======================================================
[ INFO: possible circular locking dependency detected ]
4.4.162+ #7 Not tainted
-------------------------------------------------------
syz-executor119/2085 is trying to acquire lock:
 (&(&q->lock)->rlock){+.-...}, at: [<ffffffff823a80ab>] spin_lock include/linux/spinlock.h:302 [inline]
 (&(&q->lock)->rlock){+.-...}, at: [<ffffffff823a80ab>] ip_defrag+0x31b/0x40c0 net/ipv4/ip_fragment.c:680

but task is already holding lock:
 (_xmit_NETROM){+.-...}, at: [<ffffffff8229e5a3>] spin_lock include/linux/spinlock.h:302 [inline]
 (_xmit_NETROM){+.-...}, at: [<ffffffff8229e5a3>] __netif_tx_lock include/linux/netdevice.h:3306 [inline]
 (_xmit_NETROM){+.-...}, at: [<ffffffff8229e5a3>] 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:

       [<ffffffff81202cde>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff827055de>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:112 [inline]
       [<ffffffff827055de>] _raw_spin_lock_irqsave+0x4e/0x70 kernel/locking/spinlock.c:159
       [<ffffffff81b34a6b>] depot_save_stack+0x20b/0x5eb lib/stackdepot.c:252
       [<ffffffff8147e6a9>] save_stack mm/kasan/kasan.c:518 [inline]
       [<ffffffff8147e6a9>] set_track mm/kasan/kasan.c:524 [inline]
       [<ffffffff8147e6a9>] kasan_kmalloc.part.1+0xc9/0xf0 mm/kasan/kasan.c:616
       [<ffffffff8147e8bf>] kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:601
       [<ffffffff8147ee82>] kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:554
       [<ffffffff8147a58c>] slab_post_alloc_hook mm/slub.c:1349 [inline]
       [<ffffffff8147a58c>] slab_alloc_node mm/slub.c:2615 [inline]
       [<ffffffff8147a58c>] slab_alloc mm/slub.c:2623 [inline]
       [<ffffffff8147a58c>] kmem_cache_alloc+0xdc/0x2c0 mm/slub.c:2628
       [<ffffffff823a260d>] inet_getpeer+0x159d/0x1d70 net/ipv4/inetpeer.c:444
       [<ffffffff82610457>] inet_getpeer_v6 include/net/inetpeer.h:127 [inline]
       [<ffffffff82610457>] icmpv6_xrlim_allow net/ipv6/icmp.c:211 [inline]
       [<ffffffff82610457>] icmp6_send+0x17b7/0x1b70 net/ipv6/icmp.c:491
       [<ffffffff82611c19>] icmpv6_param_prob+0x29/0x40 net/ipv6/icmp.c:551
       [<ffffffff8262ceb5>] ip6_frag_queue net/ipv6/reassembly.c:228 [inline]
       [<ffffffff8262ceb5>] ipv6_frag_rcv+0x3ba5/0x4f80 net/ipv6/reassembly.c:562
       [<ffffffff825a0f1d>] ip6_input_finish+0x57d/0x1510 net/ipv6/ip6_input.c:248
       [<ffffffff825a3cb6>] NF_HOOK_THRESH include/linux/netfilter.h:226 [inline]
       [<ffffffff825a3cb6>] NF_HOOK include/linux/netfilter.h:249 [inline]
       [<ffffffff825a3cb6>] ip6_input+0xf6/0x200 net/ipv6/ip6_input.c:280
       [<ffffffff825a047e>] dst_input include/net/dst.h:504 [inline]
       [<ffffffff825a047e>] ip6_rcv_finish+0x14e/0x670 net/ipv6/ip6_input.c:62
       [<ffffffff82680a7b>] NF_HOOK_THRESH include/linux/netfilter.h:226 [inline]
       [<ffffffff82680a7b>] ipv6_defrag+0x33b/0x5c0 net/ipv6/netfilter/nf_defrag_ipv6_hooks.c:78
       [<ffffffff822e52f2>] nf_iterate+0x182/0x210 net/netfilter/core.c:274
