syzbot

IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
kworker/u4:6/4424 is trying to acquire lock:
ffff0000d4bf21e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff0000d4bf21e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: unix_collect_skb+0x140/0x480 net/unix/garbage.c:361

but task is already holding lock:
ffff0000d4bf11e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff0000d4bf11e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: unix_collect_skb+0xa8/0x480 net/unix/garbage.c:353

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/u4:6/4424:
 #0: ffff0000c0029138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x6b4/0x13a8 kernel/workqueue.c:2265
 #1: ffff800020c17c20 (unix_gc_work){+.+.}-{0:0}, at: process_one_work+0x6f8/0x13a8 kernel/workqueue.c:2267
 #2: ffff800017829458 (unix_gc_lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #2: ffff800017829458 (unix_gc_lock){+.+.}-{2:2}, at: __unix_gc+0xb8/0x1334 net/unix/garbage.c:555
 #3: ffff0000d4bf11e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #3: ffff0000d4bf11e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: unix_collect_skb+0xa8/0x480 net/unix/garbage.c:353

stack backtrace:
CPU: 1 PID: 4424 Comm: kworker/u4:6 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
Workqueue: events_unbound __unix_gc
Call trace:
 dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 dump_stack+0x1c/0x5c lib/dump_stack.c:113
 __lock_acquire+0x18b4/0x6544 kernel/locking/lockdep.c:-1
 lock_acquire+0x20c/0x644 kernel/locking/lockdep.c:5662
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x54/0x6c kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:351 [inline]
 unix_collect_skb+0x140/0x480 net/unix/garbage.c:361
 __unix_walk_scc net/unix/garbage.c:484 [inline]
 unix_walk_scc net/unix/garbage.c:509 [inline]
 __unix_gc+0xd18/0x1334 net/unix/garbage.c:567
 process_one_work+0x7f4/0x13a8 kernel/workqueue.c:2292
 worker_thread+0x8c8/0xfbc kernel/workqueue.c:2439
 kthread+0x250/0x2d8 kernel/kthread.c:376
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850