======================================================
[ INFO: possible circular locking dependency detected ]
4.4.174+ #4 Not tainted
-------------------------------------------------------
syz-executor.3/5963 is trying to acquire lock:
 (&(&q->lock)->rlock){+.-...}, at: [<ffffffff823ba312>] spin_lock include/linux/spinlock.h:302 [inline]
 (&(&q->lock)->rlock){+.-...}, at: [<ffffffff823ba312>] ip_defrag+0x322/0x3b70 net/ipv4/ip_fragment.c:690

but task is already holding lock:
 (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] spin_lock include/linux/spinlock.h:302 [inline]
 (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] __netif_tx_lock include/linux/netdevice.h:3306 [inline]
 (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] 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:

       [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82717e50>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:112 [inline]
       [<ffffffff82717e50>] _raw_spin_lock_irqsave+0x50/0x70 kernel/locking/spinlock.c:159
       [<ffffffff81b46dac>] depot_save_stack+0x20c/0x5f0 lib/stackdepot.c:252
       [<ffffffff81483f86>] save_stack mm/kasan/kasan.c:518 [inline]
       [<ffffffff81483f86>] set_track mm/kasan/kasan.c:524 [inline]
       [<ffffffff81483f86>] kasan_kmalloc.part.0+0xc6/0xf0 mm/kasan/kasan.c:616
       [<ffffffff81484197>] kasan_kmalloc+0xb7/0xd0 mm/kasan/kasan.c:601
       [<ffffffff8148475f>] kasan_slab_alloc+0xf/0x20 mm/kasan/kasan.c:554
       [<ffffffff8147fe9c>] slab_post_alloc_hook mm/slub.c:1349 [inline]
       [<ffffffff8147fe9c>] slab_alloc_node mm/slub.c:2615 [inline]
       [<ffffffff8147fe9c>] slab_alloc mm/slub.c:2623 [inline]
       [<ffffffff8147fe9c>] kmem_cache_alloc+0xdc/0x2c0 mm/slub.c:2628
       [<ffffffff823b4b55>] inet_getpeer+0x1525/0x1ce0 net/ipv4/inetpeer.c:444
       [<ffffffff826228ef>] inet_getpeer_v6 include/net/inetpeer.h:127 [inline]
       [<ffffffff826228ef>] icmpv6_xrlim_allow net/ipv6/icmp.c:211 [inline]
       [<ffffffff826228ef>] icmp6_send+0x178f/0x1b40 net/ipv6/icmp.c:491
       [<ffffffff82624099>] icmpv6_param_prob+0x29/0x40 net/ipv6/icmp.c:551
       [<ffffffff8263e876>] ip6_frag_queue net/ipv6/reassembly.c:225 [inline]
       [<ffffffff8263e876>] ipv6_frag_rcv+0x3f06/0x51e0 net/ipv6/reassembly.c:531
       [<ffffffff825b3c1d>] ip6_input_finish+0x57d/0x14f0 net/ipv6/ip6_input.c:248
       [<ffffffff825b66a8>] NF_HOOK_THRESH include/linux/netfilter.h:226 [inline]
       [<ffffffff825b66a8>] NF_HOOK include/linux/netfilter.h:249 [inline]
       [<ffffffff825b66a8>] ip6_input+0xf8/0x1f0 net/ipv6/ip6_input.c:280
       [<ffffffff825b317d>] dst_input include/net/dst.h:504 [inline]
       [<ffffffff825b317d>] ip6_rcv_finish+0x14d/0x670 net/ipv6/ip6_input.c:62
       [<ffffffff825b5b51>] NF_HOOK_THRESH include/linux/netfilter.h:226 [inline]
       [<ffffffff825b5b51>] NF_HOOK include/linux/netfilter.h:249 [inline]
       [<ffffffff825b5b51>] ipv6_rcv+0xfc1/0x1a20 net/ipv6/ip6_input.c:186
       [<ffffffff82230640>] __netif_receive_skb_core+0x1300/0x2950 net/core/dev.c:4041
       [<ffffffff82238bd8>] __netif_receive_skb+0x58/0x1c0 net/core/dev.c:4076
       [<ffffffff8223fec0>] process_backlog+0x200/0x630 net/core/dev.c:4673
