bpf: Fix objects stuck in free_by_rcu_ttrace

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98789
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-18 16:17:32 UTC
Updated2026-10-19 10:19:42 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: bpf: Fix objects stuck in free_by_rcu_ttrace do_call_rcu_ttrace() returns early when call_rcu_ttrace_in_progress is set and leaves the objects in free_by_rcu_ttrace. __free_rcu() frees waiting_for_gp_ttrace only and clears the flag. Hence the objects that free_bulk() or __free_by_rcu() added while RCU tasks trace GP was in flight stay in free_by_rcu_ttrace until free_bulk() or alloc_bulk() is called for the same bpf_mem_cache again, which may never happen. The number of such objects is not bounded. Turn call_rcu_ttrace_in_progress into three states: 0 - idle 1 - __free_rcu() is queued 2 - __free_rcu() is queued and free_by_rcu_ttrace got more objects since do_call_rcu_ttrace() sets 2. __free_rcu() does cmpxchg(1 -> 0) and starts the next GP when it fails. It cannot clear the flag first and check free_by_rcu_ttrace later, since bpf_mem_alloc_destroy() frees bpf_mem_cache without waiting for RCU callbacks when the flag is zero. Now __free_rcu() queues itself, so the one that didn't see 'draining' may do call_rcu_tasks_trace() after rcu_barrier_tasks_trace() in free_mem_alloc(). Queue it under rcu_read_lock() and do synchronize_rcu() before the barriers. Calling rcu_barrier_tasks_trace() twice works too, but creating and destroying hash maps in a loop on many cpus slows down to one free_mem_alloc() per GP and kworkers pile up.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 8d5a8011b35d387c490a5c977b1d9eb4798aa071 33d0a5d2fee06a51f2f056dd901296515912e954 git Not specified
CNA Linux Linux affected 8d5a8011b35d387c490a5c977b1d9eb4798aa071 fbd97dd1d3ce32d32fb7be86acc3fdb7c04fa043 git Not specified
CNA Linux Linux affected 6.1 Not specified
CNA Linux Linux unaffected 6.1 semver Not specified
CNA Linux Linux unaffected 7.2.10 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/33d0a5d2fee06a51f2f056dd901296515912e954 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/fbd97dd1d3ce32d32fb7be86acc3fdb7c04fa043 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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