======================================================
[ INFO: possible circular locking dependency detected ]
4.4.171+ #11 Not tainted
-------------------------------------------------------
syz-executor4/5287 is trying to acquire lock:
 (&(&q->lock)->rlock){+.-...}, at: [<ffffffff823b985a>] spin_lock include/linux/spinlock.h:302 [inline]
 (&(&q->lock)->rlock){+.-...}, at: [<ffffffff823b985a>] ip_defrag+0x32a/0x3dd0 net/ipv4/ip_fragment.c:680

but task is already holding lock:
 (_xmit_NETROM){+.-...}, at: [<ffffffff822b0e48>] spin_lock include/linux/spinlock.h:302 [inline]
 (_xmit_NETROM){+.-...}, at: [<ffffffff822b0e48>] __netif_tx_lock include/linux/netdevice.h:3306 [inline]
 (_xmit_NETROM){+.-...}, at: [<ffffffff822b0e48>] sch_direct_xmit+0x238/0x700 net/sched/sch_generic.c:163

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

       [<ffffffff81205d5e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82716ef0>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:112 [inline]
       [<ffffffff82716ef0>] _raw_spin_lock_irqsave+0x50/0x70 kernel/locking/spinlock.c:159
       [<ffffffff815722fa>] ep_poll_callback+0x6a/0x760 fs/eventpoll.c:1012
       [<ffffffff811e8b70>] __wake_up_common+0xc0/0x160 kernel/sched/wait.c:73
       [<ffffffff811e8c44>] __wake_up+0x34/0x50 kernel/sched/wait.c:95
       [<ffffffff81f8e605>] mousedev_write+0x605/0x7d0 drivers/input/mousedev.c:713
       [<ffffffff814962c6>] __vfs_write+0x116/0x3d0 fs/read_write.c:489
       [<ffffffff81497fc2>] vfs_write+0x182/0x4e0 fs/read_write.c:538
       [<ffffffff8149a5fc>] SYSC_write fs/read_write.c:585 [inline]
       [<ffffffff8149a5fc>] SyS_write+0xdc/0x1c0 fs/read_write.c:577
       [<ffffffff82717c21>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff81202b76>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff81202b76>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff81202b76>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff81202b76>] __lock_acquire+0x37d6/0x4f50 kernel/locking/lockdep.c:3213
       [<ffffffff81205d5e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82716d38>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
       [<ffffffff82716d38>] _raw_spin_lock+0x38/0x50 kernel/locking/spinlock.c:151
binder_alloc: 1628: binder_alloc_buf, no vma
binder: 5278:5300 transaction failed 29189/-3, size 0-0 line 3137
binder: 5278:5281 ioctl 40046207 0 returned -16
       [<ffffffff823b985a>] spin_lock include/linux/spinlock.h:302 [inline]
       [<ffffffff823b985a>] ip_defrag+0x32a/0x3dd0 net/ipv4/ip_fragment.c:680
       [<ffffffff823bd6d6>] ip_check_defrag net/ipv4/ip_fragment.c:728 [inline]
       [<ffffffff823bd6d6>] ip_check_defrag+0x3d6/0x740 net/ipv4/ip_fragment.c:695
       [<ffffffff826dee4e>] packet_rcv_fanout+0x51e/0x5f0 net/packet/af_packet.c:1458
       [<ffffffff82243e28>] deliver_skb net/core/dev.c:1842 [inline]
       [<ffffffff82243e28>] dev_queue_xmit_nit net/core/dev.c:1898 [inline]
       [<ffffffff82243e28>] xmit_one net/core/dev.c:2777 [inline]
       [<ffffffff82243e28>] dev_hard_start_xmit+0x288/0x11e0 net/core/dev.c:2797
       [<ffffffff822b0ec6>] sch_direct_xmit+0x2b6/0x700 net/sched/sch_generic.c:165
       [<ffffffff82245d94>] __dev_xmit_skb net/core/dev.c:2979 [inline]
       [<ffffffff82245d94>] __dev_queue_xmit+0xd24/0x1bb0 net/core/dev.c:3197
       [<ffffffff82246c38>] dev_queue_xmit+0x18/0x20 net/core/dev.c:3263
       [<ffffffff82266ad0>] neigh_resolve_output+0x4a0/0x7a0 net/core/neighbour.c:1329
       [<ffffffff823c4d92>] dst_neigh_output include/net/dst.h:461 [inline]
       [<ffffffff823c4d92>] ip_finish_output2+0x6a2/0x1280 net/ipv4/ip_output.c:213
       [ 1976.907358] binder: undelivered TRANSACTION_ERROR: 29189
[<ffffffff823c79dc>] ip_do_fragment+0x187c/0x1f70 net/ipv4/ip_output.c:635
       [<ffffffff823cb6fb>] ip_fragment.constprop.0+0x14b/0x200 net/ipv4/ip_output.c:505
       [<ffffffff823cbb69>] ip_finish_output+0x3b9/0xc60 net/ipv4/ip_output.c:286
       [<ffffffff823cf371>] NF_HOOK_COND include/linux/netfilter.h:240 [inline]
       [<ffffffff823cf371>] ip_mc_output+0x251/0xae0 net/ipv4/ip_output.c:347
       [<ffffffff823ccb9c>] dst_output include/net/dst.h:498 [inline]
       [<ffffffff823ccb9c>] ip_local_out+0x9c/0x180 net/ipv4/ip_output.c:119
       [<ffffffff823d298e>] ip_send_skb+0x3e/0xc0 net/ipv4/ip_output.c:1453
       [<ffffffff8247880d>] udp_send_skb+0x4fd/0xc70 net/ipv4/udp.c:842
       [<ffffffff82478fce>] udp_push_pending_frames+0x4e/0xe0 net/ipv4/udp.c:870
       [<ffffffff8248026e>] udp_sendpage+0x2ae/0x410 net/ipv4/udp.c:1183
       [<ffffffff824a9cd3>] inet_sendpage+0x223/0x520 net/ipv4/af_inet.c:772
       [<ffffffff821d75f5>] kernel_sendpage+0x95/0xf0 net/socket.c:3320
       [<ffffffff821d76db>] sock_sendpage+0x8b/0xc0 net/socket.c:793
       [<ffffffff8153086d>] pipe_to_sendpage+0x28d/0x3d0 fs/splice.c:724
       [<ffffffff815334be>] splice_from_pipe_feed fs/splice.c:776 [inline]
       [<ffffffff815334be>] __splice_from_pipe+0x37e/0x7a0 fs/splice.c:901
       [<ffffffff81536538>] splice_from_pipe+0x108/0x170 fs/splice.c:936
       [<ffffffff815365dc>] generic_splice_sendpage+0x3c/0x50 fs/splice.c:1109
       [<ffffffff81537681>] do_splice_from fs/splice.c:1128 [inline]
       [<ffffffff81537681>] do_splice fs/splice.c:1404 [inline]
       [<ffffffff81537681>] SYSC_splice fs/splice.c:1707 [inline]
       [<ffffffff81537681>] SyS_splice+0xd71/0x13a0 fs/splice.c:1690
       [<ffffffff82717c21>] entry_SYSCALL_64_fastpath+0x1e/0x9a

