syzbot

nft_compat: unsupported protocol 0
======================================================
WARNING: possible circular locking dependency detected
6.13.0-rc6-syzkaller-00038-g09a0fa92e5b4 #0 Not tainted
------------------------------------------------------
syz.0.1391/10276 is trying to acquire lock:
ffffffff8fedcec8 (rtnl_mutex){+.+.}-{4:4}, at: ax25_setsockopt+0x97d/0xb00 net/ax25/af_ax25.c:680

but task is already holding lock:
ffff88802e4ba258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1623 [inline]
ffff88802e4ba258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x1af/0xb00 net/ax25/af_ax25.c:574

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (sk_lock-AF_AX25){+.+.}-{0:0}:
       lock_sock_nested+0x3a/0xf0 net/core/sock.c:3625
       lock_sock include/net/sock.h:1623 [inline]
       ax25_kill_by_device net/ax25/af_ax25.c:101 [inline]
       ax25_device_event+0x2b5/0x610 net/ax25/af_ax25.c:146
       notifier_call_chain+0xb7/0x410 kernel/notifier.c:85
       call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:1996
       call_netdevice_notifiers_extack net/core/dev.c:2034 [inline]
       call_netdevice_notifiers net/core/dev.c:2048 [inline]
       __dev_notify_flags+0x1f9/0x2e0 net/core/dev.c:8992
       dev_change_flags+0x10c/0x160 net/core/dev.c:9028
       dev_ifsioc+0x9c8/0x10b0 net/core/dev_ioctl.c:526
       dev_ioctl+0x224/0x10c0 net/core/dev_ioctl.c:783
       sock_do_ioctl+0x19e/0x280 net/socket.c:1223
       sock_ioctl+0x228/0x6c0 net/socket.c:1328
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl fs/ioctl.c:892 [inline]
       __x64_sys_ioctl+0x190/0x200 fs/ioctl.c:892
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (rtnl_mutex){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain kernel/locking/lockdep.c:3904 [inline]
       __lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5226
       lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5849
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x19b/0xa60 kernel/locking/mutex.c:735
       ax25_setsockopt+0x97d/0xb00 net/ax25/af_ax25.c:680
       do_sock_setsockopt+0x222/0x480 net/socket.c:2313
       __sys_setsockopt+0x1a0/0x230 net/socket.c:2338
       __do_sys_setsockopt net/socket.c:2344 [inline]
       __se_sys_setsockopt net/socket.c:2341 [inline]
       __x64_sys_setsockopt+0xbd/0x160 net/socket.c:2341
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcd/0x250 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(sk_lock-AF_AX25);
                               lock(rtnl_mutex);
                               lock(sk_lock-AF_AX25);
  lock(rtnl_mutex);

 *** DEADLOCK ***

1 lock held by syz.0.1391/10276:
 #0: ffff88802e4ba258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1623 [inline]
 #0: ffff88802e4ba258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x1af/0xb00 net/ax25/af_ax25.c:574

stack backtrace:
CPU: 1 UID: 0 PID: 10276 Comm: syz.0.1391 Not tainted 6.13.0-rc6-syzkaller-00038-g09a0fa92e5b4 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x419/0x5d0 kernel/locking/lockdep.c:2074
 check_noncircular+0x31a/0x400 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 kernel/locking/lockdep.c:3904 [inline]
 __lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5226
 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5849
 __mutex_lock_common kernel/locking/mutex.c:585 [inline]
 __mutex_lock+0x19b/0xa60 kernel/locking/mutex.c:735
 ax25_setsockopt+0x97d/0xb00 net/ax25/af_ax25.c:680
 do_sock_setsockopt+0x222/0x480 net/socket.c:2313
 __sys_setsockopt+0x1a0/0x230 net/socket.c:2338
 __do_sys_setsockopt net/socket.c:2344 [inline]
 __se_sys_setsockopt net/socket.c:2341 [inline]
 __x64_sys_setsockopt+0xbd/0x160 net/socket.c:2341
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8dbb785d29
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:00007f8dbc592038 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007f8dbb975fa0 RCX: 00007f8dbb785d29
RDX: 0000000000000019 RSI: 0000000000000101 RDI: 000000000000000f
RBP: 00007f8dbb801b08 R08: 0000000000000010 R09: 0000000000000000
R10: 0000000020000040 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f8dbb975fa0 R15: 00007ffd4dfdb878
 </TASK>