============================================ WARNING: possible recursive locking detected 4.15.0-rc7-next-20180112+ #96 Not tainted -------------------------------------------- syzkaller031107/3666 is trying to acquire lock: (_xmit_ETHER#2){+.-.}, at: [<000000007361185e>] spin_lock include/linux/spinlock.h:310 [inline] (_xmit_ETHER#2){+.-.}, at: [<000000007361185e>] __netif_tx_lock include/linux/netdevice.h:3541 [inline] (_xmit_ETHER#2){+.-.}, at: [<000000007361185e>] sch_direct_xmit+0x361/0x1140 net/sched/sch_generic.c:325 but task is already holding lock: (_xmit_ETHER#2){+.-.}, at: [<000000007361185e>] spin_lock include/linux/spinlock.h:310 [inline] (_xmit_ETHER#2){+.-.}, at: [<000000007361185e>] __netif_tx_lock include/linux/netdevice.h:3541 [inline] (_xmit_ETHER#2){+.-.}, at: [<000000007361185e>] sch_direct_xmit+0x361/0x1140 net/sched/sch_generic.c:325 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(_xmit_ETHER#2); lock(_xmit_ETHER#2); *** DEADLOCK *** May be due to missing lock nesting notation 8 locks held by syzkaller031107/3666: #0: (&tfile->napi_mutex){+.+.}, at: [<00000000267a68e4>] tun_get_user+0xe6c/0x3940 drivers/net/tun.c:1783 #1: (rcu_read_lock){....}, at: [<000000009857927e>] arch_static_branch arch/x86/include/asm/jump_label.h:36 [inline] #1: (rcu_read_lock){....}, at: [<000000009857927e>] static_key_false include/linux/jump_label.h:142 [inline] #1: (rcu_read_lock){....}, at: [<000000009857927e>] netif_receive_skb_internal+0xa2/0x670 net/core/dev.c:4651 #2: (k-slock-AF_INET){+...}, at: [<000000007070ab21>] spin_trylock include/linux/spinlock.h:320 [inline] #2: (k-slock-AF_INET){+...}, at: [<000000007070ab21>] icmp_xmit_lock net/ipv4/icmp.c:219 [inline] #2: (k-slock-AF_INET){+...}, at: [<000000007070ab21>] icmp_send+0x758/0x19b0 net/ipv4/icmp.c:668 #3: (rcu_read_lock_bh){....}, at: [<0000000061ec4805>] lwtunnel_xmit_redirect include/net/lwtunnel.h:92 [inline] #3: (rcu_read_lock_bh){....}, at: [<0000000061ec4805>] ip_finish_output2+0x2aa/0x14f0 net/ipv4/ip_output.c:213 #4: (rcu_read_lock_bh){....}, at: [<0000000002c23d24>] __dev_queue_xmit+0x2d8/0x2b50 net/core/dev.c:3467 #5: (_xmit_ETHER#2){+.-.}, at: [<000000007361185e>] spin_lock include/linux/spinlock.h:310 [inline] #5: (_xmit_ETHER#2){+.-.}, at: [<000000007361185e>] __netif_tx_lock include/linux/netdevice.h:3541 [inline] #5: (_xmit_ETHER#2){+.-.}, at: [<000000007361185e>] sch_direct_xmit+0x361/0x1140 net/sched/sch_generic.c:325 #6: (rcu_read_lock_bh){....}, at: [<0000000061ec4805>] lwtunnel_xmit_redirect include/net/lwtunnel.h:92 [inline] #6: (rcu_read_lock_bh){....}, at: [<0000000061ec4805>] ip_finish_output2+0x2aa/0x14f0 net/ipv4/ip_output.c:213 #7: (rcu_read_lock_bh){....}, at: [<0000000002c23d24>] __dev_queue_xmit+0x2d8/0x2b50 net/core/dev.c:3467 stack backtrace: CPU: 1 PID: 3666 Comm: syzkaller031107 Not tainted 4.15.0-rc7-next-20180112+ #96 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 print_deadlock_bug kernel/locking/lockdep.c:1756 [inline] check_deadlock kernel/locking/lockdep.c:1800 [inline] validate_chain kernel/locking/lockdep.c:2396 [inline] __lock_acquire+0xe8f/0x3e00 kernel/locking/lockdep.c:3426 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3914 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:144 spin_lock include/linux/spinlock.h:310 [inline] __netif_tx_lock include/linux/netdevice.h:3541 [inline] sch_direct_xmit+0x361/0x1140 net/sched/sch_generic.c:325 qdisc_restart net/sched/sch_generic.c:393 [inline] __qdisc_run+0x57d/0x19c0 net/sched/sch_generic.c:401 __dev_xmit_skb net/core/dev.c:3200 [inline] __dev_queue_xmit+0xb62/0x2b50 net/core/dev.c:3501 dev_queue_xmit+0x17/0x20 net/core/dev.c:3566 neigh_resolve_output+0x5e2/0xa00 net/core/neighbour.c:1350 neigh_output include/net/neighbour.h:482 [inline] ip_finish_output2+0x8c6/0x14f0 net/ipv4/ip_output.c:229 ip_finish_output+0x864/0xd10 net/ipv4/ip_output.c:317 NF_HOOK_COND include/linux/netfilter.h:277 [inline] ip_mc_output+0x271/0x1350 net/ipv4/ip_output.c:390 dst_output include/net/dst.h:443 [inline] ip_local_out+0x95/0x160 net/ipv4/ip_output.c:124 iptunnel_xmit+0x556/0x810 net/ipv4/ip_tunnel_core.c:91 ip_tunnel_xmit+0x1780/0x3650 net/ipv4/ip_tunnel.c:786 __gre_xmit+0x546/0x8b0 net/ipv4/ip_gre.c:461 erspan_xmit+0x7eb/0x2430 net/ipv4/ip_gre.c:744 __netdev_start_xmit include/linux/netdevice.h:4046 [inline] netdev_start_xmit include/linux/netdevice.h:4055 [inline] xmit_one net/core/dev.c:3020 [inline] dev_hard_start_xmit+0x24e/0xac0 net/core/dev.c:3036 sch_direct_xmit+0x40d/0x1140 net/sched/sch_generic.c:327 qdisc_restart net/sched/sch_generic.c:393 [inline] __qdisc_run+0x57d/0x19c0 net/sched/sch_generic.c:401 __dev_xmit_skb net/core/dev.c:3200 [inline] __dev_queue_xmit+0xb62/0x2b50 net/core/dev.c:3501 dev_queue_xmit+0x17/0x20 net/core/dev.c:3566 neigh_resolve_output+0x5e2/0xa00 net/core/neighbour.c:1350 neigh_output include/net/neighbour.h:482 [inline] ip_finish_output2+0x8c6/0x14f0 net/ipv4/ip_output.c:229 ip_finish_output+0x864/0xd10 net/ipv4/ip_output.c:317 NF_HOOK_COND include/linux/netfilter.h:277 [inline] ip_mc_output+0x271/0x1350 net/ipv4/ip_output.c:390 dst_output include/net/dst.h:443 [inline] ip_local_out+0x95/0x160 net/ipv4/ip_output.c:124 ip_send_skb+0x3c/0xc0 net/ipv4/ip_output.c:1414 ip_push_pending_frames+0x64/0x80 net/ipv4/ip_output.c:1434 icmp_push_reply+0x395/0x4f0 net/ipv4/icmp.c:394 icmp_send+0x1136/0x19b0 net/ipv4/icmp.c:741 ip_options_compile+0xc21/0x1a50 net/ipv4/ip_options.c:472 ip_rcv_options net/ipv4/ip_input.c:284 [inline] ip_rcv_finish+0x80f/0x1e30 net/ipv4/ip_input.c:365 NF_HOOK include/linux/netfilter.h:288 [inline] ip_rcv+0xc5a/0x1840 net/ipv4/ip_input.c:493 __netif_receive_skb_core+0x1a41/0x3460 net/core/dev.c:4538 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4603 netif_receive_skb_internal+0x10b/0x670 net/core/dev.c:4677 napi_frags_finish net/core/dev.c:5118 [inline] napi_gro_frags+0x58a/0xaf0 net/core/dev.c:5191 tun_get_user+0x2760/0x3940 drivers/net/tun.c:1907 tun_chr_write_iter+0xb9/0x160 drivers/net/tun.c:1952 call_write_iter include/linux/fs.h:1775 [inline] do_iter_readv_writev+0x525/0x7f0 fs/read_write.c:653 do_iter_write+0x154/0x540 fs/read_write.c:932 vfs_writev+0x18a/0x340 fs/read_write.c:977 do_writev+0xfc/0x2a0 fs/read_write.c:1012 SYSC_writev fs/read_write.c:1085 [inline] SyS_writev+0x27/0x30 fs/read_write.c:1082 entry_SYSCALL_64_fastpath+0x29/0xa0 RIP: 0033:0x444f50 RSP: 002b:00007ffdafdd3338 EFLAGS: 00000246 ORIG_RAX: 0000000000000014 RAX: ffffffffffffffda RBX: 00000000004a6852 RCX: 0000000000444f50 RDX: 0000000000000001 RSI: 00007ffdafdd3370 RDI: 0000000000000003 RBP: 00007ffdafdd3468 R08: 0000000000000023 R09: 0000000000000000 R10: 0000000000000000 R11: 000000000