======================================================
[ INFO: possible circular locking dependency detected ]
4.4.159+ #108 Not tainted
-------------------------------------------------------
syz-executor265/2077 is trying to acquire lock:
 (&(&q->lock)->rlock){+.-...}, at: [<ffffffff823a76cb>] spin_lock include/linux/spinlock.h:302 [inline]
 (&(&q->lock)->rlock){+.-...}, at: [<ffffffff823a76cb>] ip_defrag+0x31b/0x40c0 net/ipv4/ip_fragment.c:680

but task is already holding lock:
 (_xmit_NETROM){+.-...}, at: [<ffffffff8229dbc3>] spin_lock include/linux/spinlock.h:302 [inline]
 (_xmit_NETROM){+.-...}, at: [<ffffffff8229dbc3>] __netif_tx_lock include/linux/netdevice.h:3299 [inline]
 (_xmit_NETROM){+.-...}, at: [<ffffffff8229dbc3>] sch_direct_xmit+0x233/0x6c0 net/sched/sch_generic.c:163

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

       [<ffffffff81202efe>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82704f8e>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:112 [inline]
       [<ffffffff82704f8e>] _raw_spin_lock_irqsave+0x4e/0x70 kernel/locking/spinlock.c:159
       [<ffffffff81b34a6b>] depot_save_stack+0x20b/0x5eb lib/stackdepot.c:252
       [<ffffffff8147e849>] save_stack mm/kasan/kasan.c:518 [inline]
       [<ffffffff8147e849>] set_track mm/kasan/kasan.c:524 [inline]
       [<ffffffff8147e849>] kasan_kmalloc.part.1+0xc9/0xf0 mm/kasan/kasan.c:616
       [<ffffffff8147ea5f>] kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:601
       [<ffffffff8147f022>] kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:554
       [<ffffffff8147a72c>] slab_post_alloc_hook mm/slub.c:1349 [inline]
       [<ffffffff8147a72c>] slab_alloc_node mm/slub.c:2615 [inline]
       [<ffffffff8147a72c>] slab_alloc mm/slub.c:2623 [inline]
       [<ffffffff8147a72c>] kmem_cache_alloc+0xdc/0x2c0 mm/slub.c:2628
       [<ffffffff823a1c2d>] inet_getpeer+0x159d/0x1d70 net/ipv4/inetpeer.c:444
       [<ffffffff82610027>] inet_getpeer_v6 include/net/inetpeer.h:127 [inline]
       [<ffffffff82610027>] icmpv6_xrlim_allow net/ipv6/icmp.c:211 [inline]
       [<ffffffff82610027>] icmp6_send+0x17b7/0x1b70 net/ipv6/icmp.c:491
       [<ffffffff826117e9>] icmpv6_param_prob+0x29/0x40 net/ipv6/icmp.c:551
       [<ffffffff8262ccc6>] ip6_frag_queue net/ipv6/reassembly.c:263 [inline]
       [<ffffffff8262ccc6>] ipv6_frag_rcv+0x3de6/0x4f80 net/ipv6/reassembly.c:562
       [<ffffffff825a0a9d>] ip6_input_finish+0x57d/0x1510 net/ipv6/ip6_input.c:248
       [<ffffffff825a3836>] NF_HOOK_THRESH include/linux/netfilter.h:226 [inline]
       [<ffffffff825a3836>] NF_HOOK include/linux/netfilter.h:249 [inline]
       [<ffffffff825a3836>] ip6_input+0xf6/0x200 net/ipv6/ip6_input.c:280
       [<ffffffff8259fffe>] dst_input include/net/dst.h:504 [inline]
       [<ffffffff8259fffe>] ip6_rcv_finish+0x14e/0x670 net/ipv6/ip6_input.c:62
       [<ffffffff825a2ae2>] NF_HOOK_THRESH include/linux/netfilter.h:226 [inline]
       [<ffffffff825a2ae2>] NF_HOOK include/linux/netfilter.h:249 [inline]
       [<ffffffff825a2ae2>] ipv6_rcv+0x10b2/0x1d10 net/ipv6/ip6_input.c:186
       [<ffffffff8221b6b8>] __netif_receive_skb_core+0x12c8/0x2820 net/core/dev.c:4019
       [<ffffffff82223d6b>] __netif_receive_skb+0x5b/0x1c0 net/core/dev.c:4054
       [<ffffffff8222b10a>] process_backlog+0x20a/0x670 net/core/dev.c:4647
       [<ffffffff8222a517>] napi_poll net/core/dev.c:4885 [inline]
       [<ffffffff8222a517>] net_rx_action+0x367/0xd50 net/core/dev.c:4950
       [<ffffffff82708b9c>] __do_softirq+0x22c/0xa1a kernel/softirq.c:273
       [<ffffffff82706d9c>] do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:929
