======================================================
[ INFO: possible circular locking dependency detected ]
4.4.174+ #17 Not tainted
-------------------------------------------------------
syz-executor.2/4336 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
       [<ffffffff82717d8c>] __raw_spin_lock_bh include/linux/spinlock_api_smp.h:137 [inline]
       [<ffffffff82717d8c>] _raw_spin_lock_bh+0x3c/0x50 kernel/locking/spinlock.c:175
       [<ffffffff823b3c09>] spin_lock_bh include/linux/spinlock.h:307 [inline]
       [<ffffffff823b3c09>] write_seqlock_bh include/linux/seqlock.h:457 [inline]
       [<ffffffff823b3c09>] inet_getpeer+0x5d9/0x1ce0 net/ipv4/inetpeer.c:431
       [<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
       [<ffffffff81499539>] compat_do_readv_writev+0x389/0x6e0 fs/read_write.c:984
       [<ffffffff81499c31>] compat_writev+0xe1/0x150 fs/read_write.c:1092
       [<ffffffff8149bf0b>] C_SYSC_writev fs/read_write.c:1112 [inline]
       [<ffffffff8149bf0b>] compat_SyS_writev+0xdb/0x1c0 fs/read_write.c:1101
       [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
       [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a

       [<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
       [<ffffffff8247fb9f>] udp_sendmsg+0x16cf/0x1c60 net/ipv4/udp.c:1072
       [<ffffffff826137a2>] udpv6_sendmsg+0x12f2/0x24f0 net/ipv6/udp.c:1173
       [<ffffffff824a8b42>] inet_sendmsg+0x202/0x4d0 net/ipv4/af_inet.c:755
       [<ffffffff821d838e>] sock_sendmsg_nosec net/socket.c:638 [inline]
       [<ffffffff821d838e>] sock_sendmsg+0xbe/0x110 net/socket.c:648
       [<ffffffff821d87f4>] kernel_sendmsg+0x44/0x50 net/socket.c:656
       [<ffffffff821e30a6>] sock_no_sendpage+0x116/0x150 net/core/sock.c:2283
       [<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
       [<ffffffff81530c16>] do_splice_from fs/splice.c:1128 [inline]
       [<ffffffff81530c16>] direct_splice_actor+0x126/0x1a0 fs/splice.c:1294
       [<ffffffff8153252e>] splice_direct_to_actor+0x2ce/0x850 fs/splice.c:1247
       [<ffffffff81532c55>] do_splice_direct+0x1a5/0x260 fs/splice.c:1337
       [<ffffffff8149a2fd>] do_sendfile+0x4ed/0xba0 fs/read_write.c:1229
       [<ffffffff8149c474>] C_SYSC_sendfile fs/read_write.c:1311 [inline]
       [<ffffffff8149c474>] compat_SyS_sendfile+0x144/0x160 fs/read_write.c:1294
       [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
       [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a

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 ***

4 locks held by syz-executor.2/4336:
 #0:  (rcu_read_lock_bh){......}, at: [<ffffffff823c4f7b>] ip_finish_output2+0x20b/0x1280 net/ipv4/ip_output.c:193
 #1:  (rcu_read_lock_bh){......}, at: [<ffffffff82245f57>] __dev_queue_xmit+0x1d7/0x1bb0 net/core/dev.c:3161
 #2:  (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] spin_lock include/linux/spinlock.h:302 [inline]
 #2:  (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] __netif_tx_lock include/linux/netdevice.h:3306 [inline]
 #2:  (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] sch_direct_xmit+0x238/0x700 net/sched/sch_generic.c:163
 #3:  (rcu_read_lock){......}, at: [<ffffffff82244963>] xmit_one net/core/dev.c:2776 [inline]
 #3:  (rcu_read_lock){......}, at: [<ffffffff82244963>] dev_hard_start_xmit+0xb3/0x11e0 net/core/dev.c:2797

stack backtrace:
CPU: 0 PID: 4336 Comm: syz-executor.2 Not tainted 4.4.174+ #17
 0000000000000000 96946a20c45cd7ae ffff8801d2d1e4b0 ffffffff81aad1a1
 ffffffff84057a80 ffff8801c1080000 ffffffff83af32b0 ffffffff83ad4e60
 ffffffff83af32b0 ffff8801d2d1e500 ffffffff813abcda ffff8801d2d1e5e0
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
 [<ffffffff8247fb9f>] udp_sendmsg+0x16cf/0x1c60 net/ipv4/udp.c:1072
 [<ffffffff826137a2>] udpv6_sendmsg+0x12f2/0x24f0 net/ipv6/udp.c:1173
 [<ffffffff824a8b42>] inet_sendmsg+0x202/0x4d0 net/ipv4/af_inet.c:755
 [<ffffffff821d838e>] sock_sendmsg_nosec net/socket.c:638 [inline]
 [<ffffffff821d838e>] sock_sendmsg+0xbe/0x110 net/socket.c:648
 [<ffffffff821d87f4>] kernel_sendmsg+0x44/0x50 net/socket.c:656
 [<ffffffff821e30a6>] sock_no_sendpage+0x116/0x150 net/core/sock.c:2283
 [<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
 [<ffffffff81530c16>] do_splice_from fs/splice.c:1128 [inline]
 [<ffffffff81530c16>] direct_splice_actor+0x126/0x1a0 fs/splice.c:1294
 [<ffffffff8153252e>] splice_direct_to_actor+0x2ce/0x850 fs/splice.c:1247
 [<ffffffff81532c55>] do_splice_direct+0x1a5/0x260 fs/splice.c:1337
 [<ffffffff8149a2fd>] do_sendfile+0x4ed/0xba0 fs/read_write.c:1229
 [<ffffffff8149c474>] C_SYSC_sendfile fs/read_write.c:1311 [inline]
 [<ffffffff8149c474>] compat_SyS_sendfile+0x144/0x160 fs/read_write.c:1294
 [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
 [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a
device lo entered promiscuous mode
device lo left promiscuous mode
syz-executor.2 (4336) used greatest stack depth: 22704 bytes left
device lo entered promiscuous mode
device lo entered promiscuous mode
device lo left promiscuous mode
device lo left promiscuous mode
device lo entered promiscuous mode
qtaguid: iface_stat: iface_check_stats_reset_and_adjust(lo): iface reset its stats unexpectedly
device lo entered promiscuous mode
device lo entered promiscuous mode
device lo left promiscuous mode
device lo entered promiscuous mode
device lo left promiscuous mode
device lo left promiscuous mode
device lo entered promiscuous mode
device lo entered promiscuous mode
device lo left promiscuous mode
device lo entered promiscuous mode
device lo left promiscuous mode
device lo left promiscuous mode
device lo left promiscuous mode
device lo entered promiscuous mode
device lo left promiscuous mode
device lo entered promiscuous mode
device lo entered promiscuous mode
device lo left promiscuous mode
device lo entered promiscuous mode