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CVE PROGRAM SOURCE RECORDUnscored

CVE-2026-31702

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

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In 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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 4c8ff7095bef64fc47e996a938f7d57f9e077da3 to < 57bc678f36ac03281e877c6b84877b43f964143faffected
  • 4c8ff7095bef64fc47e996a938f7d57f9e077da3 to < ef57cd3329b40c739b9a2e1a8a21ecc4171c6280affected
  • 4c8ff7095bef64fc47e996a938f7d57f9e077da3 to < f5154cf3ce1c8193f0c1891d3769f62740cfe6feaffected
  • 4c8ff7095bef64fc47e996a938f7d57f9e077da3 to < c76cf339b87975ae5b2c06d2d774d5667d25a12aaffected
  • 4c8ff7095bef64fc47e996a938f7d57f9e077da3 to < 2c97dcb6147c8f7f25c629b93be1e69617de5d4aaffected
  • 4c8ff7095bef64fc47e996a938f7d57f9e077da3 to < 39d4ee19c1e7d753dd655aebee632271b171f43aaffected

Linux Linux

Default version status: affected

  • 5.6affected
  • 0 to < 5.6unaffected
  • 6.1.175 to ≤ 6.1.*unaffected
  • 6.6.136 to ≤ 6.6.*unaffected
  • 6.12.84 to ≤ 6.12.*unaffected
  • 6.18.25 to ≤ 6.18.*unaffected
  • 7.0.2 to ≤ 7.0.*unaffected
  • 7.1 to ≤ *unaffected

References