syzbot

IPv6: ADDRCONF(NETDEV_CHANGE): macvtap0: link becomes ready
batman_adv: batadv0: Interface activated: batadv_slave_1
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready
netlink: 24 bytes leftover after parsing attributes in process `syz-executor195'.
============================================
WARNING: possible recursive locking detected
4.19.211-syzkaller #0 Not tainted
--------------------------------------------
syz-executor195/8092 is trying to acquire lock:
000000008827fbb0 (rtnl_mutex){+.+.}, at: hsr_dev_destroy+0x1b/0xb0 net/hsr/hsr_device.c:373

but task is already holding lock:
000000008827fbb0 (rtnl_mutex){+.+.}, at: rtnl_lock net/core/rtnetlink.c:77 [inline]
000000008827fbb0 (rtnl_mutex){+.+.}, at: rtnetlink_rcv_msg+0x3fe/0xb80 net/core/rtnetlink.c:4779

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

       CPU0
       ----
  lock(rtnl_mutex);
  lock(rtnl_mutex);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

1 lock held by syz-executor195/8092:
 #0: 000000008827fbb0 (rtnl_mutex){+.+.}, at: rtnl_lock net/core/rtnetlink.c:77 [inline]
 #0: 000000008827fbb0 (rtnl_mutex){+.+.}, at: rtnetlink_rcv_msg+0x3fe/0xb80 net/core/rtnetlink.c:4779

stack backtrace:
CPU: 0 PID: 8092 Comm: syz-executor195 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
 print_deadlock_bug kernel/locking/lockdep.c:1764 [inline]
 check_deadlock kernel/locking/lockdep.c:1808 [inline]
 validate_chain kernel/locking/lockdep.c:2404 [inline]
 __lock_acquire.cold+0x121/0x57e kernel/locking/lockdep.c:3416
 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
 __mutex_lock_common kernel/locking/mutex.c:937 [inline]
 __mutex_lock+0xd7/0x1190 kernel/locking/mutex.c:1078
 hsr_dev_destroy+0x1b/0xb0 net/hsr/hsr_device.c:373
 register_netdevice+0x901/0x10f0 net/core/dev.c:8791
 hsr_dev_finalize+0x4f5/0x770 net/hsr/hsr_device.c:491
 hsr_newlink+0x27d/0x3e0 net/hsr/hsr_netlink.c:78
 rtnl_newlink+0x1030/0x15c0 net/core/rtnetlink.c:3141
 rtnetlink_rcv_msg+0x453/0xb80 net/core/rtnetlink.c:4782
 netlink_rcv_skb+0x160/0x440 net/netlink/af_netlink.c:2463
 netlink_unicast_kernel net/netlink/af_netlink.c:1325 [inline]
 netlink_unicast+0x4d5/0x690 net/netlink/af_netlink.c:1351
 netlink_sendmsg+0x6c3/0xc50 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg+0xc3/0x120 net/socket.c:661
 ___sys_sendmsg+0x7bb/0x8e0 net/socket.c:2227
 __sys_sendmsg net/socket.c:2265 [inline]
 __do_sys_sendmsg net/socket.c:2274 [inline]
 __se_sys_sendmsg net/socket.c:2272 [inline]
 __x64_sys_sendmsg+0x132/0x220 net/socket.c:2272
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f9b1ba70869
Code: 28 c3 e8 4a 15 00 00 66 2e 0f 1f 84 00 00 00 00 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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff7b20a388 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fff7b20a398 RCX: 00007f9b1ba70869
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000004
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff7b20a3a0
R13: 00007fff7b20a3c0 R14: 0000000000000000 R15: 0000000000000000