{"id":"CVE-2026-98789","state":"PUBLISHED","title":"bpf: Fix objects stuck in free_by_rcu_ttrace","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix objects stuck in free_by_rcu_ttrace\n\ndo_call_rcu_ttrace() returns early when call_rcu_ttrace_in_progress is set\nand leaves the objects in free_by_rcu_ttrace. __free_rcu() frees\nwaiting_for_gp_ttrace only and clears the flag. Hence the objects that\nfree_bulk() or __free_by_rcu() added while RCU tasks trace GP was in flight\nstay in free_by_rcu_ttrace until free_bulk() or alloc_bulk() is called for\nthe same bpf_mem_cache again, which may never happen. The number of such\nobjects is not bounded.\n\nTurn call_rcu_ttrace_in_progress into three states:\n0 - idle\n1 - __free_rcu() is queued\n2 - __free_rcu() is queued and free_by_rcu_ttrace got more objects since\n\ndo_call_rcu_ttrace() sets 2. __free_rcu() does cmpxchg(1 -> 0) and starts\nthe next GP when it fails. It cannot clear the flag first and check\nfree_by_rcu_ttrace later, since bpf_mem_alloc_destroy() frees bpf_mem_cache\nwithout waiting for RCU callbacks when the flag is zero.\n\nNow __free_rcu() queues itself, so the one that didn't see 'draining' may\ndo call_rcu_tasks_trace() after rcu_barrier_tasks_trace() in\nfree_mem_alloc(). Queue it under rcu_read_lock() and do synchronize_rcu()\nbefore the barriers. Calling rcu_barrier_tasks_trace() twice works too, but\ncreating and destroying hash maps in a loop on many cpus slows down to one\nfree_mem_alloc() per GP and kworkers pile up.","publishedAt":"2026-10-18T15:48:25.665Z","updatedAt":"2026-10-19T09:25:42.177Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"8d5a8011b35d387c490a5c977b1d9eb4798aa071","status":"affected","lessThan":"33d0a5d2fee06a51f2f056dd901296515912e954","versionType":"git"},{"version":"8d5a8011b35d387c490a5c977b1d9eb4798aa071","status":"affected","lessThan":"fbd97dd1d3ce32d32fb7be86acc3fdb7c04fa043","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/memalloc.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.1","versionType":"semver"},{"version":"7.2.10","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/memalloc.c"]}],"references":["https://git.kernel.org/stable/c/33d0a5d2fee06a51f2f056dd901296515912e954","https://git.kernel.org/stable/c/fbd97dd1d3ce32d32fb7be86acc3fdb7c04fa043"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98789.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98789","state":"PUBLISHED","datePublished":"2026-10-18T15:48:25.665Z","dateUpdated":"2026-10-19T09:25:42.177Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.370Z"},"containers":{"cna":{"title":"bpf: Fix objects stuck in free_by_rcu_ttrace","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix objects stuck in free_by_rcu_ttrace\n\ndo_call_rcu_ttrace() returns early when call_rcu_ttrace_in_progress is set\nand leaves the objects in free_by_rcu_ttrace. __free_rcu() frees\nwaiting_for_gp_ttrace only and clears the flag. Hence the objects that\nfree_bulk() or __free_by_rcu() added while RCU tasks trace GP was in flight\nstay in free_by_rcu_ttrace until free_bulk() or alloc_bulk() is called for\nthe same bpf_mem_cache again, which may never happen. The number of such\nobjects is not bounded.\n\nTurn call_rcu_ttrace_in_progress into three states:\n0 - idle\n1 - __free_rcu() is queued\n2 - __free_rcu() is queued and free_by_rcu_ttrace got more objects since\n\ndo_call_rcu_ttrace() sets 2. __free_rcu() does cmpxchg(1 -> 0) and starts\nthe next GP when it fails. It cannot clear the flag first and check\nfree_by_rcu_ttrace later, since bpf_mem_alloc_destroy() frees bpf_mem_cache\nwithout waiting for RCU callbacks when the flag is zero.\n\nNow __free_rcu() queues itself, so the one that didn't see 'draining' may\ndo call_rcu_tasks_trace() after rcu_barrier_tasks_trace() in\nfree_mem_alloc(). Queue it under rcu_read_lock() and do synchronize_rcu()\nbefore the barriers. Calling rcu_barrier_tasks_trace() twice works too, but\ncreating and destroying hash maps in a loop on many cpus slows down to one\nfree_mem_alloc() per GP and kworkers pile up."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"8d5a8011b35d387c490a5c977b1d9eb4798aa071","status":"affected","lessThan":"33d0a5d2fee06a51f2f056dd901296515912e954","versionType":"git"},{"version":"8d5a8011b35d387c490a5c977b1d9eb4798aa071","status":"affected","lessThan":"fbd97dd1d3ce32d32fb7be86acc3fdb7c04fa043","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/memalloc.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.1","versionType":"semver"},{"version":"7.2.10","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/memalloc.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/33d0a5d2fee06a51f2f056dd901296515912e954"},{"url":"https://git.kernel.org/stable/c/fbd97dd1d3ce32d32fb7be86acc3fdb7c04fa043"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:25:42.177Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"7.2.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}