CVE-2026-98536 (GCVE-0-2026-98536)

Vulnerability from cvelistv5 – Published: 2026-10-18 15:18 – Updated: 2026-10-19 09:21
VLAI
Title
writeback: report a Tasks-RCU quiescent state per cgwb drain pass
Summary
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. 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.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6820 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: c22d70a162d3cc177282c4487be4d54876ca55c8 , < 863049b4018237d1590cd13b16e9fe9c0faad2c6 (git)
Affected: c22d70a162d3cc177282c4487be4d54876ca55c8 , < 42462b5bb0dec57db7f85d0f77655c737d45754d (git)
Affected: c22d70a162d3cc177282c4487be4d54876ca55c8 , < ebf1555ad2821be06f87a88ffd9a2cab8d2200e1 (git)
Affected: c22d70a162d3cc177282c4487be4d54876ca55c8 , < 4eb889649eaf65f4a5727b04ba1c017b7d05bb16 (git)
Affected: c22d70a162d3cc177282c4487be4d54876ca55c8 , < fd3bf32279df98751364b3609eb100a3e42f253b (git)
Affected: c22d70a162d3cc177282c4487be4d54876ca55c8 , < 260f586a80e7f624dd7f069898a75a904f34d373 (git)
Affected: c22d70a162d3cc177282c4487be4d54876ca55c8 , < 407a5d205179a4ab186571b0e16ec42725dc77bc (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.14
Unaffected: 0 , < 5.14 (semver)
Unaffected: 5.15.222 , ≤ 5.15.* (semver)
Unaffected: 6.1.189 , ≤ 6.1.* (semver)
Unaffected: 6.6.158 , ≤ 6.6.* (semver)
Unaffected: 6.12.112 , ≤ 6.12.* (semver)
Unaffected: 6.18.55 , ≤ 6.18.* (semver)
Unaffected: 7.2.9 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

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        }
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      "providerMetadata": {
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        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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    "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"
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      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "writeback: report a Tasks-RCU quiescent state per cgwb drain pass",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-98536.json",
      "version": "5"
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        "id": "CVE-2026-98536",
        "lastModified": "2026-10-19T10:19:09.220",
        "metrics": {},
        "published": "2026-10-18T16:17:05.357",
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        "vulnStatus": "Received"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-10-30T07:02:11+00:00",
      "cve": "CVE-2026-98536",
      "id": "CVE-2026-98536",
      "initial_release_date": "2026-10-18T00:00:00+00:00",
      "product_status:known_affected": "250",
      "product_status:known_not_affected": "29",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: writeback: report a Tasks-RCU quiescent state per cgwb drain pass",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98536.json",
      "version": "3"
    }
  }
}



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