writeback: report a Tasks-RCU quiescent state per cgwb drain pass
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 w
CVE-2026-98536
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-98536
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"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"
}
]- Related CVEs
- CVE-2026-98536
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #38561 · Revision 1
- Added to Heist Feed
- Publisher date