syzbot

IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
kworker/u4:4/75 is trying to acquire lock:
ffff88801e7299e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff88801e7299e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: unix_collect_skb+0x15a/0x550 net/unix/garbage.c:363

but task is already holding lock:
ffff88801e7289e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff88801e7289e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: unix_collect_skb+0xb7/0x550 net/unix/garbage.c:355

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(rlock-AF_UNIX);
  lock(rlock-AF_UNIX);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

4 locks held by kworker/u4:4/75:
 #0: ffff888017479138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc90001597d00 (unix_gc_work){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffffffff8de46078 (unix_gc_lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #2: ffffffff8de46078 (unix_gc_lock){+.+.}-{2:2}, at: __unix_gc+0xc4/0x19b0 net/unix/garbage.c:563
 #3: ffff88801e7289e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #3: ffff88801e7289e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: unix_collect_skb+0xb7/0x550 net/unix/garbage.c:355

stack backtrace:
CPU: 0 PID: 75 Comm: kworker/u4:4 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events_unbound __unix_gc
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 __lock_acquire+0x123e/0x7d10 kernel/locking/lockdep.c:-1
 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:351 [inline]
 unix_collect_skb+0x15a/0x550 net/unix/garbage.c:363
 __unix_walk_scc net/unix/garbage.c:486 [inline]
 unix_walk_scc net/unix/garbage.c:517 [inline]
 __unix_gc+0x1107/0x19b0 net/unix/garbage.c:575
 process_one_work+0x8a2/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1270 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>