Description
In the Linux kernel, the following vulnerability has been resolved:

locking/rt: Fix the incorrect RCU protection in rt_spin_unlock()

rt_spin_unlock() releases the RCU protection before unlocking the
lock. That opens the door for the following UAF scenario:

T1 T2
spin_lock(&p->lock); rcu_read_lock();
invalidate(p); p = rcu_dereference(ptr);
rcu_assign_pointer(ptr, NULL); if (!p) return;
spin_unlock(&p->lock); spin_lock(&p->lock)
lock(&lock->lock);
rcu_read_lock();
kfree_rcu(p); rcu_read_unlock();
....
spin_unlock(&p->lock)
rcu_read_unlock(); // Ends grace period
rcu_do_batch()
kfree(p);
UAF -> rt_mutex_cmpxchg_release(&lock->lock...)

Regular spinlocks keep preemption disabled accross the unlock operation,
which provides full RCU protection, but the RT substitution fails to
resemble that. Same applies for the rwlock substitution.

Move the rcu_read_unlock() invocation past the unlock operations to match
the non-RT semantics. This makes it asymmetric vs. rt_xxx_lock(), but
that's harmless as the caller needs to hold RCU read lock across the lock
operation. The migrate_enable() call stays before the unlock operation
because there is no per CPU operation in the unlock path which would
require migration to be kept disabled.
Published: 2026-08-15
Score: n/a
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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Remediation

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History

Sat, 15 Aug 2026 08:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-416

Sat, 15 Aug 2026 06:00:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: locking/rt: Fix the incorrect RCU protection in rt_spin_unlock() rt_spin_unlock() releases the RCU protection before unlocking the lock. That opens the door for the following UAF scenario: T1 T2 spin_lock(&p->lock); rcu_read_lock(); invalidate(p); p = rcu_dereference(ptr); rcu_assign_pointer(ptr, NULL); if (!p) return; spin_unlock(&p->lock); spin_lock(&p->lock) lock(&lock->lock); rcu_read_lock(); kfree_rcu(p); rcu_read_unlock(); .... spin_unlock(&p->lock) rcu_read_unlock(); // Ends grace period rcu_do_batch() kfree(p); UAF -> rt_mutex_cmpxchg_release(&lock->lock...) Regular spinlocks keep preemption disabled accross the unlock operation, which provides full RCU protection, but the RT substitution fails to resemble that. Same applies for the rwlock substitution. Move the rcu_read_unlock() invocation past the unlock operations to match the non-RT semantics. This makes it asymmetric vs. rt_xxx_lock(), but that's harmless as the caller needs to hold RCU read lock across the lock operation. The migrate_enable() call stays before the unlock operation because there is no per CPU operation in the unlock path which would require migration to be kept disabled.
Title locking/rt: Fix the incorrect RCU protection in rt_spin_unlock()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-08-15T05:52:21.752Z

Reserved: 2026-08-09T03:40:39.903Z

Link: CVE-2026-72069

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-15T06:21:16.607

Modified: 2026-08-15T06:21:16.607

Link: CVE-2026-72069

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-15T08:30:06Z

Weaknesses