CVE-2026-31702 (GCVE-0-2026-31702)

Vulnerability from cvelistv5 – Published: 2026-05-01 13:56 – Updated: 2026-06-14 17:43
VLAI
Title
f2fs: fix use-after-free of sbi in f2fs_compress_write_end_io()
Summary
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.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 4c8ff7095bef64fc47e996a938f7d57f9e077da3 , < 57bc678f36ac03281e877c6b84877b43f964143f (git)
Affected: 4c8ff7095bef64fc47e996a938f7d57f9e077da3 , < ef57cd3329b40c739b9a2e1a8a21ecc4171c6280 (git)
Affected: 4c8ff7095bef64fc47e996a938f7d57f9e077da3 , < f5154cf3ce1c8193f0c1891d3769f62740cfe6fe (git)
Affected: 4c8ff7095bef64fc47e996a938f7d57f9e077da3 , < c76cf339b87975ae5b2c06d2d774d5667d25a12a (git)
Affected: 4c8ff7095bef64fc47e996a938f7d57f9e077da3 , < 2c97dcb6147c8f7f25c629b93be1e69617de5d4a (git)
Affected: 4c8ff7095bef64fc47e996a938f7d57f9e077da3 , < 39d4ee19c1e7d753dd655aebee632271b171f43a (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.6
Unaffected: 0 , < 5.6 (semver)
Unaffected: 6.1.175 , ≤ 6.1.* (semver)
Unaffected: 6.6.136 , ≤ 6.6.* (semver)
Unaffected: 6.12.84 , ≤ 6.12.* (semver)
Unaffected: 6.18.25 , ≤ 6.18.* (semver)
Unaffected: 7.0.2 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: f2fs: fix use-after-free of sbi in f2fs_compress_write_end_io()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31702.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-06-15T01:26:58Z",
      "cve": "CVE-2026-31702",
      "id": "CVE-2026-31702",
      "initial_release_date": "2026-05-02T01:25:30Z",
      "product_status:known_not_affected": "289",
      "product_status:recommended": "4",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-31702",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-31702.json",
      "version": "6"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.