CVE-2026-98536writeback: report a Tasks-RCU quiescent state per cgwb drain pass

Description

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.

Timeline

Scores

No CVSS score yet: neither the CNA, CISA nor NVD has scored this CVE. NVD status: Received.

EPSS (exploitation in 30 days)

0.21% · top 88% of all CVEs (12 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: Not scored.

Affected products

• Linux · Linux

  • affected c22d70a162d3cc177282c4487be4d54876ca55c8 – < 863049b4018237d1590cd13b16e9fe9c0faad2c6
  • affected c22d70a162d3cc177282c4487be4d54876ca55c8 – < 42462b5bb0dec57db7f85d0f77655c737d45754d
  • affected c22d70a162d3cc177282c4487be4d54876ca55c8 – < ebf1555ad2821be06f87a88ffd9a2cab8d2200e1
  • affected c22d70a162d3cc177282c4487be4d54876ca55c8 – < 4eb889649eaf65f4a5727b04ba1c017b7d05bb16
  • affected c22d70a162d3cc177282c4487be4d54876ca55c8 – < fd3bf32279df98751364b3609eb100a3e42f253b
  • affected c22d70a162d3cc177282c4487be4d54876ca55c8 – < 260f586a80e7f624dd7f069898a75a904f34d373
  • affected c22d70a162d3cc177282c4487be4d54876ca55c8 – < 407a5d205179a4ab186571b0e16ec42725dc77bc

• Linux · Linux

  • affected 5.14
  • unaffected < 5.14
  • unaffected 5.15.222 – ≤ 5.15.*
  • unaffected 6.1.189 – ≤ 6.1.*
  • unaffected 6.6.158 – ≤ 6.6.*
  • unaffected 6.12.112 – ≤ 6.12.*
  • unaffected 6.18.55 – ≤ 6.18.*
  • unaffected 7.2.9 – ≤ 7.2.*
  • unaffected 7.3 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-103581 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-98536](https://cveledger.app/badge/CVE-2026-98536.svg)](https://cveledger.app/cve/CVE-2026-98536)

Record last updated 19 Oct 2026, 09:21 UTC.