       [<ffffffff822e5536>] nf_hook_slow+0x1b6/0x340 net/netfilter/core.c:306
       [<ffffffff825a3305>] nf_hook_thresh include/linux/netfilter.h:187 [inline]
       [<ffffffff825a3305>] NF_HOOK_THRESH include/linux/netfilter.h:224 [inline]
       [<ffffffff825a3305>] NF_HOOK include/linux/netfilter.h:249 [inline]
       [<ffffffff825a3305>] ipv6_rcv+0x1455/0x1d10 net/ipv6/ip6_input.c:186
       [<ffffffff8221c078>] __netif_receive_skb_core+0x12c8/0x2820 net/core/dev.c:4041
       [<ffffffff8222472b>] __netif_receive_skb+0x5b/0x1c0 net/core/dev.c:4076
       [<ffffffff8222baca>] process_backlog+0x20a/0x670 net/core/dev.c:4669
       [<ffffffff8222aed7>] napi_poll net/core/dev.c:4907 [inline]
       [<ffffffff8222aed7>] net_rx_action+0x367/0xd50 net/core/dev.c:4972
       [<ffffffff827091dc>] __do_softirq+0x22c/0xa1a kernel/softirq.c:273
       [<ffffffff810e1dbd>] invoke_softirq kernel/softirq.c:350 [inline]
       [<ffffffff810e1dbd>] irq_exit+0x10d/0x140 kernel/softirq.c:391
       [<ffffffff8270880d>] exiting_irq arch/x86/include/asm/apic.h:652 [inline]
       [<ffffffff8270880d>] do_IRQ+0x10d/0x1c0 arch/x86/kernel/irq.c:251
       [<ffffffff82706e1d>] ret_from_intr+0x0/0x20
       [<ffffffff82217e7b>] netif_rx_internal+0x15b/0x700 net/core/dev.c:3637
       [<ffffffff8221a695>] netif_rx_ni+0xa5/0x3a0 net/core/dev.c:3673
       [<ffffffff81e0f53a>] tun_get_user+0xf3a/0x2690 drivers/net/tun.c:1264
       [<ffffffff81e10ea5>] tun_chr_write_iter+0xd5/0x190 drivers/net/tun.c:1283
       [<ffffffff81491c33>] do_iter_readv_writev+0x133/0x1d0 fs/read_write.c:664
       [<ffffffff814937b7>] compat_do_readv_writev+0x337/0x6f0 fs/read_write.c:982
       [<ffffffff81493f11>] compat_writev+0xe1/0x150 fs/read_write.c:1090
       [<ffffffff81496228>] C_SYSC_writev fs/read_write.c:1110 [inline]
       [<ffffffff81496228>] compat_SyS_writev+0xd8/0x1c0 fs/read_write.c:1099
       [<ffffffff8100629e>] do_syscall_32_irqs_on arch/x86/entry/common.c:396 [inline]
       [<ffffffff8100629e>] do_fast_syscall_32+0x31e/0xa80 arch/x86/entry/common.c:463
       [<ffffffff82707a50>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff811ff0fc>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff811ff0fc>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff811ff0fc>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff811ff0fc>] __lock_acquire+0x3e6c/0x5f10 kernel/locking/lockdep.c:3213
       [<ffffffff81202cde>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82705426>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
       [<ffffffff82705426>] _raw_spin_lock+0x36/0x50 kernel/locking/spinlock.c:151
       [<ffffffff823a80ab>] spin_lock include/linux/spinlock.h:302 [inline]
       [<ffffffff823a80ab>] ip_defrag+0x31b/0x40c0 net/ipv4/ip_fragment.c:680
       [<ffffffff823ac1f7>] ip_check_defrag+0x3a7/0x710 net/ipv4/ip_fragment.c:724
       [<ffffffff826ce6aa>] packet_rcv_fanout+0x52a/0x5e0 net/packet/af_packet.c:1458
       [<ffffffff82230bd0>] dev_queue_xmit_nit net/core/dev.c:1935 [inline]
