CVE-2026-72069

Technical 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. T

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References