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 4c8ff7095bef64fc47e996a938f7d57f9e077da3 57bc678f36ac03281e877c6b84877b43f964143f git Not specified
CNA Linux Linux affected 4c8ff7095bef64fc47e996a938f7d57f9e077da3 ef57cd3329b40c739b9a2e1a8a21ecc4171c6280 git Not specified
CNA Linux Linux affected 4c8ff7095bef64fc47e996a938f7d57f9e077da3 f5154cf3ce1c8193f0c1891d3769f62740cfe6fe git Not specified
CNA Linux Linux affected 4c8ff7095bef64fc47e996a938f7d57f9e077da3 c76cf339b87975ae5b2c06d2d774d5667d25a12a git Not specified
CNA Linux Linux affected 4c8ff7095bef64fc47e996a938f7d57f9e077da3 2c97dcb6147c8f7f25c629b93be1e69617de5d4a git Not specified
CNA Linux Linux affected 4c8ff7095bef64fc47e996a938f7d57f9e077da3 39d4ee19c1e7d753dd655aebee632271b171f43a git Not specified
CNA Linux Linux affected 5.6 Not specified
CNA Linux Linux unaffected 5.6 semver Not specified
CNA Linux Linux unaffected 6.1.175 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.136 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.84 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.25 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.2 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/2c97dcb6147c8f7f25c629b93be1e69617de5d4a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/57bc678f36ac03281e877c6b84877b43f964143f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/39d4ee19c1e7d753dd655aebee632271b171f43a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/ef57cd3329b40c739b9a2e1a8a21ecc4171c6280 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/c76cf339b87975ae5b2c06d2d774d5667d25a12a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/f5154cf3ce1c8193f0c1891d3769f62740cfe6fe 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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