       [<ffffffff82230bd0>] xmit_one net/core/dev.c:2777 [inline]
       [<ffffffff82230bd0>] dev_hard_start_xmit+0x650/0x11c0 net/core/dev.c:2797
       [<ffffffff8229e628>] sch_direct_xmit+0x2b8/0x6c0 net/sched/sch_generic.c:165
       [<ffffffff82232995>] __dev_xmit_skb net/core/dev.c:2979 [inline]
       [<ffffffff82232995>] __dev_queue_xmit+0xf95/0x1c30 net/core/dev.c:3197
       [<ffffffff82233647>] dev_queue_xmit+0x17/0x20 net/core/dev.c:3263
       [<ffffffff82253b10>] neigh_resolve_output+0x600/0x780 net/core/neighbour.c:1329
       [<ffffffff823b3b50>] dst_neigh_output include/net/dst.h:461 [inline]
       [<ffffffff823b3b50>] ip_finish_output2+0x8f0/0x1100 net/ipv4/ip_output.c:213
       [<ffffffff823b63d0>] ip_do_fragment+0x1870/0x1f60 net/ipv4/ip_output.c:635
       [<ffffffff823ba0a5>] ip_fragment.constprop.5+0x145/0x200 net/ipv4/ip_output.c:505
       [<ffffffff823ba4f6>] ip_finish_output+0x396/0xc00 net/ipv4/ip_output.c:286
       [<ffffffff823bdc77>] NF_HOOK_COND include/linux/netfilter.h:240 [inline]
       [<ffffffff823bdc77>] ip_mc_output+0x237/0x980 net/ipv4/ip_output.c:347
       [<ffffffff823bb4fb>] dst_output include/net/dst.h:498 [inline]
       [<ffffffff823bb4fb>] ip_local_out+0x9b/0x180 net/ipv4/ip_output.c:119
       [<ffffffff823c121c>] ip_send_skb+0x3c/0xc0 net/ipv4/ip_output.c:1453
       [<ffffffff82466373>] udp_send_skb+0x503/0xc70 net/ipv4/udp.c:842
       [<ffffffff8246d1f9>] udp_sendmsg+0x16c9/0x1c70 net/ipv4/udp.c:1072
       [<ffffffff82496493>] inet_sendmsg+0x203/0x4d0 net/ipv4/af_inet.c:755
       [<ffffffff821c376b>] sock_sendmsg_nosec net/socket.c:638 [inline]
       [<ffffffff821c376b>] sock_sendmsg+0xbb/0x110 net/socket.c:648
       [<ffffffff821c7990>] SYSC_sendto net/socket.c:1678 [inline]
       [<ffffffff821c7990>] SyS_sendto+0x220/0x370 net/socket.c:1646
       [<ffffffff8100629e>] do_syscall_32_irqs_on arch/x86/entry/common.c:396 [inline]
       [<ffffffff8100629e>] do_fast_syscall_32+0x31e/0xa80 arch/x86/entry/common.c:463
       [<ffffffff82707a50>] 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-executor119/2085:
 #0:  (rcu_read_lock_bh){......}, at: [<ffffffff823b346b>] ip_finish_output2+0x20b/0x1100 net/ipv4/ip_output.c:193
 #1:  (rcu_read_lock_bh){......}, at: [<ffffffff82231bd7>] __dev_queue_xmit+0x1d7/0x1c30 net/core/dev.c:3161
 #2:  (_xmit_NETROM){+.-...}, at: [<ffffffff8229e5a3>] spin_lock include/linux/spinlock.h:302 [inline]
 #2:  (_xmit_NETROM){+.-...}, at: [<ffffffff8229e5a3>] __netif_tx_lock include/linux/netdevice.h:3306 [inline]
 #2:  (_xmit_NETROM){+.-...}, at: [<ffffffff8229e5a3>] sch_direct_xmit+0x233/0x6c0 net/sched/sch_generic.c:163
 #3:  (rcu_read_lock){......}, at: [<ffffffff82230628>] xmit_one net/core/dev.c:2776 [inline]
 #3:  (rcu_read_lock){......}, at: [<ffffffff82230628>] dev_hard_start_xmit+0xa8/0x11c0 net/core/dev.c:2797

stack backtrace:
CPU: 1 PID: 2085 Comm: syz-executor119 Not tainted 4.4.162+ #7
 0000000000000000 58a7002b0ad2e19a ffff8801d3f86d18 ffffffff81a994bd
 ffffffff83acb680 ffffffff83acbd40 ffffffff83acb680 ffff8801d5df38b8
