{"cve":"CVE-2026-98789","nvd":{"published":"2026-10-18T16:17:32.887","modified":"2026-10-19T10:19:42.963","status":"Received","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.","cvss_v4":null,"cvss_v3":null,"cwes":[],"references":["https://git.kernel.org/stable/c/33d0a5d2fee06a51f2f056dd901296515912e954","https://git.kernel.org/stable/c/fbd97dd1d3ce32d32fb7be86acc3fdb7c04fa043"],"products":[],"source":"nvd","synced_at":"2026-10-19T23:00:53.604569364+00:00"},"epss":{"cve":"CVE-2026-98789","score":0.00155,"percentile":0.04619,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}