{"schema":"threatline.record/2","record":{"id":"CVE-2026-98861","aliases":[],"summary":"fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nfprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching()\n\nunregister_fprobe() and unregister_fprobe_async() (used by BPF\nkprobe-multi) rely on standard RCU grace periods (synchronize_rcu()\nand call_rcu()) to wait until in-flight fprobe handlers complete before\nfreeing the fprobe.\n\nHowever, if an fprobe handler executes while RCU is not watching (such\nas in the idle loop or nohz_full extended quiescent states), standard\nRCU does not track preemption-disabled sections. Consequently,\nsynchronize_rcu() does not wait for those executions, which can lead\nto a use-after-free if the fprobe is freed immediately after\nunregistration. Ensure handlers exit early when !rcu_is_watching().\n\nFurthermore, fprobe_fgraph_entry() and fprobe_ftrace_entry() previously\nused guard(rcu)() and rcu_read_lock(), which invoke lockdep on every\nhit under CONFIG_PROVE_LOCKING. This adds overhead and can cause lockdep\nrecursion if probed functions interact with lockdep.\n\nSince rhltable_lookup() and rhl_for_each_entry_rcu() use\nrcu_dereference_all_check() (which checks rcu_read_lock_any_held()),\nholding preemption disabled via rcu_read_lock_sched_notrace() is fully\nvalid and sufficient so long as rcu_is_watching() is true.\n\nDefine and use guard(rcu_sched_notrace)() across fprobe_ftrace_entry(),\nfprobe_fgraph_entry(), and fprobe_return(). This eliminates fast-path\nrcu_read_lock() and lockdep overhead while guaranteeing safe grace\nperiod synchronization.","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98861","source_modified_at":"2026-10-19T09:26:55.805Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"56b4cfcf1518245493c60fd39c56978f508f1816","lessThan":"a85d0f00671b4d4527317c10ba018680f7d8d673","status":"affected","versionType":"git"},{"version":"657b594b2084b39a4bc6d8493aa2140cb00cea49","lessThan":"dd4a0d4993633b45470abf6da4ea0ca563402245","status":"affected","versionType":"git"},{"version":"657b594b2084b39a4bc6d8493aa2140cb00cea49","lessThan":"e0a6249190402a28f1e2925a81acf573157d55ef","status":"affected","versionType":"git"},{"version":"a4f6a9005ed6cfd360ef2520430927f05f92ffb0","status":"affected","versionType":"git"},{"version":"6.18.34","lessThan":"6.18.56","status":"affected","versionType":"semver"},{"version":"7.0.11","lessThan":"7.1","status":"affected","versionType":"semver"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98861","source_modified_at":"2026-10-19T09:26:55.805Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"7.1","status":"affected"},{"version":"0","lessThan":"7.1","status":"unaffected","versionType":"semver"},{"version":"6.18.56","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.10","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}],"defaultStatus":"affected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98861","source_modified_at":"2026-10-19T09:26:55.805Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"6.18.56","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98861","source_modified_at":"2026-10-19T09:26:55.805Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"7.1","basis":"first unaffected version stated in the CVE record"}],"cvss":null,"severity":null,"kev":{"listed":false},"epss":{"probability":0.00167,"percentile":0.0563,"score_date":"2026-10-23"},"published_at":"2026-10-18T15:51:22.271Z","modified_at":"2026-10-19T09:26:55.805Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-98861","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-19T09:26:55.805Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-98861","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://git.kernel.org/stable/c/a85d0f00671b4d4527317c10ba018680f7d8d673"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/dd4a0d4993633b45470abf6da4ea0ca563402245"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/e0a6249190402a28f1e2925a81acf573157d55ef"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-19T09:26:55.805Z","content_hash":"c7234e3d23e845c77e33f81da038d2fd0bf8c358a0c5734ef4440a4540e9636e"}}