 ffff8801d5df2f80 ffff8801d3f86d60 ffffffff813a834a 0000000000000003
Call Trace:
 [<ffffffff81a994bd>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81a994bd>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff813a834a>] print_circular_bug.cold.34+0x2f7/0x432 kernel/locking/lockdep.c:1226
 [<ffffffff811ff0fc>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff811ff0fc>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff811ff0fc>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff811ff0fc>] __lock_acquire+0x3e6c/0x5f10 kernel/locking/lockdep.c:3213
 [<ffffffff81202cde>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff82705426>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
 [<ffffffff82705426>] _raw_spin_lock+0x36/0x50 kernel/locking/spinlock.c:151
 [<ffffffff823a80ab>] spin_lock include/linux/spinlock.h:302 [inline]
 [<ffffffff823a80ab>] ip_defrag+0x31b/0x40c0 net/ipv4/ip_fragment.c:680
 [<ffffffff823ac1f7>] ip_check_defrag+0x3a7/0x710 net/ipv4/ip_fragment.c:724
 [<ffffffff826ce6aa>] packet_rcv_fanout+0x52a/0x5e0 net/packet/af_packet.c:1458
 [<ffffffff82230bd0>] dev_queue_xmit_nit net/core/dev.c:1935 [inline]
 [<ffffffff82230bd0>] xmit_one net/core/dev.c:2777 [inline]
 [<ffffffff82230bd0>] dev_hard_start_xmit+0x650/0x11c0 net/core/dev.c:2797
 [<ffffffff8229e628>] sch_direct_xmit+0x2b8/0x6c0 net/sched/sch_generic.c:165
 [<ffffffff82232995>] __dev_xmit_skb net/core/dev.c:2979 [inline]
 [<ffffffff82232995>] __dev_queue_xmit+0xf95/0x1c30 net/core/dev.c:3197
 [<ffffffff82233647>] dev_queue_xmit+0x17/0x20 net/core/dev.c:3263
 [<ffffffff82253b10>] neigh_resolve_output+0x600/0x780 net/core/neighbour.c:1329
 [<ffffffff823b3b50>] dst_neigh_output include/net/dst.h:461 [inline]
 [<ffffffff823b3b50>] ip_finish_output2+0x8f0/0x1100 net/ipv4/ip_output.c:213
 [<ffffffff823b63d0>] ip_do_fragment+0x1870/0x1f60 net/ipv4/ip_output.c:635
 [<ffffffff823ba0a5>] ip_fragment.constprop.5+0x145/0x200 net/ipv4/ip_output.c:505
 [<ffffffff823ba4f6>] ip_finish_output+0x396/0xc00 net/ipv4/ip_output.c:286
 [<ffffffff823bdc77>] NF_HOOK_COND include/linux/netfilter.h:240 [inline]
 [<ffffffff823bdc77>] ip_mc_output+0x237/0x980 net/ipv4/ip_output.c:347
 [<ffffffff823bb4fb>] dst_output include/net/dst.h:498 [inline]
 [<ffffffff823bb4fb>] ip_local_out+0x9b/0x180 net/ipv4/ip_output.c:119
 [<ffffffff823c121c>] ip_send_skb+0x3c/0xc0 net/ipv4/ip_output.c:1453
 [<ffffffff82466373>] udp_send_skb+0x503/0xc70 net/ipv4/udp.c:842
 [<ffffffff8246d1f9>] udp_sendmsg+0x16c9/0x1c70 net/ipv4/udp.c:1072
 [<ffffffff82496493>] inet_sendmsg+0x203/0x4d0 net/ipv4/af_inet.c:755
 [<ffffffff821c376b>] sock_sendmsg_nosec net/socket.c:638 [inline]
 [<ffffffff821c376b>] sock_sendmsg+0xbb/0x110 net/socket.c:648
 [<ffffffff821c7990>] SYSC_sendto net/socket.c:1678 [inline]
 [<ffffffff821c7990>] SyS_sendto+0x220/0x370 net/socket.c:1646
 [<ffffffff8100629e>] do_syscall_32_irqs_on arch/x86/entry/common.c:396 [inline]
 [<ffffffff8100629e>] do_fast_syscall_32+0x31e/0xa80 arch/x86/entry/common.c:463
 [<ffffffff82707a50>] sysenter_flags_fixed+0xd/0x1a