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(_xmit_NETROM);
                               lock(&(&q->lock)->rlock);
                               lock(_xmit_NETROM);
  lock(&(&q->lock)->rlock);

 *** DEADLOCK ***

6 locks held by syz-executor4/5287:
 #0:  (&pipe->mutex/1){+.+.+.}, at: [<ffffffff814af203>] pipe_lock_nested fs/pipe.c:65 [inline]
 #0:  (&pipe->mutex/1){+.+.+.}, at: [<ffffffff814af203>] pipe_lock+0x63/0x80 fs/pipe.c:73
 #1:  (sk_lock-AF_INET){+.+.+.}, at: [<ffffffff824800f2>] lock_sock include/net/sock.h:1497 [inline]
 #1:  (sk_lock-AF_INET){+.+.+.}, at: [<ffffffff824800f2>] udp_sendpage+0x132/0x410 net/ipv4/udp.c:1160
 #2:  (rcu_read_lock_bh){......}, at: [<ffffffff823c48fb>] ip_finish_output2+0x20b/0x1280 net/ipv4/ip_output.c:193
 #3:  (rcu_read_lock_bh){......}, at: [<ffffffff82245247>] __dev_queue_xmit+0x1d7/0x1bb0 net/core/dev.c:3161
 #4:  (_xmit_NETROM){+.-...}, at: [<ffffffff822b0e48>] spin_lock include/linux/spinlock.h:302 [inline]
 #4:  (_xmit_NETROM){+.-...}, at: [<ffffffff822b0e48>] __netif_tx_lock include/linux/netdevice.h:3306 [inline]
 #4:  (_xmit_NETROM){+.-...}, at: [<ffffffff822b0e48>] sch_direct_xmit+0x238/0x700 net/sched/sch_generic.c:163
 #5:  (rcu_read_lock){......}, at: [<ffffffff82243c53>] xmit_one net/core/dev.c:2776 [inline]
 #5:  (rcu_read_lock){......}, at: [<ffffffff82243c53>] dev_hard_start_xmit+0xb3/0x11e0 net/core/dev.c:2797

