Description
In 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.
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
63c882a05416e18de6fb59f7dd6da48f3bbe8273 to < 27d172b60eeca5c8fd51b246f9fb959067cf102baffected63c882a05416e18de6fb59f7dd6da48f3bbe8273 to < 2f09f08d602647fc4e328fc27ecb4c3008d10338affected63c882a05416e18de6fb59f7dd6da48f3bbe8273 to < de75382d6e354b2b055df4896d12a91969f12090affected63c882a05416e18de6fb59f7dd6da48f3bbe8273 to < 343ae18e960f6c5f1d34d58a69750c62cd463228affected63c882a05416e18de6fb59f7dd6da48f3bbe8273 to < 92289e66639f62abc754c6f3bce5ead7e98e4ee2affected63c882a05416e18de6fb59f7dd6da48f3bbe8273 to < 947400af98b9e63841929d079a2c3ea0a8ba227baffected63c882a05416e18de6fb59f7dd6da48f3bbe8273 to < ac8d8b599d466a129122bded77db3d0f8b96b461affected63c882a05416e18de6fb59f7dd6da48f3bbe8273 to < e422777fdd4746de1109575c51e65038d4c5c1beaffected
Linux Linux
Default version status: affected
2.6.31affected0 to < 2.6.31unaffected5.10.270 to ≤ 5.10.*unaffected5.15.221 to ≤ 5.15.*unaffected6.1.188 to ≤ 6.1.*unaffected6.6.157 to ≤ 6.6.*unaffected6.12.110 to ≤ 6.12.*unaffected6.18.51 to ≤ 6.18.*unaffected7.2.4 to ≤ 7.2.*unaffected7.3 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/27d172b60eeca5c8fd51b246f9fb959067cf102b ↗
- https://git.kernel.org/stable/c/2f09f08d602647fc4e328fc27ecb4c3008d10338 ↗
- https://git.kernel.org/stable/c/de75382d6e354b2b055df4896d12a91969f12090 ↗
- https://git.kernel.org/stable/c/343ae18e960f6c5f1d34d58a69750c62cd463228 ↗
- https://git.kernel.org/stable/c/92289e66639f62abc754c6f3bce5ead7e98e4ee2 ↗
- https://git.kernel.org/stable/c/947400af98b9e63841929d079a2c3ea0a8ba227b ↗
- https://git.kernel.org/stable/c/ac8d8b599d466a129122bded77db3d0f8b96b461 ↗
- https://git.kernel.org/stable/c/e422777fdd4746de1109575c51e65038d4c5c1be ↗