tpacket_rcv: packet too big, clamped from 65589 to 65406. macoff=82
======================================================
[ INFO: possible circular locking dependency detected ]
4.4.171+ #11 Not tainted
-------------------------------------------------------
syz-executor0/17242 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
       [<ffffffff81afd550>] __do_once_start+0x20/0xc0 lib/once.c:39
       [<ffffffff82691424>] nf_hash_frag+0x84/0x270 net/ipv6/netfilter/nf_conntrack_reasm.c:159
       [<ffffffff8269165e>] nf_hashfn+0x4e/0x70 net/ipv6/netfilter/nf_conntrack_reasm.c:170
       [<ffffffff824e060c>] inet_frag_hashfn net/ipv4/inet_fragment.c:58 [inline]
       [<ffffffff824e060c>] get_frag_bucket_locked+0x12c/0x200 net/ipv4/inet_fragment.c:255
       [<ffffffff824e1895>] fq_unlink net/ipv4/inet_fragment.c:271 [inline]
       [<ffffffff824e1895>] inet_frag_kill net/ipv4/inet_fragment.c:283 [inline]
       [<ffffffff824e1895>] inet_frag_kill+0x85/0x1d0 net/ipv4/inet_fragment.c:277
       [<ffffffff8269298d>] nf_ct_frag6_reasm net/ipv6/netfilter/nf_conntrack_reasm.c:386 [inline]
       [<ffffffff8269298d>] nf_ct_frag6_gather+0x130d/0x3430 net/ipv6/netfilter/nf_conntrack_reasm.c:623
       [<ffffffff82690f84>] ipv6_defrag+0x214/0x5d0 net/ipv6/netfilter/nf_defrag_ipv6_hooks.c:66
       [<ffffffff822f77f6>] nf_iterate+0x186/0x220 net/netfilter/core.c:274
       [<ffffffff822f7a46>] nf_hook_slow+0x1b6/0x340 net/netfilter/core.c:306
       [<ffffffff825b4db4>] nf_hook_thresh include/linux/netfilter.h:187 [inline]
       [<ffffffff825b4db4>] NF_HOOK_THRESH include/linux/netfilter.h:224 [inline]
       [<ffffffff825b4db4>] NF_HOOK include/linux/netfilter.h:249 [inline]
       [<ffffffff825b4db4>] ipv6_rcv+0x14b4/0x1bb0 net/ipv6/ip6_input.c:186
       [<ffffffff8222f930>] __netif_receive_skb_core+0x1300/0x2950 net/core/dev.c:4041
       [<ffffffff82237ec8>] __netif_receive_skb+0x58/0x1c0 net/core/dev.c:4076
       [<ffffffff8223f1b0>] process_backlog+0x200/0x630 net/core/dev.c:4673
       [<ffffffff8223e5e7>] napi_poll net/core/dev.c:4911 [inline]
       [<ffffffff8223e5e7>] net_rx_action+0x367/0xd30 net/core/dev.c:4976
       [<ffffffff8271ab96>] __do_softirq+0x226/0xa3f kernel/softirq.c:273
       [<ffffffff82718d5c>] do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:956
       [<ffffffff810e1534>] do_softirq.part.0+0x54/0x60 kernel/softirq.c:317
       [<ffffffff810e1698>] do_softirq+0x18/0x20 kernel/softirq.c:305
       [<ffffffff8222df3b>] netif_rx_ni+0xeb/0x3b0 net/core/dev.c:3675
       [<ffffffff81e2272f>] tun_get_user+0xdbf/0x2640 drivers/net/tun.c:1264
       [<ffffffff81e241ca>] tun_chr_write_iter+0xda/0x190 drivers/net/tun.c:1283
       [<ffffffff814972f1>] do_iter_readv_writev+0x141/0x1e0 fs/read_write.c:664
       [<ffffffff814986a7>] do_readv_writev+0x387/0x6e0 fs/read_write.c:808
       [<ffffffff81498b2d>] vfs_writev+0x7d/0xb0 fs/read_write.c:847
       [<ffffffff8149afac>] SYSC_writev fs/read_write.c:880 [inline]
       [<ffffffff8149afac>] SyS_writev+0xdc/0x260 fs/read_write.c:872
       [<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
       [<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
       [<ffffffff823c52e2>] neigh_hh_output include/net/neighbour.h:486 [inline]
       [<ffffffff823c52e2>] dst_neigh_output include/net/dst.h:459 [inline]
       [<ffffffff823c52e2>] ip_finish_output2+0xbf2/0x1280 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

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-executor0/17242:
 #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: 17242 Comm: syz-executor0 Not tainted 4.4.171+ #11
 0000000000000000 186336b95909dc72 ffff8800b4c0ed70 ffffffff81aaca21
 ffffffff84057a80 ffff8801d5c6c740 ffffffff83b00240 ffffffff83ad5010
 ffffffff83b00240 ffff8800b4c0edc0 ffffffff813abad4 ffff8800b4c0eea0
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
 [<ffffffff823c52e2>] neigh_hh_output include/net/neighbour.h:486 [inline]
 [<ffffffff823c52e2>] dst_neigh_output include/net/dst.h:459 [inline]
 [<ffffffff823c52e2>] ip_finish_output2+0xbf2/0x1280 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
audit_printk_skb: 42 callbacks suppressed
audit: type=1400 audit(1548019317.672:2708): avc:  denied  { create } for  pid=17516 comm="syz-executor4" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
audit: type=1400 audit(1548019317.862:2709): avc:  denied  { write } for  pid=17516 comm="syz-executor4" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
audit: type=1400 audit(1548019317.932:2710): avc:  denied  { read } for  pid=17516 comm="syz-executor4" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
audit: type=1400 audit(1548019318.452:2711): avc:  denied  { create } for  pid=17516 comm="syz-executor4" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
audit: type=1400 audit(1548019318.482:2712): avc:  denied  { write } for  pid=17516 comm="syz-executor4" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
audit: type=1400 audit(1548019318.952:2713): avc:  denied  { create } for  pid=17572 comm="syz-executor4" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
audit: type=1400 audit(1548019318.972:2714): avc:  denied  { write } for  pid=17572 comm="syz-executor4" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
audit: type=1400 audit(1548019319.012:2715): avc:  denied  { read } for  pid=17572 comm="syz-executor4" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
audit: type=1400 audit(1548019319.362:2716): avc:  denied  { create } for  pid=17572 comm="syz-executor4" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
audit: type=1400 audit(1548019319.432:2717): avc:  denied  { write } for  pid=17572 comm="syz-executor4" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1