syzbot

======================================================
WARNING: possible circular locking dependency detected
6.12.0-syzkaller-05480-gfcc79e1714e8 #0 Not tainted
------------------------------------------------------
syz.4.1260/10671 is trying to acquire lock:
ffff888078f9c258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1617 [inline]
ffff888078f9c258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_kill_by_device net/ax25/af_ax25.c:101 [inline]
ffff888078f9c258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_device_event+0x24d/0x580 net/ax25/af_ax25.c:146

but task is already holding lock:
ffffffff8fef1388 (rtnl_mutex){+.+.}-{4:4}, at: dev_ioctl+0x706/0x1340 net/core/dev_ioctl.c:782

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (rtnl_mutex){+.+.}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
       ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680
       do_sock_setsockopt+0x3af/0x720 net/socket.c:2313
       __sys_setsockopt net/socket.c:2338 [inline]
       __do_sys_setsockopt net/socket.c:2344 [inline]
       __se_sys_setsockopt net/socket.c:2341 [inline]
       __x64_sys_setsockopt+0x1ee/0x280 net/socket.c:2341
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 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:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
       __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       lock_sock_nested+0x48/0x100 net/core/sock.c:3622
       lock_sock include/net/sock.h:1617 [inline]
       ax25_kill_by_device net/ax25/af_ax25.c:101 [inline]
       ax25_device_event+0x24d/0x580 net/ax25/af_ax25.c:146
       notifier_call_chain+0x19f/0x3e0 kernel/notifier.c:93
       call_netdevice_notifiers_extack net/core/dev.c:2034 [inline]
       call_netdevice_notifiers net/core/dev.c:2048 [inline]
       dev_close_many+0x33c/0x4c0 net/core/dev.c:1589
       dev_close+0x1c0/0x2c0 net/core/dev.c:1611
       bpq_device_event+0x372/0x8b0 drivers/net/hamradio/bpqether.c:547
       notifier_call_chain+0x19f/0x3e0 kernel/notifier.c:93
       __dev_notify_flags+0x207/0x400
       dev_change_flags+0xf0/0x1a0 net/core/dev.c:9020
       dev_ifsioc+0x7c8/0xe70 net/core/dev_ioctl.c:526
       dev_ioctl+0x719/0x1340 net/core/dev_ioctl.c:783
       sock_do_ioctl+0x240/0x460 net/socket.c:1223
       sock_ioctl+0x626/0x8e0 net/socket.c:1328
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 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.4.1260/10671:
 #0: ffffffff8fef1388 (rtnl_mutex){+.+.}-{4:4}, at: dev_ioctl+0x706/0x1340 net/core/dev_ioctl.c:782

stack backtrace:
CPU: 1 UID: 0 PID: 10671 Comm: syz.4.1260 Not tainted 6.12.0-syzkaller-05480-gfcc79e1714e8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206
 check_prev_add kernel/locking/lockdep.c:3161 [inline]
 check_prevs_add kernel/locking/lockdep.c:3280 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
 lock_sock_nested+0x48/0x100 net/core/sock.c:3622
 lock_sock include/net/sock.h:1617 [inline]
 ax25_kill_by_device net/ax25/af_ax25.c:101 [inline]
 ax25_device_event+0x24d/0x580 net/ax25/af_ax25.c:146
 notifier_call_chain+0x19f/0x3e0 kernel/notifier.c:93
 call_netdevice_notifiers_extack net/core/dev.c:2034 [inline]
 call_netdevice_notifiers net/core/dev.c:2048 [inline]
 dev_close_many+0x33c/0x4c0 net/core/dev.c:1589
 dev_close+0x1c0/0x2c0 net/core/dev.c:1611
 bpq_device_event+0x372/0x8b0 drivers/net/hamradio/bpqether.c:547
 notifier_call_chain+0x19f/0x3e0 kernel/notifier.c:93
 __dev_notify_flags+0x207/0x400
 dev_change_flags+0xf0/0x1a0 net/core/dev.c:9020
 dev_ifsioc+0x7c8/0xe70 net/core/dev_ioctl.c:526
 dev_ioctl+0x719/0x1340 net/core/dev_ioctl.c:783
 sock_do_ioctl+0x240/0x460 net/socket.c:1223
 sock_ioctl+0x626/0x8e0 net/socket.c:1328
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe2be780809
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe2bf669058 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fe2be945fa0 RCX: 00007fe2be780809
RDX: 0000000020000280 RSI: 0000000000008914 RDI: 000000000000000c
RBP: 00007fe2be7f393e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fe2be945fa0 R15: 00007fff26964de8
 </TASK>