fsnotify: Fix stale object mask after concurrent mark updates

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-89595
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-11 20:19:44 UTC
Updated2026-09-11 20:19:44 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: fsnotify: Fix stale object mask after concurrent mark updates When a mark gets a new event bit, fanotify and inotify may avoid recalculating the object mask if the cached aggregate already contains that bit. This is racy with a recalculation triggered by a concurrent update to another mark on the same connector. The concurrent scan can read the mark before the new bit is added, while the updater reads the old aggregate before that scan publishes its result. The updater then skips recalculation and the scan publishes a mask without the bit, leaving the object mask stale after both updates complete. This can be reproduced with two fanotify groups watching the same inode: one thread removes FAN_MODIFY from one existing mark while another thread adds FAN_MODIFY to the other mark. After both fanotify_mark() calls return, writes can fail to produce FAN_MODIFY for the group whose mark now contains the bit. This was reproduced on an unmodified v6.12.95 kernel. The equivalent inotify interleaving loses IN_MODIFY events. For normal fanotify additions, recalculate whenever the raw mark mask changes. The normal mask is not cleared asynchronously, so an unchanged addition cannot introduce missing interest. Always recalculate ignore-mask updates because FS_MODIFY handling may clear the ignore mask without taking mark->lock, making snapshot comparisons unreliable. Always recalculate after updating an existing inotify watch. Its replace path temporarily sets mark->mask to zero, so a concurrent scan can observe zero even when the old and final masks are equal. Assigning the replacement mask directly would avoid the transient zero, but existing-watch updates are infrequent, so unconditional recalculation is simpler.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 63c882a05416e18de6fb59f7dd6da48f3bbe8273 947400af98b9e63841929d079a2c3ea0a8ba227b git Not specified
CNA Linux Linux affected 63c882a05416e18de6fb59f7dd6da48f3bbe8273 ac8d8b599d466a129122bded77db3d0f8b96b461 git Not specified
CNA Linux Linux affected 63c882a05416e18de6fb59f7dd6da48f3bbe8273 e422777fdd4746de1109575c51e65038d4c5c1be git Not specified
CNA Linux Linux affected 2.6.31 Not specified
CNA Linux Linux unaffected 2.6.31 semver Not specified
CNA Linux Linux unaffected 6.18.51 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.4 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/ac8d8b599d466a129122bded77db3d0f8b96b461 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/947400af98b9e63841929d079a2c3ea0a8ba227b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e422777fdd4746de1109575c51e65038d4c5c1be 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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