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

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

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

is re-acquired after net_info_ratelimited(). A concurrent

ipv6_del_addr() can take the lock in that window, set ifp->state

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

addrconf_dad_failure() then overwrites DEAD with ERRDAD at errdad:

and schedules a new dad_work. The work calls ipv6_del_addr()

again, hitting the already-poisoned list entry:

general protection fault: 0000 [#1] SMP NOPTI

CPU: 4 PID: 217 Comm: kworker/4:1

Workqueue: ipv6_addrconf addrconf_dad_work

RIP: 0010:ipv6_del_addr+0xe9/0x280

RAX: dead000000000122

Call Trace:

addrconf_dad_stop+0x113/0x140

addrconf_dad_work+0x28c/0x430

process_one_work+0x1eb/0x3b0

worker_thread+0x4d/0x400

kthread+0x104/0x140

ret_from_fork+0x35/0x40

Fold the addrconf_dad_end() logic into addrconf_dad_failure() 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.