       [<ffffffff8223f2f7>] napi_poll net/core/dev.c:4911 [inline]
       [<ffffffff8223f2f7>] net_rx_action+0x367/0xd30 net/core/dev.c:4976
       [<ffffffff8271bb16>] __do_softirq+0x226/0xa3f kernel/softirq.c:273
       [<ffffffff82719cdc>] do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:956
       [<ffffffff810e1744>] do_softirq.part.0+0x54/0x60 kernel/softirq.c:317
       [<ffffffff810e18a8>] do_softirq+0x18/0x20 kernel/softirq.c:305
       [<ffffffff8222ec4b>] netif_rx_ni+0xeb/0x3b0 net/core/dev.c:3675
       [<ffffffff81e22f6f>] tun_get_user+0xdbf/0x2640 drivers/net/tun.c:1264
       [<ffffffff81e24a0a>] tun_chr_write_iter+0xda/0x190 drivers/net/tun.c:1283
       [<ffffffff81497941>] do_iter_readv_writev+0x141/0x1e0 fs/read_write.c:666
       [<ffffffff81498cf7>] do_readv_writev+0x387/0x6e0 fs/read_write.c:810
       [<ffffffff8149917d>] vfs_writev+0x7d/0xb0 fs/read_write.c:849
       [<ffffffff8149b5fc>] SYSC_writev fs/read_write.c:882 [inline]
       [<ffffffff8149b5fc>] SyS_writev+0xdc/0x260 fs/read_write.c:874
       [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff81202d86>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff81202d86>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff81202d86>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff81202d86>] __lock_acquire+0x37d6/0x4f50 kernel/locking/lockdep.c:3213
       [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82717c98>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
       [<ffffffff82717c98>] _raw_spin_lock+0x38/0x50 kernel/locking/spinlock.c:151
       [<ffffffff823ba312>] spin_lock include/linux/spinlock.h:302 [inline]
       [<ffffffff823ba312>] ip_defrag+0x322/0x3b70 net/ipv4/ip_fragment.c:690
       [<ffffffff823bdf36>] ip_check_defrag net/ipv4/ip_fragment.c:738 [inline]
       [<ffffffff823bdf36>] ip_check_defrag+0x3d6/0x5b0 net/ipv4/ip_fragment.c:705
       [<ffffffff826dfb3e>] packet_rcv_fanout+0x51e/0x5f0 net/packet/af_packet.c:1458
       [<ffffffff82244b38>] deliver_skb net/core/dev.c:1842 [inline]
       [<ffffffff82244b38>] dev_queue_xmit_nit net/core/dev.c:1898 [inline]
       [<ffffffff82244b38>] xmit_one net/core/dev.c:2777 [inline]
       [<ffffffff82244b38>] dev_hard_start_xmit+0x288/0x11e0 net/core/dev.c:2797
       [<ffffffff822b1bd6>] sch_direct_xmit+0x2b6/0x700 net/sched/sch_generic.c:165
       [<ffffffff82246aa4>] __dev_xmit_skb net/core/dev.c:2979 [inline]
       [<ffffffff82246aa4>] __dev_queue_xmit+0xd24/0x1bb0 net/core/dev.c:3197
       [<ffffffff82247948>] dev_queue_xmit+0x18/0x20 net/core/dev.c:3263
       [<ffffffff822677e0>] neigh_resolve_output+0x4a0/0x7a0 net/core/neighbour.c:1329
       [<ffffffff823c5412>] dst_neigh_output include/net/dst.h:461 [inline]
       [<ffffffff823c5412>] ip_finish_output2+0x6a2/0x1280 net/ipv4/ip_output.c:213
       [<ffffffff823c805c>] ip_do_fragment+0x187c/0x1f70 net/ipv4/ip_output.c:635
       [<ffffffff823cbd7b>] ip_fragment.constprop.0+0x14b/0x200 net/ipv4/ip_output.c:505
       [<ffffffff823cc1e9>] ip_finish_output+0x3b9/0xc60 net/ipv4/ip_output.c:286
       [<ffffffff823cf9f1>] NF_HOOK_COND include/linux/netfilter.h:240 [inline]