stack backtrace:
CPU: 1 PID: 5287 Comm: syz-executor4 Not tainted 4.4.171+ #11
 0000000000000000 52291dfbd3dd5881 ffff8800aac96ce0 ffffffff81aaca21
 ffffffff84057a80 ffff88009f454740 ffffffff83af0be0 ffffffff83ad5010
 ffffffff83af0be0 ffff8800aac96d30 ffffffff813abad4 ffff8800aac96e10
Call Trace:
 [<ffffffff81aaca21>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81aaca21>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff813abad4>] print_circular_bug.cold+0x2f7/0x44e kernel/locking/lockdep.c:1226
 [<ffffffff81202b76>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff81202b76>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff81202b76>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff81202b76>] __lock_acquire+0x37d6/0x4f50 kernel/locking/lockdep.c:3213
 [<ffffffff81205d5e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff82716d38>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
 [<ffffffff82716d38>] _raw_spin_lock+0x38/0x50 kernel/locking/spinlock.c:151
 [<ffffffff823b985a>] spin_lock include/linux/spinlock.h:302 [inline]
 [<ffffffff823b985a>] ip_defrag+0x32a/0x3dd0 net/ipv4/ip_fragment.c:680
 [<ffffffff823bd6d6>] ip_check_defrag net/ipv4/ip_fragment.c:728 [inline]
 [<ffffffff823bd6d6>] ip_check_defrag+0x3d6/0x740 net/ipv4/ip_fragment.c:695
 [<ffffffff826dee4e>] packet_rcv_fanout+0x51e/0x5f0 net/packet/af_packet.c:1458
 [<ffffffff82243e28>] deliver_skb net/core/dev.c:1842 [inline]
 [<ffffffff82243e28>] dev_queue_xmit_nit net/core/dev.c:1898 [inline]
 [<ffffffff82243e28>] xmit_one net/core/dev.c:2777 [inline]
 [<ffffffff82243e28>] dev_hard_start_xmit+0x288/0x11e0 net/core/dev.c:2797
 [<ffffffff822b0ec6>] sch_direct_xmit+0x2b6/0x700 net/sched/sch_generic.c:165
 [<ffffffff82245d94>] __dev_xmit_skb net/core/dev.c:2979 [inline]
 [<ffffffff82245d94>] __dev_queue_xmit+0xd24/0x1bb0 net/core/dev.c:3197
 [<ffffffff82246c38>] dev_queue_xmit+0x18/0x20 net/core/dev.c:3263
 [<ffffffff82266ad0>] neigh_resolve_output+0x4a0/0x7a0 net/core/neighbour.c:1329
 [<ffffffff823c4d92>] dst_neigh_output include/net/dst.h:461 [inline]
 [<ffffffff823c4d92>] ip_finish_output2+0x6a2/0x1280 net/ipv4/ip_output.c:213
 [<ffffffff823c79dc>] ip_do_fragment+0x187c/0x1f70 net/ipv4/ip_output.c:635
 [<ffffffff823cb6fb>] ip_fragment.constprop.0+0x14b/0x200 net/ipv4/ip_output.c:505
 [<ffffffff823cbb69>] ip_finish_output+0x3b9/0xc60 net/ipv4/ip_output.c:286
 [<ffffffff823cf371>] NF_HOOK_COND include/linux/netfilter.h:240 [inline]
 [<ffffffff823cf371>] ip_mc_output+0x251/0xae0 net/ipv4/ip_output.c:347
 [<ffffffff823ccb9c>] dst_output include/net/dst.h:498 [inline]
 [<ffffffff823ccb9c>] ip_local_out+0x9c/0x180 net/ipv4/ip_output.c:119
 [<ffffffff823d298e>] ip_send_skb+0x3e/0xc0 net/ipv4/ip_output.c:1453
 [<ffffffff8247880d>] udp_send_skb+0x4fd/0xc70 net/ipv4/udp.c:842
 [<ffffffff82478fce>] udp_push_pending_frames+0x4e/0xe0 net/ipv4/udp.c:870
 [<ffffffff8248026e>] udp_sendpage+0x2ae/0x410 net/ipv4/udp.c:1183
 [<ffffffff824a9cd3>] inet_sendpage+0x223/0x520 net/ipv4/af_inet.c:772
 [<ffffffff821d75f5>] kernel_sendpage+0x95/0xf0 net/socket.c:3320
 [<ffffffff821d76db>] sock_sendpage+0x8b/0xc0 net/socket.c:793
 [<ffffffff8153086d>] pipe_to_sendpage+0x28d/0x3d0 fs/splice.c:724
 [<ffffffff815334be>] splice_from_pipe_feed fs/splice.c:776 [inline]
 [<ffffffff815334be>] __splice_from_pipe+0x37e/0x7a0 fs/splice.c:901
 [<ffffffff81536538>] splice_from_pipe+0x108/0x170 fs/splice.c:936
 [<ffffffff815365dc>] generic_splice_sendpage+0x3c/0x50 fs/splice.c:1109
 [<ffffffff81537681>] do_splice_from fs/splice.c:1128 [inline]
 [<ffffffff81537681>] do_splice fs/splice.c:1404 [inline]
 [<ffffffff81537681>] SYSC_splice fs/splice.c:1707 [inline]
 [<ffffffff81537681>] SyS_splice+0xd71/0x13a0 fs/splice.c:1690
 [<ffffffff82717c21>] entry_SYSCALL_64_fastpath+0x1e/0x9a