mm/filemap: __filemap_add_folio() restore index before retrying

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-74591
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-22 16:16:31 UTC
Updated2026-08-25 06:18:34 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: mm/filemap: __filemap_add_folio() restore index before retrying In __filemap_add_folio()'s split-a-conflict loop, xas_set_order() is applied repeatedly: each application modifies xas.xa_index, rounding it down according to the split_order attempted at that stage: and if all goes as intended, it eventually (or immediately) converges on an xas_try_split() to the required folio_order, with xas.xa_index now the same as index: then xas_store() puts the new folio into the xarray there. But if a new node was needed, and GFP_NOWAIT allocation did not get one, the lock is dropped, xas_nomem() used to allocate, and sequence retried. If (that part of) the xarray is unchanged when the lock is reacquired, no problem. But what if the conflict was meanwhile resolved by another thread (perhaps even doing the same thing, inserting a folio at that same index)? Isn't there a danger of now putting our folio into the xarray at an intermediate rounded-down index? With !folio_contains() bug to follow, when CONFIG_DEBUG_VM=y is checking for that. Fix this with an xas_set_order() to restore the original xas.xa_index at the bottom of the loop, so the retry does a full re-evaluation after reacquiring the lock, and cannot reach xas_store() with the wrong index. Production was suffering from rare SIGILLs and SIGSEGVs, executable text found a page away from where it belonged, !folio_contains() bug hit when debug enabled: symptoms not seen since this patch went in.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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

EPSS: 0.004420000 probability, percentile 0.366520000 (date 2026-08-25)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

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

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 200a89c159a7a416115e6e309183c82183bf98aa 4917e3ebcab50f0265e8ca01c8567de4c4a47511 git Not specified
CNA Linux Linux affected 200a89c159a7a416115e6e309183c82183bf98aa 267ecd2eb7759c26f1a026eb0a5b231071534c9c git Not specified
CNA Linux Linux affected 200a89c159a7a416115e6e309183c82183bf98aa 86da3f7e1e609e1e8bfbab198af68467c5a015a5 git Not specified
CNA Linux Linux affected 6.15 Not specified
CNA Linux Linux unaffected 6.15 semver Not specified
CNA Linux Linux unaffected 6.18.45 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.9 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/4917e3ebcab50f0265e8ca01c8567de4c4a47511 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/86da3f7e1e609e1e8bfbab198af68467c5a015a5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/267ecd2eb7759c26f1a026eb0a5b231071534c9c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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