In the Linux kernel, the following vulnerability has been resolved:
cachestat: do not flush stats in recency check
syzbot detects that cachestat() is flushing stats, which can sleep, in its RCU read section (see 1). This is done in the workingset_test_recent() step (which checks if the folio's eviction is recent).
Move the stat flushing step to before the RCU read section of cachestat, and skip stat flushing during the recency check.