IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): veth0: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
=============================================
[ INFO: possible recursive locking detected ]
4.1.0-syzkaller #0 Not tainted
---------------------------------------------
syz-executor/5451 is trying to acquire lock:
 (&file->mut){+.+.+.}, at: [<ffffffff81e93de2>] ucma_lock_files drivers/infiniband/core/ucma.c:1370 [inline]
 (&file->mut){+.+.+.}, at: [<ffffffff81e93de2>] ucma_migrate_id+0x1d2/0x250 drivers/infiniband/core/ucma.c:1433

but task is already holding lock:
 (&file->mut){+.+.+.}, at: [<ffffffff81e93dd8>] ucma_lock_files drivers/infiniband/core/ucma.c:1369 [inline]
 (&file->mut){+.+.+.}, at: [<ffffffff81e93dd8>] ucma_migrate_id+0x1c8/0x250 drivers/infiniband/core/ucma.c:1433

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

       CPU0
       ----
  lock(&file->mut);
  lock(&file->mut);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

1 lock held by syz-executor/5451:
 #0:  (&file->mut){+.+.+.}, at: [<ffffffff81e93dd8>] ucma_lock_files drivers/infiniband/core/ucma.c:1369 [inline]
 #0:  (&file->mut){+.+.+.}, at: [<ffffffff81e93dd8>] ucma_migrate_id+0x1c8/0x250 drivers/infiniband/core/ucma.c:1433

stack backtrace:
CPU: 1 PID: 5451 Comm: syz-executor Not tainted 4.1.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffffffff83977040 ffff8800b755bb78 ffffffff8247bc7b 0000000000000011
 ffffffff83977040 ffff8800b755bc48 ffffffff811c0c8d 000000000000c3f0
 ffffffff8388b7b0 ffff8800b755bc68 ffffffff00000000 ffff8802134bf100
Call Trace:
 [<ffffffff8247bc7b>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff8247bc7b>] dump_stack+0x4c/0x65 lib/dump_stack.c:50
 [<ffffffff811c0c8d>] print_deadlock_bug kernel/locking/lockdep.c:1752 [inline]
 [<ffffffff811c0c8d>] check_deadlock kernel/locking/lockdep.c:1796 [inline]
 [<ffffffff811c0c8d>] validate_chain kernel/locking/lockdep.c:2128 [inline]
 [<ffffffff811c0c8d>] __lock_acquire+0x1add/0x1c70 kernel/locking/lockdep.c:3205
 [<ffffffff811c18e0>] lock_acquire+0xe0/0x2f0 kernel/locking/lockdep.c:3623
 [<ffffffff82487bc0>] __mutex_lock_common kernel/locking/mutex.c:518 [inline]
 [<ffffffff82487bc0>] mutex_lock_nested+0x60/0x5c0 kernel/locking/mutex.c:617
 [<ffffffff81e93de2>] ucma_lock_files drivers/infiniband/core/ucma.c:1370 [inline]
 [<ffffffff81e93de2>] ucma_migrate_id+0x1d2/0x250 drivers/infiniband/core/ucma.c:1433
 [<ffffffff81e9361d>] ucma_write+0x6d/0xc0 drivers/infiniband/core/ucma.c:1505
 [<ffffffff812eafd3>] __vfs_write+0x23/0x100 fs/read_write.c:489
 [<ffffffff812eb6e1>] vfs_write+0xa1/0x1c0 fs/read_write.c:538
 [<ffffffff812ec384>] SYSC_write fs/read_write.c:585 [inline]
 [<ffffffff812ec384>] SyS_write+0x44/0xb0 fs/read_write.c:577
 [<ffffffff8248c1f2>] system_call_fastpath+0x16/0x7a
cfg80211: Calling CRDA to update world regulatory domain
cfg80211: Calling CRDA to update world regulatory domain
bridge0: port 2(bridge_slave_1) entered forwarding state
bridge0: port 1(bridge_slave_0) entered forwarding state
cfg80211: Exceeded CRDA call max attempts. Not calling CRDA