       [<ffffffff823cf9f1>] ip_mc_output+0x251/0xae0 net/ipv4/ip_output.c:347
       [<ffffffff823cd21c>] dst_output include/net/dst.h:498 [inline]
       [<ffffffff823cd21c>] ip_local_out+0x9c/0x180 net/ipv4/ip_output.c:119
       [<ffffffff823d300e>] ip_send_skb+0x3e/0xc0 net/ipv4/ip_output.c:1453
       [<ffffffff82478ded>] udp_send_skb+0x4fd/0xc70 net/ipv4/udp.c:842
       [<ffffffff824795ae>] udp_push_pending_frames+0x4e/0xe0 net/ipv4/udp.c:870
       [<ffffffff8248084e>] udp_sendpage+0x2ae/0x410 net/ipv4/udp.c:1183
       [<ffffffff824aa083>] inet_sendpage+0x223/0x520 net/ipv4/af_inet.c:772
       [<ffffffff821d81b5>] kernel_sendpage+0x95/0xf0 net/socket.c:3320
       [<ffffffff821d829b>] sock_sendpage+0x8b/0xc0 net/socket.c:793
       [<ffffffff81530f1d>] pipe_to_sendpage+0x28d/0x3d0 fs/splice.c:724
       [<ffffffff81533b6e>] splice_from_pipe_feed fs/splice.c:776 [inline]
       [<ffffffff81533b6e>] __splice_from_pipe+0x37e/0x7a0 fs/splice.c:901
       [<ffffffff81536be8>] splice_from_pipe+0x108/0x170 fs/splice.c:936
       [<ffffffff81536c8c>] generic_splice_sendpage+0x3c/0x50 fs/splice.c:1109
       [<ffffffff81537d31>] do_splice_from fs/splice.c:1128 [inline]
       [<ffffffff81537d31>] do_splice fs/splice.c:1404 [inline]
       [<ffffffff81537d31>] SYSC_splice fs/splice.c:1707 [inline]
       [<ffffffff81537d31>] SyS_splice+0xd71/0x13a0 fs/splice.c:1690
       [<ffffffff82718ba1>] 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-executor.3/5963:
 #0:  (&pipe->mutex/1){+.+.+.}, at: [<ffffffff814af8b3>] pipe_lock_nested fs/pipe.c:65 [inline]
 #0:  (&pipe->mutex/1){+.+.+.}, at: [<ffffffff814af8b3>] pipe_lock+0x63/0x80 fs/pipe.c:73
 #1:  (sk_lock-AF_INET){+.+.+.}, at: [<ffffffff824806d2>] lock_sock include/net/sock.h:1497 [inline]
 #1:  (sk_lock-AF_INET){+.+.+.}, at: [<ffffffff824806d2>] udp_sendpage+0x132/0x410 net/ipv4/udp.c:1160
 #2:  (rcu_read_lock_bh){......}, at: [<ffffffff823c4f7b>] ip_finish_output2+0x20b/0x1280 net/ipv4/ip_output.c:193
 #3:  (rcu_read_lock_bh){......}, at: [<ffffffff82245f57>] __dev_queue_xmit+0x1d7/0x1bb0 net/core/dev.c:3161
 #4:  (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] spin_lock include/linux/spinlock.h:302 [inline]
 #4:  (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] __netif_tx_lock include/linux/netdevice.h:3306 [inline]
 #4:  (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] sch_direct_xmit+0x238/0x700 net/sched/sch_generic.c:163
 #5:  (rcu_read_lock){......}, at: [<ffffffff82244963>] xmit_one net/core/dev.c:2776 [inline]
 #5:  (rcu_read_lock){......}, at: [<ffffffff82244963>] dev_hard_start_xmit+0xb3/0x11e0 net/core/dev.c:2797

stack backtrace:
CPU: 1 PID: 5963 Comm: syz-executor.3 Not tainted 4.4.174+ #4
 0000000000000000 2bc8c597991eeeb7 ffff8801d5966cb0 ffffffff81aad1a1
 ffffffff84057a80 ffff8801d76c17c0 ffffffff83add3b0 ffffffff83ad51c0
 ffffffff83add3b0 ffff8801d5966d00 ffffffff813abcda ffff8801d5966de0
Call Trace:
 [<ffffffff81aad1a1>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81aad1a1>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff813abcda>] print_circular_bug.cold+0x2f7/0x44e kernel/locking/lockdep.c:1226
