In the Linux kernel, the following vulnerability has been resolved: bpf: Fix NMI/tracepoint re-entry deadlock on lru locks NMI and tracepoint BPF programs can re-enter the per-CPU or global LRU lock that bpflrupopfree()/pushfree() already hold on the same CPU, AA-deadlocking. Lockdep reports "inconsistent {INITIAL USE} -> {IN-NMI}" on &l->lock (syzbot c69a0a2c816716f1e0d5) and "possible recursive locking detected" on &locl->lock (syzbot 18b26edb69b2e19f3b33). Prior trylock and rqspinlock based fixes (see links) were nacked because compromised on reliability. This patch converts every LRU lock site to rqspinlockt and adds a recovery path for some failure windows to avoid node leaks. Failure recovery: - *popfree top-level: return NULL; prealloclrupop() already treats that as no-free-element (-ENOMEM). - Cross-CPU steal: skip the victim's locked locl, try next CPU. - Post-steal local lock fail: publish stolen node to lockless per-CPU freellist; next pop on this CPU picks it up. - pushfree fail: mark node pendingfree=1. __locallistflush(), __locallistpoppending() reclaim the node from pendinglist. __bpflrulistshrinkinactive() reclaims the node from inactive list. Nodes from active list are reclaimed by __bpflrulist_shrink() or after __bpflrulistrotateactive() demotes it to the inactive.