CVE-2026-98536
In the Linux kernel, the following vulnerability has been resolved:
writeback: report a Tasks-RCU quiescent state per cgwb drain pass
cleanup_offline_cgwbs_workfn() drains a dying cgwb by calling cleanup_offline_cgwb() until it returns false, with a cond_resched() between passes. On a CONFIG_PREEMPTION kernel that cond_resched() does nothing: _cond_resched() is a plain "return 0", and under PREEMPT_DYNAMIC the full and lazy modes disable it. Since commit 7dadeaa6e851 ("sched: Further restrict the preemption modes") those are the only two models on the architectures with PREEMPT_LAZY support, arm64 and x86 among them, so the drain loop never reports a Tasks-RCU quiescent state.
Read full descriptionShow less
A worker draining a cgwb with millions of attached inodes runs for minutes. On a 6.18 arm64 host in lazy mode the cgwb worker drained one dying cgroup's writeback domain for over 11 minutes. A BPF program unlink (bpf_trampoline_unlink_prog -> bpf_trampoline_update -> unregister_ftrace_direct -> ftrace_shutdown -> synchronize_rcu_tasks()) waited on that grace period while holding the trampoline mutex, 42 tasks queued behind it in D state, and the hung task detector fired at 614 s and panicked the host. Any BPF or ftrace detach during a long drain inherits the drain's length.
Fix this by calling cond_resched_tasks_rcu_qs() so we do not stall out anybody who calls sycnrhonize_rcu_tasks(). We put this in a do { } while loop because if we have many small cgroups cleanup_offline_cgwb() will return false and we will never call cond_resched_tasks_rcu_qs(), creating the same problem.
CVSS
NVD hasn't assigned a CVSS score to this CVE (common since the April 2026 policy change).
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days
- 0.21 %
- Percentile among all scored CVEs
- 11
- Score date
- 10/20/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
Affected technologies (1)
⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.
References
Show 7 references
- https://git.kernel.org/stable/c/260f586a80e7f624dd7f069898a75a904f34d373
- https://git.kernel.org/stable/c/407a5d205179a4ab186571b0e16ec42725dc77bc
- https://git.kernel.org/stable/c/42462b5bb0dec57db7f85d0f77655c737d45754d
- https://git.kernel.org/stable/c/4eb889649eaf65f4a5727b04ba1c017b7d05bb16
- https://git.kernel.org/stable/c/863049b4018237d1590cd13b16e9fe9c0faad2c6
- https://git.kernel.org/stable/c/ebf1555ad2821be06f87a88ffd9a2cab8d2200e1
- https://git.kernel.org/stable/c/fd3bf32279df98751364b3609eb100a3e42f253b
Raw JSON (NVD)
Show
{
"id": "CVE-2026-98536",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "c22d70a162d3cc177282c4487be4d54876ca55c8",
"lessThan": "863049b4018237d1590cd13b16e9fe9c0faad2c6",
"versionType": "git"
},
{
"status": "affected",
"version": "c22d70a162d3cc177282c4487be4d54876ca55c8",
"lessThan": "42462b5bb0dec57db7f85d0f77655c737d45754d",
"versionType": "git"
},
{
"status": "affected",
"version": "c22d70a162d3cc177282c4487be4d54876ca55c8",
"lessThan": "ebf1555ad2821be06f87a88ffd9a2cab8d2200e1",
"versionType": "git"
},
{
"status": "affected",
"version": "c22d70a162d3cc177282c4487be4d54876ca55c8",
"lessThan": "4eb889649eaf65f4a5727b04ba1c017b7d05bb16",
"versionType": "git"
},
{
"status": "affected",
"version": "c22d70a162d3cc177282c4487be4d54876ca55c8",
"lessThan": "fd3bf32279df98751364b3609eb100a3e42f253b",
"versionType": "git"
},
{
"status": "affected",
"version": "c22d70a162d3cc177282c4487be4d54876ca55c8",
"lessThan": "260f586a80e7f624dd7f069898a75a904f34d373",
"versionType": "git"
},
{
"status": "affected",
"version": "c22d70a162d3cc177282c4487be4d54876ca55c8",
"lessThan": "407a5d205179a4ab186571b0e16ec42725dc77bc",
"versionType": "git"
}
],
"programFiles": [
"mm/backing-dev.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "5.14"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "5.14",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.15.222",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.189",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.158",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.112",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.55",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.9",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"mm/backing-dev.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-10-18T16:17:05.357",
"references": [
{
"url": "https://git.kernel.org/stable/c/260f586a80e7f624dd7f069898a75a904f34d373",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/407a5d205179a4ab186571b0e16ec42725dc77bc",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/42462b5bb0dec57db7f85d0f77655c737d45754d",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/4eb889649eaf65f4a5727b04ba1c017b7d05bb16",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/863049b4018237d1590cd13b16e9fe9c0faad2c6",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/ebf1555ad2821be06f87a88ffd9a2cab8d2200e1",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/fd3bf32279df98751364b3609eb100a3e42f253b",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"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."
}
],
"lastModified": "2026-10-19T10:19:09.220",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}