====================================================== [ INFO: possible circular locking dependency detected ] 4.4.162+ #118 Not tainted ------------------------------------------------------- syz-executor383/2076 is trying to acquire lock: (_xmit_NETROM){+.-...}, at: [] spin_lock include/linux/spinlock.h:302 [inline] (_xmit_NETROM){+.-...}, at: [] __netif_tx_lock include/linux/netdevice.h:3306 [inline] (_xmit_NETROM){+.-...}, at: [] sch_direct_xmit+0x233/0x6c0 net/sched/sch_generic.c:163 but task is already holding lock: (&(&q->lock)->rlock){+.-...}, at: [] spin_lock include/linux/spinlock.h:302 [inline] (&(&q->lock)->rlock){+.-...}, at: [] ipv6_frag_rcv+0x5eb/0x4f80 net/ipv6/reassembly.c:560 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: [] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592 [] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:112 [inline] [] _raw_spin_lock_irqsave+0x4e/0x70 kernel/locking/spinlock.c:159 [] lock_timer_base+0xd5/0x170 kernel/time/timer.c:779 [] __mod_timer kernel/time/timer.c:799 [inline] [] mod_timer+0x1af/0x8f0 kernel/time/timer.c:925 [] inet_frag_intern net/ipv4/inet_fragment.c:350 [inline] [] inet_frag_create net/ipv4/inet_fragment.c:392 [inline] [] inet_frag_find+0x73e/0x9a0 net/ipv4/inet_fragment.c:426 [] ip_find net/ipv4/ip_fragment.c:275 [inline] [] ip_defrag+0x2f0/0x40c0 net/ipv4/ip_fragment.c:676 [] ip_check_defrag+0x3a7/0x710 net/ipv4/ip_fragment.c:724 [] packet_rcv_fanout+0x52a/0x5e0 net/packet/af_packet.c:1458 [] dev_queue_xmit_nit net/core/dev.c:1935 [inline] [] xmit_one net/core/dev.c:2777 [inline] [] dev_hard_start_xmit+0x650/0x11c0 net/core/dev.c:2797 [] sch_direct_xmit+0x2b8/0x6c0 net/sched/sch_generic.c:165 [] __dev_xmit_skb net/core/dev.c:2979 [inline] [] __dev_queue_xmit+0xf95/0x1c30 net/core/dev.c:3197 [] dev_queue_xmit+0x17/0x20 net/core/dev.c:3263 [] neigh_resolve_output+0x600/0x780 net/core/neighbour.c:1329 [] dst_neigh_output include/net/dst.h:461 [inline] [] ip_finish_output2+0x8f0/0x1100 net/ipv4/ip_output.c:213 [] ip_do_fragment+0x1870/0x1f60 net/ipv4/ip_output.c:635 [] ip_fragment.constprop.5+0x145/0x200 net/ipv4/ip_output.c:505 [] ip_finish_output+0x396/0xc00 net/ipv4/ip_output.c:286 [] NF_HOOK_COND include/linux/netfilter.h:240 [inline] [] ip_mc_output+0x237/0x980 net/ipv4/ip_output.c:347 [] dst_output include/net/dst.h:498 [inline] [] ip_local_out+0x9b/0x180 net/ipv4/ip_output.c:119 [] ip_send_skb+0x3c/0xc0 net/ipv4/ip_output.c:1453 [] udp_send_skb+0x503/0xc70 net/ipv4/udp.c:842 [] udp_sendmsg+0x16c9/0x1c70 net/ipv4/udp.c:1072 [] inet_sendmsg+0x203/0x4d0 net/ipv4/af_inet.c:755 [] sock_sendmsg_nosec net/socket.c:638 [inline] [] sock_sendmsg+0xbb/0x110 net/socket.c:648 [] SYSC_sendto net/socket.c:1678 [inline] [] SyS_sendto+0x220/0x370 net/socket.c:1646 [] entry_SYSCALL_64_fastpath+0x1e/0x9a [] check_prev_add kernel/locking/lockdep.c:1853 [inline] [] check_prevs_add kernel/locking/lockdep.c:1958 [inline] [] validate_chain kernel/locking/lockdep.c:2144 [inline] [] __lock_acquire+0x3e6c/0x5f10 kernel/locking/lockdep.c:3213 [] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592 [] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline] [] _raw_spin_lock+0x36/0x50 kernel/locking/spinlock.c:151 [] spin_lock include/linux/spinlock.h:302 [inline] [] __netif_tx_lock include/linux/netdevice.h:3306 [inline] [] sch_direct_xmit+0x233/0x6c0 net/sched/sch_generic.c:163 [] __dev_xmit_skb net/core/dev.c:2979 [inline] [] __dev_queue_xmit+0xf95/0x1c30 net/core/dev.c:3197 [] dev_queue_xmit+0x17/0x20 net/core/dev.c:3263 [] neigh_resolve_output+0x600/0x780 net/core/neighbour.c:1329 [] dst_neigh_output include/net/dst.h:461 [inline] [] ip6_finish_output2+0xb94/0x1ca0 net/ipv6/ip6_output.c:113 [] ip6_finish_output+0x2ee/0x750 net/ipv6/ip6_output.c:131 [] NF_HOOK_COND include/linux/netfilter.h:240 [inline] [] ip6_output+0x1af/0x520 net/ipv6/ip6_output.c:145 [] dst_output include/net/dst.h:498 [inline] [] NF_HOOK_THRESH include/linux/netfilter.h:226 [inline] [] NF_HOOK include/linux/netfilter.h:249 [inline] [] ndisc_send_skb+0x972/0x10e0 net/ipv6/ndisc.c:471 [] ndisc_send_ns+0x4fb/0x6f0 net/ipv6/ndisc.c:595 [] ndisc_solicit+0x2a0/0x420 net/ipv6/ndisc.c:686 [] neigh_probe+0xca/0x100 net/core/neighbour.c:871 [] __neigh_event_send+0x2a0/0xc30 net/core/neighbour.c:1027 [] neigh_event_send include/net/neighbour.h:431 [inline] [] neigh_resolve_output+0x629/0x780 net/core/neighbour.c:1313 [] dst_neigh_output include/net/dst.h:461 [inline] [] ip6_finish_output2+0xb94/0x1ca0 net/ipv6/ip6_output.c:113 [] ip6_finish_output+0x2ee/0x750 net/ipv6/ip6_output.c:131 [] NF_HOOK_COND include/linux/netfilter.h:240 [inline] [] ip6_output+0x1af/0x520 net/ipv6/ip6_output.c:145 [] dst_output include/net/dst.h:498 [inline] [] ip6_local_out+0x9b/0x180 net/ipv6/output_core.c:169 [] ip6_send_skb+0xa1/0x340 net/ipv6/ip6_output.c:1725 [] ip6_push_pending_frames+0xb3/0xe0 net/ipv6/ip6_output.c:1745 [] icmpv6_push_pending_frames+0x335/0x530 net/ipv6/icmp.c:276 [] icmp6_send+0x15f3/0x1b70 net/ipv6/icmp.c:537 [] icmpv6_param_prob+0x29/0x40 net/ipv6/icmp.c:551 [] ip6_frag_queue net/ipv6/reassembly.c:228 [inline] [] ipv6_frag_rcv+0x3ba5/0x4f80 net/ipv6/reassembly.c:562 [] ip6_input_finish+0x57d/0x1510 net/ipv6/ip6_input.c:248 [] NF_HOOK_THRESH include/linux/netfilter.h:226 [inline] [] NF_HOOK include/linux/netfilter.h:249 [inline] [] ip6_input+0xf6/0x200 net/ipv6/ip6_input.c:280 [] dst_input include/net/dst.h:504 [inline] [] ip6_rcv_finish+0x14e/0x670 net/ipv6/ip6_input.c:62 [] NF_HOOK_THRESH include/linux/netfilter.h:226 [inline] [] ipv6_defrag+0x33b/0x5c0 net/ipv6/netfilter/nf_defrag_ipv6_hooks.c:78 [] nf_iterate+0x182/0x210 net/netfilter/core.c:274 [] nf_hook_slow+0x1b6/0x340 net/netfilter/core.c:306 [] nf_hook_thresh include/linux/netfilter.h:187 [inline] [] NF_HOOK_THRESH include/linux/netfilter.h:224 [inline] [] NF_HOOK include/linux/netfilter.h:249 [inline] [] ipv6_rcv+0x1455/0x1d10 net/ipv6/ip6_input.c:186 [] __netif_receive_skb_core+0x12c8/0x2820 net/core/dev.c:4041 [] __netif_receive_skb+0x5b/0x1c0 net/core/dev.c:4076 [] process_backlog+0x20a/0x670 net/core/dev.c:4669 [] napi_poll net/core/dev.c:4907 [inline] [] net_rx_action+0x367/0xd50 net/core/dev.c:4972 [] __do_softirq+0x22c/0xa1a kernel/softirq.c:273 [] do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:929 [] do_softirq.part.2+0x54/0x60 kernel/softirq.c:317 [] do_softirq+0x19/0x20 kernel/softirq.c:320 [] netif_rx_ni+0xec/0x3a0 