{"api_version":"1","generated_at":"2026-10-26T07:02:35+00:00","cve":"CVE-2026-98536","urls":{"html":"https://cve.report/CVE-2026-98536","api":"https://cve.report/api/cve/CVE-2026-98536.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-98536","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-98536"},"summary":{"title":"writeback: report a Tasks-RCU quiescent state per cgwb drain pass","description":"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.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-10-18 16:17:05","updated_at":"2026-10-18 16:17:05"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/4eb889649eaf65f4a5727b04ba1c017b7d05bb16","name":"https://git.kernel.org/stable/c/4eb889649eaf65f4a5727b04ba1c017b7d05bb16","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/fd3bf32279df98751364b3609eb100a3e42f253b","name":"https://git.kernel.org/stable/c/fd3bf32279df98751364b3609eb100a3e42f253b","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/42462b5bb0dec57db7f85d0f77655c737d45754d","name":"https://git.kernel.org/stable/c/42462b5bb0dec57db7f85d0f77655c737d45754d","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/407a5d205179a4ab186571b0e16ec42725dc77bc","name":"https://git.kernel.org/stable/c/407a5d205179a4ab186571b0e16ec42725dc77bc","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/260f586a80e7f624dd7f069898a75a904f34d373","name":"https://git.kernel.org/stable/c/260f586a80e7f624dd7f069898a75a904f34d373","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ebf1555ad2821be06f87a88ffd9a2cab8d2200e1","name":"https://git.kernel.org/stable/c/ebf1555ad2821be06f87a88ffd9a2cab8d2200e1","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/863049b4018237d1590cd13b16e9fe9c0faad2c6","name":"https://git.kernel.org/stable/c/863049b4018237d1590cd13b16e9fe9c0faad2c6","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-98536","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98536","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c22d70a162d3cc177282c4487be4d54876ca55c8 863049b4018237d1590cd13b16e9fe9c0faad2c6 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c22d70a162d3cc177282c4487be4d54876ca55c8 42462b5bb0dec57db7f85d0f77655c737d45754d git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c22d70a162d3cc177282c4487be4d54876ca55c8 ebf1555ad2821be06f87a88ffd9a2cab8d2200e1 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c22d70a162d3cc177282c4487be4d54876ca55c8 4eb889649eaf65f4a5727b04ba1c017b7d05bb16 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c22d70a162d3cc177282c4487be4d54876ca55c8 fd3bf32279df98751364b3609eb100a3e42f253b git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c22d70a162d3cc177282c4487be4d54876ca55c8 260f586a80e7f624dd7f069898a75a904f34d373 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c22d70a162d3cc177282c4487be4d54876ca55c8 407a5d205179a4ab186571b0e16ec42725dc77bc git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.14","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.14 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.222 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.189 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.158 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.112 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.55 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.9 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["mm/backing-dev.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"863049b4018237d1590cd13b16e9fe9c0faad2c6","status":"affected","version":"c22d70a162d3cc177282c4487be4d54876ca55c8","versionType":"git"},{"lessThan":"42462b5bb0dec57db7f85d0f77655c737d45754d","status":"affected","version":"c22d70a162d3cc177282c4487be4d54876ca55c8","versionType":"git"},{"lessThan":"ebf1555ad2821be06f87a88ffd9a2cab8d2200e1","status":"affected","version":"c22d70a162d3cc177282c4487be4d54876ca55c8","versionType":"git"},{"lessThan":"4eb889649eaf65f4a5727b04ba1c017b7d05bb16","status":"affected","version":"c22d70a162d3cc177282c4487be4d54876ca55c8","versionType":"git"},{"lessThan":"fd3bf32279df98751364b3609eb100a3e42f253b","status":"affected","version":"c22d70a162d3cc177282c4487be4d54876ca55c8","versionType":"git"},{"lessThan":"260f586a80e7f624dd7f069898a75a904f34d373","status":"affected","version":"c22d70a162d3cc177282c4487be4d54876ca55c8","versionType":"git"},{"lessThan":"407a5d205179a4ab186571b0e16ec42725dc77bc","status":"affected","version":"c22d70a162d3cc177282c4487be4d54876ca55c8","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["mm/backing-dev.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.14"},{"lessThan":"5.14","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.222","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.189","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.158","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.112","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.55","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.9","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.15.222","versionStartIncluding":"5.14","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.189","versionStartIncluding":"5.14","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.158","versionStartIncluding":"5.14","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.112","versionStartIncluding":"5.14","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.55","versionStartIncluding":"5.14","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.9","versionStartIncluding":"5.14","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3","versionStartIncluding":"5.14","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"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."}],"providerMetadata":{"dateUpdated":"2026-10-19T09:21:19.730Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/863049b4018237d1590cd13b16e9fe9c0faad2c6"},{"url":"https://git.kernel.org/stable/c/42462b5bb0dec57db7f85d0f77655c737d45754d"},{"url":"https://git.kernel.org/stable/c/ebf1555ad2821be06f87a88ffd9a2cab8d2200e1"},{"url":"https://git.kernel.org/stable/c/4eb889649eaf65f4a5727b04ba1c017b7d05bb16"},{"url":"https://git.kernel.org/stable/c/fd3bf32279df98751364b3609eb100a3e42f253b"},{"url":"https://git.kernel.org/stable/c/260f586a80e7f624dd7f069898a75a904f34d373"},{"url":"https://git.kernel.org/stable/c/407a5d205179a4ab186571b0e16ec42725dc77bc"}],"title":"writeback: report a Tasks-RCU quiescent state per cgwb drain pass","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-98536","datePublished":"2026-10-18T15:18:04.013Z","dateReserved":"2026-09-25T10:25:14.355Z","dateUpdated":"2026-10-19T09:21:19.730Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-18 16:17:05","lastModifiedDate":"2026-10-18 16:17:05","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"98536","Ordinal":"1","Title":"writeback: report a Tasks-RCU quiescent state per cgwb drain pas","CVE":"CVE-2026-98536","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"98536","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"writeback: report a Tasks-RCU quiescent state per cgwb drain pas"}]}}}