CVE-2026-74398

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

ipv6: addrconf: bail out of dad_failure when state is no longer POSTDAD

addrconfdadfailure() transitions ifp->state from DAD to POSTDAD

via addrconfdadend(), which drops ifp->lock on return.  The lock

is re-acquired after netinforatelimited().  A concurrent

ipv6deladdr() can take the lock in that window, set ifp->state

to DEAD and run listdelrcu(&ifp->if_list).

addrconfdadfailure() then overwrites DEAD with ERRDAD at errdad:

and schedules a new dadwork.  The work calls ipv6del_addr()

again, hitting the already-poisoned list entry:

  general protection fault: 0000 [#1] SMP NOPTI

  CPU: 4 PID: 217 Comm: kworker/4:1

  Workqueue: ipv6addrconf addrconfdad_work

  RIP: 0010:ipv6deladdr+0xe9/0x280

  RAX: dead000000000122

  Call Trace:

   addrconfdadstop+0x113/0x140

   addrconfdadwork+0x28c/0x430

   processonework+0x1eb/0x3b0

   worker_thread+0x4d/0x400

   kthread+0x104/0x140

   retfromfork+0x35/0x40

Fold the addrconfdadend() logic into addrconfdadfailure() under

a single ifp->lock critical section.  The STABLE_PRIVACY branch

temporarily drops ifp->lock around address regeneration, so at

lock_errdad: verify the state is still POSTDAD before transitioning

to ERRDAD; bail out otherwise to avoid overwriting a state set by

another path while the lock was released.