CVE-2026-89566jbd2: check need_resched() when skipping busy checkpoint buffers

Official description

In the Linux kernel, the following vulnerability has been resolved: jbd2: check need_resched() when skipping busy checkpoint buffers journal_shrink_one_cp_list() skips busy checkpoint buffers when called with JBD2_SHRINK_BUSY_SKIP. The continue statement on this path also skips the need_resched() check at the end of the loop body. Consequently, when a checkpoint list contains mostly busy buffers, the shrinker can walk the entire list while holding journal->j_list_lock, even when a reschedule has been requested. Large checkpoint lists under memory pressure can therefore cause long lock hold times and leave other CPUs spinning on j_list_lock, resulting in soft lockups or RCU stalls. Route the busy-buffer path through the need_resched() check so that the shrinker can release j_list_lock and reschedule promptly, restoring parity with the clean-buffer path, which already checks need_resched(). This does not change which checkpoint buffers are eligible for removal.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/dc7ece0b827fe3b748db685fb85cd2fc3710c3f9
• https://git.kernel.org/stable/c/f83c23286e54180cdc83a36463a60003534cc290
• https://git.kernel.org/stable/c/f9182a85991a0ad5cd2940df6db75f40ad90028c
• https://git.kernel.org/stable/c/595cac7f1b32d009b97f83dd2b2d6a1a445e9bb4
• https://git.kernel.org/stable/c/f213e12ff5c9590b1034ae8da0e6d09665c772d0