syzbot

======================================================
WARNING: possible circular locking dependency detected
6.9.0-rc7-syzkaller-01862-gc85e41bfe7af #0 Not tainted
------------------------------------------------------
syz-executor.3/28728 is trying to acquire lock:
ffff888062124258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1595 [inline]
ffff888062124258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_kill_by_device net/ax25/af_ax25.c:101 [inline]
ffff888062124258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_device_event+0x24d/0x570 net/ax25/af_ax25.c:146

but task is already holding lock:
ffffffff8f5a8e88 (rtnl_mutex){+.+.}-{3:3}, at: dev_ioctl+0x706/0x1340 net/core/dev_ioctl.c:786

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (rtnl_mutex){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680
       do_sock_setsockopt+0x3af/0x720 net/socket.c:2311
       __sys_setsockopt+0x1ae/0x250 net/socket.c:2334
       __do_sys_setsockopt net/socket.c:2343 [inline]
       __se_sys_setsockopt net/socket.c:2340 [inline]
       __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2340
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (sk_lock-AF_AX25){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
       __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
       lock_sock_nested+0x48/0x100 net/core/sock.c:3534
       lock_sock include/net/sock.h:1595 [inline]
       ax25_kill_by_device net/ax25/af_ax25.c:101 [inline]
       ax25_device_event+0x24d/0x570 net/ax25/af_ax25.c:146
       notifier_call_chain+0x19f/0x3e0 kernel/notifier.c:93
       __dev_notify_flags+0x207/0x400
       dev_change_flags+0xf0/0x1a0 net/core/dev.c:8858
       dev_ifsioc+0x7c8/0xe70 net/core/dev_ioctl.c:530
       dev_ioctl+0x719/0x1340 net/core/dev_ioctl.c:787
       sock_do_ioctl+0x240/0x460 net/socket.c:1236
       sock_ioctl+0x629/0x8e0 net/socket.c:1341
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:904 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:890
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(rtnl_mutex);
                               lock(sk_lock-AF_AX25);
                               lock(rtnl_mutex);
  lock(sk_lock-AF_AX25);

 *** DEADLOCK ***

1 lock held by syz-executor.3/28728:
 #0: ffffffff8f5a8e88 (rtnl_mutex){+.+.}-{3:3}, at: dev_ioctl+0x706/0x1340 net/core/dev_ioctl.c:786

stack backtrace:
CPU: 0 PID: 28728 Comm: syz-executor.3 Not tainted 6.9.0-rc7-syzkaller-01862-gc85e41bfe7af #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
 __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
 lock_sock_nested+0x48/0x100 net/core/sock.c:3534
 lock_sock include/net/sock.h:1595 [inline]
 ax25_kill_by_device net/ax25/af_ax25.c:101 [inline]
 ax25_device_event+0x24d/0x570 net/ax25/af_ax25.c:146
 notifier_call_chain+0x19f/0x3e0 kernel/notifier.c:93
 __dev_notify_flags+0x207/0x400
 dev_change_flags+0xf0/0x1a0 net/core/dev.c:8858
 dev_ifsioc+0x7c8/0xe70 net/core/dev_ioctl.c:530
 dev_ioctl+0x719/0x1340 net/core/dev_ioctl.c:787
 sock_do_ioctl+0x240/0x460 net/socket.c:1236
 sock_ioctl+0x629/0x8e0 net/socket.c:1341
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:904 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:890
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa9c6e7dd69
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa9c7ccb0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa9c6fabf80 RCX: 00007fa9c6e7dd69
RDX: 0000000020000000 RSI: 0000000000008914 RDI: 0000000000000004
RBP: 00007fa9c6eca49e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000004d R14: 00007fa9c6fabf80 R15: 00007ffd3966b818
 </TASK>