net/core/dev.c:3675 [] tun_get_user+0xf3a/0x2690 drivers/net/tun.c:1264 [] tun_chr_write_iter+0xd5/0x190 drivers/net/tun.c:1283 [] do_iter_readv_writev+0x133/0x1d0 fs/read_write.c:664 [] do_readv_writev+0x335/0x6f0 fs/read_write.c:808 [] vfs_writev+0x7b/0xb0 fs/read_write.c:847 [] SYSC_writev fs/read_write.c:880 [inline] [] SyS_writev+0xd9/0x250 fs/read_write.c:872 [] entry_SYSCALL_64_fastpath+0x1e/0x9a other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&(&q->lock)->rlock); lock(_xmit_NETROM); lock(&(&q->lock)->rlock); lock(_xmit_NETROM); *** DEADLOCK *** 10 locks held by syz-executor383/2076: #0: (rcu_read_lock){......}, at: [] __skb_unlink include/linux/skbuff.h:1643 [inline] #0: (rcu_read_lock){......}, at: [] __skb_dequeue include/linux/skbuff.h:1659 [inline] #0: (rcu_read_lock){......}, at: [] process_backlog+0x1a6/0x670 net/core/dev.c:4666 #1: (rcu_read_lock){......}, at: [] nf_hook_slow+0x0/0x340 net/netfilter/core.c:267 #2: (rcu_read_lock){......}, at: [] ip6_input_finish+0x0/0x1510 include/linux/skbuff.h:2037 #3: (&(&q->lock)->rlock){+.-...}, at: [] spin_lock include/linux/spinlock.h:302 [inline] #3: (&(&q->lock)->rlock){+.-...}, at: [] ipv6_frag_rcv+0x5eb/0x4f80 net/ipv6/reassembly.c:560 #4: (slock-AF_INET6){+.....}, at: [] spin_trylock include/linux/spinlock.h:312 [inline] #4: (slock-AF_INET6){+.....}, at: [] icmpv6_xmit_lock net/ipv6/icmp.c:120 [inline] #4: (slock-AF_INET6){+.....}, at: [] icmp6_send+0x7db/0x1b70 net/ipv6/icmp.c:485 #5: (rcu_read_lock){......}, at: [] icmp6_send+0xf62/0x1b70 net/ipv6/icmp.c:517 #6: (rcu_read_lock_bh){......}, at: [] ip6_finish_output2+0x1f9/0x1ca0 net/ipv6/ip6_output.c:71 #7: (rcu_read_lock){......}, at: [] ip6_nd_hdr net/ipv6/ndisc.c:427 [inline] #7: (rcu_read_lock){......}, at: [] ndisc_send_skb+0x74d/0x10e0 net/ipv6/ndisc.c:465 #8: (rcu_read_lock_bh){......}, at: [] ip6_finish_output2+0x1f9/0x1ca0 net/ipv6/ip6_output.c:71 #9: (rcu_read_lock_bh){......}, at: [] __dev_queue_xmit+0x1d7/0x1c30 net/core/dev.c:3161 stack backtrace: CPU: 0 PID: 2076 Comm: syz-executor383 Not tainted 4.4.162+ #118 0000000000000000 54da61ae131a217e ffff8801db606138 ffffffff81aa50fd ffffffff83acb9e0 ffffffff83acc250 ffffffff83acb9e0 ffff8800b8200960 ffff8800b8200000 ffff8801db606180 ffffffff813a834a 0000000000000004 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x124 lib/dump_stack.c:51 [] print_circular_bug.cold.34+0x2f7/0x432 kernel/locking/lockdep.c:1226 [] check_prev_add kernel/locking/lockdep.c:1853 [inline] [] check_prevs_add kernel/locking/lockdep.c:1958 [inline] [] validate_chain kernel/locking/lockdep.c:2144 [inline] [] __lock_acquire+0x3e6c/0x5f10 kernel/locking/lockdep.c:3213 [] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592 [] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline] [] _raw_spin_lock+0x36/0x50 kernel/locking/spinlock.c:151 [] spin_lock include/linux/spinlock.h:302 [inline] [] __netif_tx_lock include/linux/netdevice.h:3306 [inline] [] sch_direct_xmit+0x233/0x6c0 net/sched/sch_generic.c:163 [] __dev_xmit_skb net/core/dev.c:2979 [inline] [] __dev_queue_xmit+0xf95/0x1c30 net/core/dev.c:3197 [] dev_queue_xmit+0x17/0x20 net/core/dev.c:3263 [] neigh_resolve_output+0x600/0x780 net/core/neighbour.c:1329 [] dst_neigh_output