{"schema":"threatline.record/2","record":{"id":"CVE-2026-98536","aliases":[],"summary":"writeback: report a Tasks-RCU quiescent state per cgwb drain pass","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nwriteback: report a Tasks-RCU quiescent state per cgwb drain pass\n\ncleanup_offline_cgwbs_workfn() drains a dying cgwb by calling\ncleanup_offline_cgwb() until it returns false, with a cond_resched()\nbetween passes.  On a CONFIG_PREEMPTION kernel that cond_resched() does\nnothing: _cond_resched() is a plain \"return 0\", and under PREEMPT_DYNAMIC\nthe full and lazy modes disable it.  Since commit 7dadeaa6e851 (\"sched:\nFurther restrict the preemption modes\") those are the only two models on\nthe architectures with PREEMPT_LAZY support, arm64 and x86 among them, so\nthe drain loop never reports a Tasks-RCU quiescent state.\n\nA worker draining a cgwb with millions of attached inodes runs for\nminutes.  On a 6.18 arm64 host in lazy mode the cgwb worker drained one\ndying cgroup's writeback domain for over 11 minutes.  A BPF program unlink\n(bpf_trampoline_unlink_prog -> bpf_trampoline_update ->\nunregister_ftrace_direct -> ftrace_shutdown -> synchronize_rcu_tasks())\nwaited on that grace period while holding the trampoline mutex, 42 tasks\nqueued behind it in D state, and the hung task detector fired at 614 s and\npanicked the host.  Any BPF or ftrace detach during a long drain inherits\nthe drain's length.\n\nFix this by calling cond_resched_tasks_rcu_qs() so we do not stall out\nanybody who calls sycnrhonize_rcu_tasks().  We put this in a do { } while\nloop because if we have many small cgroups cleanup_offline_cgwb() will\nreturn false and we will never call cond_resched_tasks_rcu_qs(), creating\nthe same problem.","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98536","source_modified_at":"2026-10-19T09:21:19.730Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","lessThan":"863049b4018237d1590cd13b16e9fe9c0faad2c6","status":"affected","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","lessThan":"42462b5bb0dec57db7f85d0f77655c737d45754d","status":"affected","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","lessThan":"ebf1555ad2821be06f87a88ffd9a2cab8d2200e1","status":"affected","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","lessThan":"4eb889649eaf65f4a5727b04ba1c017b7d05bb16","status":"affected","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","lessThan":"fd3bf32279df98751364b3609eb100a3e42f253b","status":"affected","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","lessThan":"260f586a80e7f624dd7f069898a75a904f34d373","status":"affected","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","lessThan":"407a5d205179a4ab186571b0e16ec42725dc77bc","status":"affected","versionType":"git"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98536","source_modified_at":"2026-10-19T09:21:19.730Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"5.14","status":"affected"},{"version":"0","lessThan":"5.14","status":"unaffected","versionType":"semver"},{"version":"5.15.222","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.189","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.158","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.112","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.55","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.9","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-2026-98536","source_modified_at":"2026-10-19T09:21:19.730Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"863049b4018237d1590cd13b16e9fe9c0faad2c6","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98536","source_modified_at":"2026-10-19T09:21:19.730Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"42462b5bb0dec57db7f85d0f77655c737d45754d","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98536","source_modified_at":"2026-10-19T09:21:19.730Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"4eb889649eaf65f4a5727b04ba1c017b7d05bb16","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98536","source_modified_at":"2026-10-19T09:21:19.730Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"260f586a80e7f624dd7f069898a75a904f34d373","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98536","source_modified_at":"2026-10-19T09:21:19.730Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"407a5d205179a4ab186571b0e16ec42725dc77bc","basis":"first unaffected version stated in the CVE record"}],"cvss":null,"severity":null,"kev":{"listed":false},"epss":{"probability":0.00215,"percentile":0.11253,"score_date":"2026-10-23"},"published_at":"2026-10-18T15:18:04.013Z","modified_at":"2026-10-19T09:21:19.730Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-98536","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-19T09:21:19.730Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-98536","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/863049b4018237d1590cd13b16e9fe9c0faad2c6"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/42462b5bb0dec57db7f85d0f77655c737d45754d"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/ebf1555ad2821be06f87a88ffd9a2cab8d2200e1"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/4eb889649eaf65f4a5727b04ba1c017b7d05bb16"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/fd3bf32279df98751364b3609eb100a3e42f253b"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/260f586a80e7f624dd7f069898a75a904f34d373"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/407a5d205179a4ab186571b0e16ec42725dc77bc"}],"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":"2026-10-19T09:21:19.730Z","content_hash":"e670ddadc2d32df1e965ab689fe6173ea45663f81420b940b6250ba138d1b9d2"}}