Linux Kernel Daily: Race Condition Fixes and Minor Updates

Transcript

Good morning, this is Linux Kernel Daily for June 2nd, 2026.

Today's activity highlights the ongoing work to eliminate race conditions in kernel subsystems, with a particularly important fix in the device mapper cache policy.

The primary focus is a race condition fix in the S-M-Q cache policy code. Guangshuo Li identified and resolved a check-then-act race where two concurrent invalidators could both observe an entry as allocated before either acquired the necessary lock. This created a window where the second invalidator could operate on stale data, potentially corrupting S-M-Q queues or hash tables, or triggering allocation errors when the same entry gets freed twice. The fix moves the allocation check under the invalidation lock, ensuring the predicate and destructive operations are properly serialized. This addresses a flaw in an earlier locking fix from commit 2d1f7b6.

The second theme involves routine maintenance in the auxiliary display subsystem. Andy Shevchenko's updates include fixing a potential out-of-bounds read in the line display library when handling zero-length message stores, along with miscellaneous refactoring. Linus noted these changes are small enough to merge immediately rather than delay until the next release cycle.

Both fixes address memory safety issues - the device mapper fix prevents data structure corruption under concurrent access, while the auxiliary display fix prevents buffer overruns. These represent the kind of defensive programming that's essential for kernel stability.

Looking ahead, the device mapper fix should eliminate cache corruption scenarios in production systems using S-M-Q policy, while the auxiliary display changes improve robustness for systems using character displays. Both changes target edge cases that could cause system instability.

That's your Linux Kernel Daily briefing.