       [<ffffffff810e1ca4>] do_softirq.part.2+0x54/0x60 kernel/softirq.c:317
       [<ffffffff810e1df9>] do_softirq+0x19/0x20 kernel/softirq.c:320
       [<ffffffff82219d1c>] netif_rx_ni+0xec/0x3a0 net/core/dev.c:3653
       [<ffffffff81e0f07a>] tun_get_user+0xf3a/0x2690 drivers/net/tun.c:1264
       [<ffffffff81e109e5>] tun_chr_write_iter+0xd5/0x190 drivers/net/tun.c:1283
       [<ffffffff81491dd3>] do_iter_readv_writev+0x133/0x1d0 fs/read_write.c:664
       [<ffffffff81493105>] do_readv_writev+0x335/0x6f0 fs/read_write.c:808
       [<ffffffff814935eb>] vfs_writev+0x7b/0xb0 fs/read_write.c:847
       [<ffffffff81495ac9>] SYSC_writev fs/read_write.c:880 [inline]
       [<ffffffff81495ac9>] SyS_writev+0xd9/0x250 fs/read_write.c:872
       [<ffffffff82705ca1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff811ff31c>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff811ff31c>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff811ff31c>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff811ff31c>] __lock_acquire+0x3e6c/0x5f10 kernel/locking/lockdep.c:3213
       [<ffffffff81202efe>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82704dd6>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
       [<ffffffff82704dd6>] _raw_spin_lock+0x36/0x50 kernel/locking/spinlock.c:151
       [<ffffffff823a76cb>] spin_lock include/linux/spinlock.h:302 [inline]
       [<ffffffff823a76cb>] ip_defrag+0x31b/0x40c0 net/ipv4/ip_fragment.c:680
       [<ffffffff823ab817>] ip_check_defrag+0x3a7/0x710 net/ipv4/ip_fragment.c:724
       [<ffffffff826cdfea>] packet_rcv_fanout+0x52a/0x5e0 net/packet/af_packet.c:1458
       [<ffffffff82230210>] dev_queue_xmit_nit net/core/dev.c:1913 [inline]
       [<ffffffff82230210>] xmit_one net/core/dev.c:2755 [inline]
       [<ffffffff82230210>] dev_hard_start_xmit+0x650/0x11c0 net/core/dev.c:2775
       [<ffffffff8229dc48>] sch_direct_xmit+0x2b8/0x6c0 net/sched/sch_generic.c:165
       [<ffffffff82231fd5>] __dev_xmit_skb net/core/dev.c:2957 [inline]
       [<ffffffff82231fd5>] __dev_queue_xmit+0xf95/0x1c30 net/core/dev.c:3175
       [<ffffffff82232c87>] dev_queue_xmit+0x17/0x20 net/core/dev.c:3241
       [<ffffffff82253150>] neigh_resolve_output+0x600/0x780 net/core/neighbour.c:1329
       [<ffffffff823b3170>] dst_neigh_output include/net/dst.h:461 [inline]
       [<ffffffff823b3170>] ip_finish_output2+0x8f0/0x1100 net/ipv4/ip_output.c:213
       [<ffffffff823b59f0>] ip_do_fragment+0x1870/0x1f60 net/ipv4/ip_output.c:635
       [<ffffffff823b96c5>] ip_fragment.constprop.5+0x145/0x200 net/ipv4/ip_output.c:505
       [<ffffffff823b9b16>] ip_finish_output+0x396/0xc00 net/ipv4/ip_output.c:286
       [<ffffffff823bd297>] NF_HOOK_COND include/linux/netfilter.h:240 [inline]
       [<ffffffff823bd297>] ip_mc_output+0x237/0x980 net/ipv4/ip_output.c:347
       [<ffffffff823bab1b>] dst_output include/net/dst.h:498 [inline]
       [<ffffffff823bab1b>] ip_local_out+0x9b/0x180 net/ipv4/ip_output.c:119
       [<ffffffff823c083c>] ip_send_skb+0x3c/0xc0 net/ipv4/ip_output.c:1453
       [<ffffffff824662a3>] udp_send_skb+0x503/0xc70 net/ipv4/udp.c:842
       [<ffffffff8246d129>] udp_sendmsg+0x16c9/0x1c70 net/ipv4/udp.c:1072
       [<ffffffff824963c3>] inet_sendmsg+0x203/0x4d0 net/ipv4/af_inet.c:755
       [<ffffffff821c2ebb>] sock_sendmsg_nosec net/socket.c:638 [inline]
       [<ffffffff821c2ebb>] sock_sendmsg+0xbb/0x110 net/socket.c:648
       [<ffffffff821c70e0>] SYSC_sendto net/socket.c:1678 [inline]
       [<ffffffff821c70e0>] SyS_sendto+0x220/0x370 net/socket.c:1646
       [<ffffffff82705ca1>] 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 ***

