ext4: fix use-after-free in update_super_work when racing with umount
In the Linux kernel, the following vulnerability has been resolved: ext4: fix use-after-free in update_super_work when racing with umount Commit b98535d09179 ("ext4: fix bug_on in start_this_handle during umount filesystem") moved ext4_unregister_sysfs() before flushing s_sb_upd_work to prevent new error work from being queued via /proc/fs/ext4/xx/mb_groups reads during unmount. However, this introduced a use-after-free because update_super_work calls ext4_notify_error_sysfs() -> sysfs_notify() which accesses the kobject's kernfs_node after it has been freed by kobject_del() in ext4_unregister_sysfs(): update_super_work ext4_put_super ----------------- -------------- ext4_unregister_sysfs(sb) kobject_del(&sbi->s_kobj) __kobject_del() sysfs_remove_dir() kobj->sd = NULL sysfs_put(sd) kernfs_put() // RCU free ext4_notify_error_sysfs(sbi) sysfs_notify(&sbi->s_kobj) kn = kobj->sd // stale pointer kernfs_get(kn) // UAF on freed kernfs_node ext4_journal_destroy() flush_work(&sbi->s_sb_upd_work) Instead of reordering the teardown sequence, fix this by making ext4_notify_error_sysfs() detect that sysfs has already been torn down by checking s_kobj.state_in_sysfs, and skipping the sysfs_notify() call in that case. A dedicated mutex (s_error_notify_mutex) serializes ext4_notify_error_sysfs() against kobject_del() in ext4_unregister_sysfs() to prevent TOCTOU races where the kobject could be deleted between the state_in_sysfs check and the sysfs_notify() call.
CVE-2026-31446
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-2026-31446
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": "52c3a04f9ec2a16a4204d6274db338cb8d5b2d74",
"lessThan": "c8fe17a1b308c3d8c703ebfb049b325f844342c3",
"versionType": "git"
},
{
"status": "affected",
"version": "b98535d091795a79336f520b0708457aacf55c67",
"lessThan": "c4d829737329f2290dd41e290b7d75effdb2a7ff",
"versionType": "git"
},
{
"status": "affected",
"version": "b98535d091795a79336f520b0708457aacf55c67",
"lessThan": "9449f99ba04f5dd1c8423ad8a90b3651d7240d1d",
"versionType": "git"
},
{
"status": "affected",
"version": "b98535d091795a79336f520b0708457aacf55c67",
"lessThan": "034053378dd81837fd6c7a43b37ee2e58d4f0b4e",
"versionType": "git"
},
{
"status": "affected",
"version": "b98535d091795a79336f520b0708457aacf55c67",
"lessThan": "c97e282f7bfd0c3554c63d289964a5ca6a1d2ffe",
"versionType": "git"
},
{
"status": "affected",
"version": "b98535d091795a79336f520b0708457aacf55c67",
"lessThan": "08b10e6f37fc533a759e9833af0692242e8b3f93",
"versionType": "git"
},
{
"status": "affected",
"version": "b98535d091795a79336f520b0708457aacf55c67",
"lessThan": "d15e4b0a418537aafa56b2cb80d44add83e83697",
"versionType": "git"
},
{
"status": "affected",
"version": "585ef03c9e79672781f954daae730dfe24bf3a46",
"versionType": "git"
},
{
"status": "affected",
"version": "afe490e48d47df1b3f64012835c1bc2f075a8c8b",
"versionType": "git"
},
{
"status": "affected",
"version": "5.15.38",
"lessThan": "5.15.203",
"versionType": "semver"
},
{
"status": "affected",
"version": "5.10.114",
"lessThan": "5.11",
"versionType": "semver"
},
{
"status": "affected",
"version": "5.17.6",
"lessThan": "5.18",
"versionType": "semver"
}
],
"programFiles": [
"fs/ext4/ext4.h",
"fs/ext4/super.c",
"fs/ext4/sysfs.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "5.18"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "5.18",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.15.203",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.168",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.131",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.80",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.21",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "6.19.11",
"versionType": "semver",
"lessThanOrEqual": "6.19.*"
},
{
"status": "unaffected",
"version": "7.0",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/ext4/ext4.h",
"fs/ext4/super.c",
"fs/ext4/sysfs.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-31446
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #39877 · Revision 1
- Added to Heist Feed
- Publisher date