 [<ffffffff81202d86>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff81202d86>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff81202d86>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff81202d86>] __lock_acquire+0x37d6/0x4f50 kernel/locking/lockdep.c:3213
 [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff82717c98>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
 [<ffffffff82717c98>] _raw_spin_lock+0x38/0x50 kernel/locking/spinlock.c:151
 [<ffffffff823ba312>] spin_lock include/linux/spinlock.h:302 [inline]
 [<ffffffff823ba312>] ip_defrag+0x322/0x3b70 net/ipv4/ip_fragment.c:690
 [<ffffffff823bdf36>] ip_check_defrag net/ipv4/ip_fragment.c:738 [inline]
 [<ffffffff823bdf36>] ip_check_defrag+0x3d6/0x5b0 net/ipv4/ip_fragment.c:705
 [<ffffffff826dfb3e>] packet_rcv_fanout+0x51e/0x5f0 net/packet/af_packet.c:1458
 [<ffffffff82244b38>] deliver_skb net/core/dev.c:1842 [inline]
 [<ffffffff82244b38>] dev_queue_xmit_nit net/core/dev.c:1898 [inline]
 [<ffffffff82244b38>] xmit_one net/core/dev.c:2777 [inline]
 [<ffffffff82244b38>] dev_hard_start_xmit+0x288/0x11e0 net/core/dev.c:2797
 [<ffffffff822b1bd6>] sch_direct_xmit+0x2b6/0x700 net/sched/sch_generic.c:165
 [<ffffffff82246aa4>] __dev_xmit_skb net/core/dev.c:2979 [inline]
 [<ffffffff82246aa4>] __dev_queue_xmit+0xd24/0x1bb0 net/core/dev.c:3197
 [<ffffffff82247948>] dev_queue_xmit+0x18/0x20 net/core/dev.c:3263
 [<ffffffff822677e0>] neigh_resolve_output+0x4a0/0x7a0 net/core/neighbour.c:1329
 [<ffffffff823c5412>] dst_neigh_output include/net/dst.h:461 [inline]
 [<ffffffff823c5412>] ip_finish_output2+0x6a2/0x1280 net/ipv4/ip_output.c:213
 [<ffffffff823c805c>] ip_do_fragment+0x187c/0x1f70 net/ipv4/ip_output.c:635
 [<ffffffff823cbd7b>] ip_fragment.constprop.0+0x14b/0x200 net/ipv4/ip_output.c:505
 [<ffffffff823cc1e9>] ip_finish_output+0x3b9/0xc60 net/ipv4/ip_output.c:286
 [<ffffffff823cf9f1>] NF_HOOK_COND include/linux/netfilter.h:240 [inline]
 [<ffffffff823cf9f1>] ip_mc_output+0x251/0xae0 net/ipv4/ip_output.c:347
 [<ffffffff823cd21c>] dst_output include/net/dst.h:498 [inline]
 [<ffffffff823cd21c>] ip_local_out+0x9c/0x180 net/ipv4/ip_output.c:119
 [<ffffffff823d300e>] ip_send_skb+0x3e/0xc0 net/ipv4/ip_output.c:1453
 [<ffffffff82478ded>] udp_send_skb+0x4fd/0xc70 net/ipv4/udp.c:842
 [<ffffffff824795ae>] udp_push_pending_frames+0x4e/0xe0 net/ipv4/udp.c:870
 [<ffffffff8248084e>] udp_sendpage+0x2ae/0x410 net/ipv4/udp.c:1183
 [<ffffffff824aa083>] inet_sendpage+0x223/0x520 net/ipv4/af_inet.c:772
 [<ffffffff821d81b5>] kernel_sendpage+0x95/0xf0 net/socket.c:3320
 [<ffffffff821d829b>] sock_sendpage+0x8b/0xc0 net/socket.c:793
 [<ffffffff81530f1d>] pipe_to_sendpage+0x28d/0x3d0 fs/splice.c:724
 [<ffffffff81533b6e>] splice_from_pipe_feed fs/splice.c:776 [inline]
 [<ffffffff81533b6e>] __splice_from_pipe+0x37e/0x7a0 fs/splice.c:901
 [<ffffffff81536be8>] splice_from_pipe+0x108/0x170 fs/splice.c:936
 [<ffffffff81536c8c>] generic_splice_sendpage+0x3c/0x50 fs/splice.c:1109
 [<ffffffff81537d31>] do_splice_from fs/splice.c:1128 [inline]
 [<ffffffff81537d31>] do_splice fs/splice.c:1404 [inline]
 [<ffffffff81537d31>] SYSC_splice fs/splice.c:1707 [inline]
 [<ffffffff81537d31>] SyS_splice+0xd71/0x13a0 fs/splice.c:1690
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a