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* possible deadlock in rxrpc_put_peer
@ 2019-07-26  9:38 syzbot
  2019-07-26 10:59 ` Dmitry Vyukov
  0 siblings, 1 reply; 2+ messages in thread
From: syzbot @ 2019-07-26  9:38 UTC (permalink / raw)
  To: linux-kernel, syzkaller-bugs

Hello,

syzbot found the following crash on:

HEAD commit:    6d21a41b Add linux-next specific files for 20190718
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=174e3af0600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3430a151e1452331
dashboard link: https://syzkaller.appspot.com/bug?extid=72af434e4b3417318f84
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+72af434e4b3417318f84@syzkaller.appspotmail.com

============================================
WARNING: possible recursive locking detected
5.2.0-next-20190718 #41 Not tainted
--------------------------------------------
kworker/0:3/21678 is trying to acquire lock:
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at: spin_lock_bh  
/./include/linux/spinlock.h:343 [inline]
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:  
__rxrpc_put_peer /net/rxrpc/peer_object.c:415 [inline]
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:  
rxrpc_put_peer+0x2d3/0x6a0 /net/rxrpc/peer_object.c:435

but task is already holding lock:
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at: spin_lock_bh  
/./include/linux/spinlock.h:343 [inline]
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:  
rxrpc_peer_keepalive_dispatch /net/rxrpc/peer_event.c:378 [inline]
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:  
rxrpc_peer_keepalive_worker+0x6b3/0xd02 /net/rxrpc/peer_event.c:430

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

        CPU0
        ----
   lock(&(&rxnet->peer_hash_lock)->rlock);
   lock(&(&rxnet->peer_hash_lock)->rlock);

  *** DEADLOCK ***

  May be due to missing lock nesting notation

3 locks held by kworker/0:3/21678:
  #0: 000000007c4c2bc3 ((wq_completion)krxrpcd){+.+.}, at: __write_once_size  
/./include/linux/compiler.h:226 [inline]
  #0: 000000007c4c2bc3 ((wq_completion)krxrpcd){+.+.}, at: arch_atomic64_set  
/./arch/x86/include/asm/atomic64_64.h:34 [inline]
  #0: 000000007c4c2bc3 ((wq_completion)krxrpcd){+.+.}, at: atomic64_set  
/./include/asm-generic/atomic-instrumented.h:855 [inline]
  #0: 000000007c4c2bc3 ((wq_completion)krxrpcd){+.+.}, at: atomic_long_set  
/./include/asm-generic/atomic-long.h:40 [inline]
  #0: 000000007c4c2bc3 ((wq_completion)krxrpcd){+.+.}, at: set_work_data  
/kernel/workqueue.c:620 [inline]
  #0: 000000007c4c2bc3 ((wq_completion)krxrpcd){+.+.}, at:  
set_work_pool_and_clear_pending /kernel/workqueue.c:647 [inline]
  #0: 000000007c4c2bc3 ((wq_completion)krxrpcd){+.+.}, at:  
process_one_work+0x88b/0x1740 /kernel/workqueue.c:2240
  #1: 000000006782bc7f  
((work_completion)(&rxnet->peer_keepalive_work)){+.+.}, at:  
process_one_work+0x8c1/0x1740 /kernel/workqueue.c:2244
  #2: 00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:  
spin_lock_bh /./include/linux/spinlock.h:343 [inline]
  #2: 00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:  
rxrpc_peer_keepalive_dispatch /net/rxrpc/peer_event.c:378 [inline]
  #2: 00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:  
rxrpc_peer_keepalive_worker+0x6b3/0xd02 /net/rxrpc/peer_event.c:430

stack backtrace:
CPU: 0 PID: 21678 Comm: kworker/0:3 Not tainted 5.2.0-next-20190718 #41
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: krxrpcd rxrpc_peer_keepalive_worker
Call Trace:
  __dump_stack /lib/dump_stack.c:77 [inline]
  dump_stack+0x172/0x1f0 /lib/dump_stack.c:113
  print_deadlock_bug /kernel/locking/lockdep.c:2301 [inline]
  check_deadlock /kernel/locking/lockdep.c:2342 [inline]
  validate_chain /kernel/locking/lockdep.c:2881 [inline]
  __lock_acquire.cold+0x194/0x398 /kernel/locking/lockdep.c:3880
  lock_acquire+0x190/0x410 /kernel/locking/lockdep.c:4413
  __raw_spin_lock_bh /./include/linux/spinlock_api_smp.h:135 [inline]
  _raw_spin_lock_bh+0x33/0x50 /kernel/locking/spinlock.c:175
  spin_lock_bh /./include/linux/spinlock.h:343 [inline]
  __rxrpc_put_peer /net/rxrpc/peer_object.c:415 [inline]
  rxrpc_put_peer+0x2d3/0x6a0 /net/rxrpc/peer_object.c:435
  rxrpc_peer_keepalive_dispatch /net/rxrpc/peer_event.c:381 [inline]
  rxrpc_peer_keepalive_worker+0x7a6/0xd02 /net/rxrpc/peer_event.c:430
  process_one_work+0x9af/0x1740 /kernel/workqueue.c:2269
  worker_thread+0x98/0xe40 /kernel/workqueue.c:2415
  kthread+0x361/0x430 /kernel/kthread.c:255
  ret_from_fork+0x24/0x30 /arch/x86/entry/entry_64.S:352


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

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2019-07-26  9:38 possible deadlock in rxrpc_put_peer syzbot
2019-07-26 10:59 ` Dmitry Vyukov

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