include/net/dst.h:461 [inline] [] ip6_finish_output2+0xb94/0x1ca0 net/ipv6/ip6_output.c:113 [] ip6_finish_output+0x2ee/0x750 net/ipv6/ip6_output.c:131 [] NF_HOOK_COND include/linux/netfilter.h:240 [inline] [] ip6_output+0x1af/0x520 net/ipv6/ip6_output.c:145 [] dst_output include/net/dst.h:498 [inline] [] NF_HOOK_THRESH include/linux/netfilter.h:226 [inline] [] NF_HOOK include/linux/netfilter.h:249 [inline] [] ndisc_send_skb+0x972/0x10e0 net/ipv6/ndisc.c:471 [] ndisc_send_ns+0x4fb/0x6f0 net/ipv6/ndisc.c:595 [] ndisc_solicit+0x2a0/0x420 net/ipv6/ndisc.c:686 [] neigh_probe+0xca/0x100 net/core/neighbour.c:871 [] __neigh_event_send+0x2a0/0xc30 net/core/neighbour.c:1027 [] neigh_event_send include/net/neighbour.h:431 [inline] [] neigh_resolve_output+0x629/0x780 net/core/neighbour.c:1313 [] dst_neigh_output include/net/dst.h:461 [inline] [] ip6_finish_output2+0xb94/0x1ca0 net/ipv6/ip6_output.c:113 [] ip6_finish_output+0x2ee/0x750 net/ipv6/ip6_output.c:131 [] NF_HOOK_COND include/linux/netfilter.h:240 [inline] [] ip6_output+0x1af/0x520 net/ipv6/ip6_output.c:145 [] dst_output include/net/dst.h:498 [inline] [] ip6_local_out+0x9b/0x180 net/ipv6/output_core.c:169 [] ip6_send_skb+0xa1/0x340 net/ipv6/ip6_output.c:1725 [] ip6_push_pending_frames+0xb3/0xe0 net/ipv6/ip6_output.c:1745 [] icmpv6_push_pending_frames+0x335/0x530 net/ipv6/icmp.c:276 [] icmp6_send+0x15f3/0x1b70 net/ipv6/icmp.c:537 [] icmpv6_param_prob+0x29/0x40 net/ipv6/icmp.c:551 [] ip6_frag_queue net/ipv6/reassembly.c:228 [inline] [] ipv6_frag_rcv+0x3ba5/0x4f80 net/ipv6/reassembly.c:562 [] ip6_input_finish+0x57d/0x1510 net/ipv6/ip6_input.c:248 [] NF_HOOK_THRESH include/linux/netfilter.h:226 [inline] [] NF_HOOK include/linux/netfilter.h:249 [inline] [] ip6_input+0xf6/0x200 net/ipv6/ip6_input.c:280 [] dst_input include/net/dst.h:504 [inline] [] ip6_rcv_finish+0x14e/0x670 net/ipv6/ip6_input.c:62 [] NF_HOOK_THRESH include/linux/netfilter.h:226 [inline] [] ipv6_defrag+0x33b/0x5c0 net/ipv6/netfilter/nf_defrag_ipv6_hooks.c:78 [] nf_iterate+0x182/0x210 net/netfilter/core.c:274 [] nf_hook_slow+0x1b6/0x340 net/netfilter/core.c:306 [] nf_hook_thresh include/linux/netfilter.h:187 [inline] [] NF_HOOK_THRESH include/linux/netfilter.h:224 [inline] [] NF_HOOK include/linux/netfilter.h:249 [inline] [] ipv6_rcv+0x1455/0x1d10 net/ipv6/ip6_input.c:186 [] __netif_receive_skb_core+0x12c8/0x2820 net/core/dev.c:4041 [] __netif_receive_skb+0x5b/0x1c0 net/core/dev.c:4076 [] process_backlog+0x20a/0x670 net/core/dev.c:4669 [] napi_poll net/core/dev.c:4907 [inline] [] net_rx_action+0x367/0xd50 net/core/dev.c:4972 [] __do_softirq+0x22c/0xa1a kernel/softirq.c:273 [] do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:929 [] do_softirq.part.2+0x54/0x60 kernel/softirq.c:317 [] do_softirq+0x19/0x20 kernel/softirq.c:320 [] netif_rx_ni+0xec/0x3a0 net/core/dev.c:3675 [] tun_get_user+0xf3a/0x2690 drivers/net/tun.c:1264 [] tun_chr_write_iter+0xd5/0x190 drivers/net/tun.c:1283 [] do_iter_readv_writev+0x133/0x1d0 fs/read_write.c:664 [] do_readv_writev+0x335/0x6f0 fs/read_write.c:808 [] vfs_writev+0x7b/0xb0 fs/read_write.c:847 [] SYSC_writev fs/read_write.c:880 [inline] [] SyS_writev+0xd9/0x250 fs/read_write.c:872 [] entry_SYSCALL_64_fastpath+0x1e/0x9a