futex: Clear stale exiting pointer in futex_lock_pi() retry path
In the Linux kernel, the following vulnerability has been resolved: futex: Clear stale exiting pointer in futex_lock_pi() retry path Fuzzying/stressing futexes triggered: WARNING: kernel/futex/core.c:825 at wait_for_owner_exiting+0x7a/0x80, CPU#11: futex_lock_pi_s/524 When futex_lock_pi_atomic() sees the owner is exiting, it returns -EBUSY and stores a refcounted task pointer in 'exiting'. After wait_for_owner_exiting() consumes that reference, the local pointer is never reset to nil. Upon a retry, if futex_lock_pi_atomic() returns a different error, the bogus pointer is passed to wait_for_owner_exiting(). CPU0 CPU1 CPU2 futex_lock_pi(uaddr) // acquires the PI futex exit() futex_cleanup_begin() futex_state = EXITING; futex_lock_pi(uaddr) futex_lock_pi_atomic() attach_to_pi_owner() // observes EXITING *exiting = owner; // takes ref return -EBUSY wait_for_owner_exiting(-EBUSY, owner) put_task_struct(); // drops ref // exiting still points to owner goto retry; futex_lock_pi_atomic() lock_pi_update_atomic() cmpxchg(uaddr) *uaddr ^= WAITERS // whatever // value changed return -EAGAIN; wait_for_owner_exiting(-EAGAIN, exiting) // stale WARN_ON_ONCE(exiting) Fix this by resetting upon retry, essentially aligning it with requeue_pi.
CVE-2026-31555
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-2026-31555
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": "3ef240eaff36b8119ac9e2ea17cbf41179c930ba",
"lessThan": "33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa",
"versionType": "git"
},
{
"status": "affected",
"version": "3ef240eaff36b8119ac9e2ea17cbf41179c930ba",
"lessThan": "e7824ec168d2ac883a213cd1f4d6cc0816002a85",
"versionType": "git"
},
{
"status": "affected",
"version": "3ef240eaff36b8119ac9e2ea17cbf41179c930ba",
"lessThan": "5e8e06bf8909e79b4acd950cf578cfc2f10bbefa",
"versionType": "git"
},
{
"status": "affected",
"version": "3ef240eaff36b8119ac9e2ea17cbf41179c930ba",
"lessThan": "de7c0c04ad868f2cee6671b11c0a6d20421af1da",
"versionType": "git"
},
{
"status": "affected",
"version": "3ef240eaff36b8119ac9e2ea17cbf41179c930ba",
"lessThan": "7475dfad10a05a5bfadebf5f2499bd61b19ed293",
"versionType": "git"
},
{
"status": "affected",
"version": "3ef240eaff36b8119ac9e2ea17cbf41179c930ba",
"lessThan": "92e47ad03e03dbb5515bdf06444bf6b1e147310d",
"versionType": "git"
},
{
"status": "affected",
"version": "3ef240eaff36b8119ac9e2ea17cbf41179c930ba",
"lessThan": "71112e62807d1925dc3ae6188b11f8cfc85aec23",
"versionType": "git"
},
{
"status": "affected",
"version": "3ef240eaff36b8119ac9e2ea17cbf41179c930ba",
"lessThan": "210d36d892de5195e6766c45519dfb1e65f3eb83",
"versionType": "git"
},
{
"status": "affected",
"version": "f2a9957e5c08b1b1caacd18a3dc4c0a1bdb7b463",
"versionType": "git"
},
{
"status": "affected",
"version": "cf16e42709aa86aa3e37f3acc3d13d5715d90096",
"versionType": "git"
},
{
"status": "affected",
"version": "61fa9f167caaa73d0a7c88f498eceeb12c6fa3db",
"versionType": "git"
},
{
"status": "affected",
"version": "7874eee0130adf9bee28e8720bb5dd051089def3",
"versionType": "git"
},
{
"status": "affected",
"version": "fc3b55ef2c840bb2746b2d8121a0788de84f7fac",
"versionType": "git"
},
{
"status": "affected",
"version": "4.4.255",
"lessThan": "4.5",
"versionType": "semver"
},
{
"status": "affected",
"version": "4.9.255",
"lessThan": "4.10",
"versionType": "semver"
},
{
"status": "affected",
"version": "4.14.158",
"lessThan": "4.15",
"versionType": "semver"
},
{
"status": "affected",
"version": "4.19.172",
"lessThan": "4.20",
"versionType": "semver"
},
{
"status": "affected",
"version": "5.4.1",
"lessThan": "5.5",
"versionType": "semver"
}
],
"programFiles": [
"kernel/futex/pi.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "5.5"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "5.5",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.253",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"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": [
"kernel/futex/pi.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-31555
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #28291 · Revision 1
- Added to Heist Feed
- Publisher date