IPv6: ADDRCONF(NETDEV_UP): veth0: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): veth0: link is not ready

======================================================
[ INFO: possible circular locking dependency detected ]
4.4.130-g12ef385 #27 Not tainted
-------------------------------------------------------
syz-executor0/5698 is trying to acquire lock:
 (&(&q->lock)->rlock){+.-...}, at: [<ffffffff83204598>] spin_lock include/linux/spinlock.h:302 [inline]
 (&(&q->lock)->rlock){+.-...}, at: [<ffffffff83204598>] ip_defrag+0x318/0x3fe0 net/ipv4/ip_fragment.c:680

but task is already holding lock:
 (_xmit_NETROM){+.-...}, at: [<ffffffff8300f9cc>] spin_lock include/linux/spinlock.h:302 [inline]
 (_xmit_NETROM){+.-...}, at: [<ffffffff8300f9cc>] __netif_tx_lock include/linux/netdevice.h:3299 [inline]
 (_xmit_NETROM){+.-...}, at: [<ffffffff8300f9cc>] sch_direct_xmit+0x23c/0x6e0 net/sched/sch_generic.c:163

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

       [<ffffffff8123585e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff838bf14e>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:112 [inline]
       [<ffffffff838bf14e>] _raw_spin_lock_irqsave+0x4e/0x70 kernel/locking/spinlock.c:159
       [<ffffffff81eb66c1>] depot_save_stack+0x211/0x610 lib/stackdepot.c:252
       [<ffffffff814f8279>] save_stack+0xa9/0xd0 mm/kasan/kasan.c:518
       [<ffffffff814f84f7>] set_track mm/kasan/kasan.c:524 [inline]
       [<ffffffff814f84f7>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
       [<ffffffff814f8ac2>] kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:554
       [<ffffffff814f45be>] slab_post_alloc_hook mm/slub.c:1349 [inline]
       [<ffffffff814f45be>] slab_alloc_node mm/slub.c:2615 [inline]
       [<ffffffff814f45be>] slab_alloc mm/slub.c:2623 [inline]
       [<ffffffff814f45be>] kmem_cache_alloc+0xbe/0x2a0 mm/slub.c:2628
       [<ffffffff831fe0fc>] inet_getpeer.part.5+0xeac/0x15a0 net/ipv4/inetpeer.c:444
       [<ffffffff831fed4b>] inet_getpeer+0x55b/0x6f0 include/linux/seqlock.h:374
       [<ffffffff834a37d5>] inet_getpeer_v6 include/net/inetpeer.h:127 [inline]
       [<ffffffff834a37d5>] icmpv6_xrlim_allow net/ipv6/icmp.c:211 [inline]
       [<ffffffff834a37d5>] icmp6_send+0x17c5/0x1b80 net/ipv6/icmp.c:491
       [<ffffffff834a4f99>] icmpv6_param_prob+0x29/0x40 net/ipv6/icmp.c:551
