bpf: Fix infinite loop in pcpu_freelist push with one possible CPU

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Summary

CVECVE-2026-89991
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-16 11:17:10 UTC
Updated2026-09-16 11:17:10 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: bpf: Fix infinite loop in pcpu_freelist push with one possible CPU __pcpu_freelist_push() can loop forever when only one CPU is possible and an NMI re-enters pcpu_freelist_push() while the interrupted context holds that CPU's freelist lock. After the current-CPU fast path fails, the fallback loop walks cpu_possible_mask while skipping the current CPU. With CONFIG_SMP=n, or when an SMP kernel is limited to one possible CPU with nr_cpus=1 or possible_cpus=1, there are no other possible CPUs to examine. The loop therefore makes no lock acquisition attempt and can never make progress. The following stack was observed on a UP system: NMI context: pcpu_freelist_push free_htab_elem htab_map_delete_elem [perf-event BPF program] __perf_event_overflow perf_event_nmi_handler exc_nmi Interrupted context: __pcpu_freelist_push pcpu_freelist_push free_htab_elem htab_map_delete_elem [raw_tp/sys_enter BPF program] __bpf_trace_sys_enter do_syscall_64 raw_res_spin_lock() detects the same-CPU recursive acquisition and returns -EDEADLK, but the subsequent fallback loop has no candidate head on a system with one possible CPU. Restore the extra fallback head that existed before the rqspinlock conversion. Keep the current-CPU fast path, then try the other possible CPUs and finally the extra head. The additional head lets a push, which cannot fail without losing a preallocated element, make progress when the only per-CPU head is held by the interrupted context. Also check the extra head from the pop path so that nodes placed there can be reused.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected f2ac0e5d1c4dcc55d6510dcaefb8f45661a9a1fb a24a146ae2cb5d9faeea96d10010fcb6579abe1f git Not specified
CNA Linux Linux affected f2ac0e5d1c4dcc55d6510dcaefb8f45661a9a1fb a5b5e62baceff9e252c6535cf42a027d04f226cf git Not specified
CNA Linux Linux affected f2ac0e5d1c4dcc55d6510dcaefb8f45661a9a1fb efebf6496685c93150df5bb0794363ae70c5f58a git Not specified
CNA Linux Linux affected 6.15 Not specified
CNA Linux Linux unaffected 6.15 semver Not specified
CNA Linux Linux unaffected 6.18.51 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.5 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/a5b5e62baceff9e252c6535cf42a027d04f226cf 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a24a146ae2cb5d9faeea96d10010fcb6579abe1f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/efebf6496685c93150df5bb0794363ae70c5f58a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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