4 locks held by syz-executor265/2077:
 #0:  (rcu_read_lock_bh){......}, at: [<ffffffff823b2a8b>] ip_finish_output2+0x20b/0x1100 net/ipv4/ip_output.c:193
 #1:  (rcu_read_lock_bh){......}, at: [<ffffffff82231217>] __dev_queue_xmit+0x1d7/0x1c30 net/core/dev.c:3139
 #2:  (_xmit_NETROM){+.-...}, at: [<ffffffff8229dbc3>] spin_lock include/linux/spinlock.h:302 [inline]
 #2:  (_xmit_NETROM){+.-...}, at: [<ffffffff8229dbc3>] __netif_tx_lock include/linux/netdevice.h:3299 [inline]
 #2:  (_xmit_NETROM){+.-...}, at: [<ffffffff8229dbc3>] sch_direct_xmit+0x233/0x6c0 net/sched/sch_generic.c:163
 #3:  (rcu_read_lock){......}, at: [<ffffffff8222fc68>] xmit_one net/core/dev.c:2754 [inline]
 #3:  (rcu_read_lock){......}, at: [<ffffffff8222fc68>] dev_hard_start_xmit+0xa8/0x11c0 net/core/dev.c:2775

stack backtrace:
CPU: 1 PID: 2077 Comm: syz-executor265 Not tainted 4.4.159+ #108
 0000000000000000 b39aeeed83d339d1 ffff8800b648ed88 ffffffff81a994bd
 ffffffff83accfd0 ffffffff83acd690 ffffffff83accfd0 ffff8800b70c20f8
 ffff8800b70c17c0 ffff8800b648edd0 ffffffff813a84ea 0000000000000003
Call Trace:
 [<ffffffff81a994bd>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81a994bd>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff813a84ea>] print_circular_bug.cold.34+0x2f7/0x432 kernel/locking/lockdep.c:1226
 [<ffffffff811ff31c>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff811ff31c>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff811ff31c>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff811ff31c>] __lock_acquire+0x3e6c/0x5f10 kernel/locking/lockdep.c:3213
 [<ffffffff81202efe>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff82704dd6>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
 [<ffffffff82704dd6>] _raw_spin_lock+0x36/0x50 kernel/locking/spinlock.c:151
 [<ffffffff823a76cb>] spin_lock include/linux/spinlock.h:302 [inline]
 [<ffffffff823a76cb>] ip_defrag+0x31b/0x40c0 net/ipv4/ip_fragment.c:680
 [<ffffffff823ab817>] ip_check_defrag+0x3a7/0x710 net/ipv4/ip_fragment.c:724
 [<ffffffff826cdfea>] packet_rcv_fanout+0x52a/0x5e0 net/packet/af_packet.c:1458
 [<ffffffff82230210>] dev_queue_xmit_nit net/core/dev.c:1913 [inline]
 [<ffffffff82230210>] xmit_one net/core/dev.c:2755 [inline]
 [<ffffffff82230210>] dev_hard_start_xmit+0x650/0x11c0 net/core/dev.c:2775
 [<ffffffff8229dc48>] sch_direct_xmit+0x2b8/0x6c0 net/sched/sch_generic.c:165
 [<ffffffff82231fd5>] __dev_xmit_skb net/core/dev.c:2957 [inline]
 [<ffffffff82231fd5>] __dev_queue_xmit+0xf95/0x1c30 net/core/dev.c:3175
 [<ffffffff82232c87>] dev_queue_xmit+0x17/0x20 net/core/dev.c:3241
 [<ffffffff82253150>] neigh_resolve_output+0x600/0x780 net/core/neighbour.c:1329
 [<ffffffff823b3170>] dst_neigh_output include/net/dst.h:461 [inline]
 [<ffffffff823b3170>] ip_finish_output2+0x8f0/0x1100 net/ipv4/ip_output.c:213
 [<ffffffff823b59f0>] ip_do_fragment+0x1870/0x1f60 net/ipv4/ip_output.c:635
 [<ffffffff823b96c5>] ip_fragment.constprop.5+0x145/0x200 net/ipv4/ip_output.c:505
 [<ffffffff823b9b16>] ip_finish_output+0x396/0xc00 net/ipv4/ip_output.c:286
 [<ffffffff823bd297>] NF_HOOK_COND include/linux/netfilter.h:240 [inline]
 [<ffffffff823bd297>] ip_mc_output+0x237/0x980 net/ipv4/ip_output.c:347
 [<ffffffff823bab1b>] dst_output include/net/dst.h:498 [inline]
 [<ffffffff823bab1b>] ip_local_out+0x9b/0x180 net/ipv4/ip_output.c:119
 [<ffffffff823c083c>] ip_send_skb+0x3c/0xc0 net/ipv4/ip_output.c:1453
 [<ffffffff824662a3>] udp_send_skb+0x503/0xc70 net/ipv4/udp.c:842
 [<ffffffff8246d129>] udp_sendmsg+0x16c9/0x1c70 net/ipv4/udp.c:1072
 [<ffffffff824963c3>] inet_sendmsg+0x203/0x4d0 net/ipv4/af_inet.c:755
 [<ffffffff821c2ebb>] sock_sendmsg_nosec net/socket.c:638 [inline]
 [<ffffffff821c2ebb>] sock_sendmsg+0xbb/0x110 net/socket.c:648
 [<ffffffff821c70e0>] SYSC_sendto net/socket.c:1678 [inline]
 [<ffffffff821c70e0>] SyS_sendto+0x220/0x370 net/socket.c:1646
 [<ffffffff82705ca1>] entry_SYSCALL_64_fastpath+0x1e/0x9a