       [<ffffffff834c0484>] ip6_frag_queue net/ipv6/reassembly.c:263 [inline]
       [<ffffffff834c0484>] ipv6_frag_rcv+0x3f94/0x4fd0 net/ipv6/reassembly.c:562
       [<ffffffff83433c2e>] ip6_input_finish+0x32e/0x1550 net/ipv6/ip6_input.c:248
       [<ffffffff83436c16>] NF_HOOK_THRESH include/linux/netfilter.h:226 [inline]
       [<ffffffff83436c16>] NF_HOOK include/linux/netfilter.h:249 [inline]
       [<ffffffff83436c16>] ip6_input+0xf6/0x200 net/ipv6/ip6_input.c:280
       [<ffffffff834333fd>] dst_input include/net/dst.h:504 [inline]
       [<ffffffff834333fd>] ip6_rcv_finish+0x13d/0x640 net/ipv6/ip6_input.c:62
       [<ffffffff83435f1b>] NF_HOOK_THRESH include/linux/netfilter.h:226 [inline]
       [<ffffffff83435f1b>] NF_HOOK include/linux/netfilter.h:249 [inline]
       [<ffffffff83435f1b>] ipv6_rcv+0x10cb/0x1cd0 net/ipv6/ip6_input.c:186
       [<ffffffff82f7cc06>] __netif_receive_skb_core+0x12d6/0x2940 net/core/dev.c:4019
       [<ffffffff82f7e2cb>] __netif_receive_skb+0x5b/0x1b0 net/core/dev.c:4054
       [<ffffffff82f82856>] process_backlog+0x216/0x6a0 net/core/dev.c:4647
       [<ffffffff82f7f692>] napi_poll net/core/dev.c:4885 [inline]
       [<ffffffff82f7f692>] net_rx_action+0x3a2/0xdb0 net/core/dev.c:4950
       [<ffffffff838c29ec>] __do_softirq+0x22c/0xa1a kernel/softirq.c:273
       [<ffffffff838c079c>] do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:929
       [<ffffffff8113d884>] do_softirq.part.16+0x54/0x60 kernel/softirq.c:317
       [<ffffffff8113f579>] do_softirq+0x19/0x20 kernel/softirq.c:320
       [<ffffffff82f7abac>] netif_rx_ni+0xec/0x3a0 net/core/dev.c:3653
       [<ffffffff82751a87>] tun_get_user+0xbe7/0x2410 drivers/net/tun.c:1264
       [<ffffffff827534c5>] tun_chr_write_iter+0xd5/0x190 drivers/net/tun.c:1283
       [<ffffffff8151d22c>] do_iter_readv_writev+0x13c/0x1e0 fs/read_write.c:664
       [<ffffffff8151f192>] compat_do_readv_writev+0x2e2/0x6e0 fs/read_write.c:982
       [<ffffffff8151f931>] compat_writev+0xe1/0x150 fs/read_write.c:1090
       [<ffffffff81521c48>] C_SYSC_writev fs/read_write.c:1110 [inline]
       [<ffffffff81521c48>] compat_SyS_writev+0xd8/0x1c0 fs/read_write.c:1099
       [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
       [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:459
       [<ffffffff838c0e6a>] sysenter_flags_fixed+0xd/0x17

