bpf: Fix NMI/tracepoint re-entry deadlock on lru locks

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Summary

CVECVE-2026-74337
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-15 06:22:34 UTC
Updated2026-08-15 06:22:34 UTC
DescriptionIn 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 bpf_lru_pop_free()/push_free() 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 &loc_l->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 rqspinlock_t and adds a recovery path for some failure windows to avoid node leaks. Failure recovery: - *_pop_free top-level: return NULL; prealloc_lru_pop() already treats that as no-free-element (-ENOMEM). - Cross-CPU steal: skip the victim's locked loc_l, try next CPU. - Post-steal local lock fail: publish stolen node to lockless per-CPU free_llist; next pop on this CPU picks it up. - push_free fail: mark node pending_free=1. __local_list_flush(), __local_list_pop_pending() reclaim the node from pending_list. __bpf_lru_list_shrink_inactive() reclaims the node from inactive list. Nodes from active list are reclaimed by __bpf_lru_list_shrink() or after __bpf_lru_list_rotate_active() demotes it to the inactive.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 3a08c2fd763450a927d1130de078d6f9e74944fb 8b0510cc3a4a000d4ed1a56cd96231f3d3ba94c5 git Not specified
CNA Linux Linux affected 3a08c2fd763450a927d1130de078d6f9e74944fb 440a2fdbb40608d55a7b11f2be53592a3785131d git Not specified
CNA Linux Linux affected 3a08c2fd763450a927d1130de078d6f9e74944fb 89edbdfc5d0308cef57b71359331de5c4ddbf763 git Not specified
CNA Linux Linux affected 4.10 Not specified
CNA Linux Linux unaffected 4.10 semver Not specified
CNA Linux Linux unaffected 6.18.40 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.5 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/89edbdfc5d0308cef57b71359331de5c4ddbf763 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/440a2fdbb40608d55a7b11f2be53592a3785131d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/8b0510cc3a4a000d4ed1a56cd96231f3d3ba94c5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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