       [<ffffffff81232712>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff81232712>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff81232712>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff81232712>] __lock_acquire+0x3902/0x5270 kernel/locking/lockdep.c:3213
       [<ffffffff8123585e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff838be636>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
       [<ffffffff838be636>] _raw_spin_lock+0x36/0x50 kernel/locking/spinlock.c:151
       [<ffffffff83204598>] spin_lock include/linux/spinlock.h:302 [inline]
       [<ffffffff83204598>] ip_defrag+0x318/0x3fe0 net/ipv4/ip_fragment.c:680
       [<ffffffff83208628>] ip_check_defrag+0x3c8/0x7e0 net/ipv4/ip_fragment.c:724
       [<ffffffff83579d2a>] packet_rcv_fanout+0x52a/0x5e0 net/packet/af_packet.c:1458
       [<ffffffff82f87764>] dev_queue_xmit_nit net/core/dev.c:1913 [inline]
       [<ffffffff82f87764>] xmit_one net/core/dev.c:2755 [inline]
       [<ffffffff82f87764>] dev_hard_start_xmit+0x644/0x11c0 net/core/dev.c:2775
       [<ffffffff8300fa51>] sch_direct_xmit+0x2c1/0x6e0 net/sched/sch_generic.c:165
       [<ffffffff82f89493>] __dev_xmit_skb net/core/dev.c:2957 [inline]
       [<ffffffff82f89493>] __dev_queue_xmit+0xef3/0x1c80 net/core/dev.c:3175
       [<ffffffff82f8a237>] dev_queue_xmit+0x17/0x20 net/core/dev.c:3241
       [<ffffffff82fa6cd7>] neigh_resolve_output+0x637/0x790 net/core/neighbour.c:1326
       [<ffffffff83213cbb>] dst_neigh_output include/net/dst.h:461 [inline]
       [<ffffffff83213cbb>] ip_finish_output2+0x6ab/0x1110 net/ipv4/ip_output.c:213
       [<ffffffff832160ab>] ip_do_fragment+0x198b/0x2150 net/ipv4/ip_output.c:633
       [<ffffffff832169b3>] ip_fragment.constprop.50+0x143/0x200 net/ipv4/ip_output.c:503
       [<ffffffff83217134>] ip_finish_output+0x6c4/0xbc0 net/ipv4/ip_output.c:286
       [<ffffffff8321a263>] NF_HOOK_COND include/linux/netfilter.h:240 [inline]
       [<ffffffff8321a263>] ip_mc_output+0x233/0x980 net/ipv4/ip_output.c:347
       [<ffffffff83217b0b>] dst_output include/net/dst.h:498 [inline]
       [<ffffffff83217b0b>] ip_local_out+0x9b/0x180 net/ipv4/ip_output.c:119
       [<ffffffff8321d7ac>] ip_send_skb+0x3c/0xc0 net/ipv4/ip_output.c:1450
       [<ffffffff832c5bd3>] udp_send_skb+0x5c3/0xc60 net/ipv4/udp.c:842
       [<ffffffff832ce78e>] udp_sendmsg+0x16ce/0x1bb0 net/ipv4/udp.c:1070
       [<ffffffff832fe2e3>] inet_sendmsg+0x203/0x4d0 net/ipv4/af_inet.c:755
       [<ffffffff82f1c3fc>] sock_sendmsg_nosec net/socket.c:625 [inline]
       [<ffffffff82f1c3fc>] sock_sendmsg+0xcc/0x110 net/socket.c:635
       [<ffffffff82f1d0dc>] SYSC_sendto+0x21c/0x370 net/socket.c:1665
       [<ffffffff82f1f760>] SyS_sendto+0x40/0x50 net/socket.c:1633
       [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
       [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:459
       [<ffffffff838c0e6a>] sysenter_flags_fixed+0xd/0x17

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-executor0/5698:
 #0:  (rcu_read_lock_bh){......}, at: [<ffffffff83213822>] ip_finish_output2+0x212/0x1110 net/ipv4/ip_output.c:193
 #1:  (rcu_read_lock_bh){......}, at: [<ffffffff82f88777>] __dev_queue_xmit+0x1d7/0x1c80 net/core/dev.c:3139
 #2:  (_xmit_NETROM){+.-...}, at: [<ffffffff8300f9cc>] spin_lock include/linux/spinlock.h:302 [inline]
 #2:  (_xmit_NETROM){+.-...}, at: [<ffffffff8300f9cc>] __netif_tx_lock include/linux/netdevice.h:3299 [inline]
 #2:  (_xmit_NETROM){+.-...}, at: [<ffffffff8300f9cc>] sch_direct_xmit+0x23c/0x6e0 net/sched/sch_generic.c:163
 #3:  (rcu_read_lock){......}, at: [<ffffffff82f871c8>] xmit_one net/core/dev.c:2754 [inline]
 #3:  (rcu_read_lock){......}, at: [<ffffffff82f871c8>] dev_hard_start_xmit+0xa8/0x11c0 net/core/dev.c:2775

stack backtrace:
CPU: 1 PID: 5698 Comm: syz-executor0 Not tainted 4.4.130-g12ef385 #27
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 87a8540291b62412 ffff8801d98cecc8 ffffffff81e0dc6d
 ffffffff853ed730 ffffffff853eb8d0 ffffffff853ed730 ffff8801d8ce2150
 ffff8801d8ce1800 ffff8801d98ced10 ffffffff8140e3eb 0000000000000003
Call Trace:
 [<ffffffff81e0dc6d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e0dc6d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8140e3eb>] print_circular_bug.cold.50+0x1bd/0x27d kernel/locking/lockdep.c:1226
 [<ffffffff81232712>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff81232712>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff81232712>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff81232712>] __lock_acquire+0x3902/0x5270 kernel/locking/lockdep.c:3213
 [<ffffffff8123585e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff838be636>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
 [<ffffffff838be636>] _raw_spin_lock+0x36/0x50 kernel/locking/spinlock.c:151
 [<ffffffff83204598>] spin_lock include/linux/spinlock.h:302 [inline]
 [<ffffffff83204598>] ip_defrag+0x318/0x3fe0 net/ipv4/ip_fragment.c:680
 [<ffffffff83208628>] ip_check_defrag+0x3c8/0x7e0 net/ipv4/ip_fragment.c:724
 [<ffffffff83579d2a>] packet_rcv_fanout+0x52a/0x5e0 net/packet/af_packet.c:1458
 [<ffffffff82f87764>] dev_queue_xmit_nit net/core/dev.c:1913 [inline]
 [<ffffffff82f87764>] xmit_one net/core/dev.c:2755 [inline]
 [<ffffffff82f87764>] dev_hard_start_xmit+0x644/0x11c0 net/core/dev.c:2775
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
 [<ffffffff8300fa51>] sch_direct_xmit+0x2c1/0x6e0 net/sched/sch_generic.c:165
 [<ffffffff82f89493>] __dev_xmit_skb net/core/dev.c:2957 [inline]
 [<ffffffff82f89493>] __dev_queue_xmit+0xef3/0x1c80 net/core/dev.c:3175
 [<ffffffff82f8a237>] dev_queue_xmit+0x17/0x20 net/core/dev.c:3241
 [<ffffffff82fa6cd7>] neigh_resolve_output+0x637/0x790 net/core/neighbour.c:1326
 [<ffffffff83213cbb>] dst_neigh_output include/net/dst.h:461 [inline]
 [<ffffffff83213cbb>] ip_finish_output2+0x6ab/0x1110 net/ipv4/ip_output.c:213
 [<ffffffff832160ab>] ip_do_fragment+0x198b/0x2150 net/ipv4/ip_output.c:633
 [<ffffffff832169b3>] ip_fragment.constprop.50+0x143/0x200 net/ipv4/ip_output.c:503
 [<ffffffff83217134>] ip_finish_output+0x6c4/0xbc0 net/ipv4/ip_output.c:286
 [<ffffffff8321a263>] NF_HOOK_COND include/linux/netfilter.h:240 [inline]
 [<ffffffff8321a263>] ip_mc_output+0x233/0x980 net/ipv4/ip_output.c:347
 [<ffffffff83217b0b>] dst_output include/net/dst.h:498 [inline]
 [<ffffffff83217b0b>] ip_local_out+0x9b/0x180 net/ipv4/ip_output.c:119
 [<ffffffff8321d7ac>] ip_send_skb+0x3c/0xc0 net/ipv4/ip_output.c:1450
 [<ffffffff832c5bd3>] udp_send_skb+0x5c3/0xc60 net/ipv4/udp.c:842
 [<ffffffff832ce78e>] udp_sendmsg+0x16ce/0x1bb0 net/ipv4/udp.c:1070
 [<ffffffff832fe2e3>] inet_sendmsg+0x203/0x4d0 net/ipv4/af_inet.c:755
 [<ffffffff82f1c3fc>] sock_sendmsg_nosec net/socket.c:625 [inline]
 [<ffffffff82f1c3fc>] sock_sendmsg+0xcc/0x110 net/socket.c:635
 [<ffffffff82f1d0dc>] SYSC_sendto+0x21c/0x370 net/socket.c:1665
 [<ffffffff82f1f760>] SyS_sendto+0x40/0x50 net/socket.c:1633
 [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
 [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:459
 [<ffffffff838c0e6a>] sysenter_flags_fixed+0xd/0x17