============================================ WARNING: possible recursive locking detected 5.14.0-syzkaller #0 Not tainted -------------------------------------------- syz-executor.1/20333 is trying to acquire lock: ffff88807d675398 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] ffff88807d675398 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4405 [inline] ffff88807d675398 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x30f/0xbb0 net/sched/sch_generic.c:340 but task is already holding lock: ffff8880123d3098 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] ffff8880123d3098 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4405 [inline] ffff8880123d3098 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x30f/0xbb0 net/sched/sch_generic.c:340 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 9 locks held by syz-executor.1/20333: #0: ffff888147b4bea0 (l2tp_sock){+...}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #0: ffff888147b4bea0 (l2tp_sock){+...}-{2:2}, at: l2tp_xmit_core net/l2tp/l2tp_core.c:1044 [inline] #0: ffff888147b4bea0 (l2tp_sock){+...}-{2:2}, at: l2tp_xmit_skb+0x57a/0x18f0 net/l2tp/l2tp_core.c:1109 #1: ffffffff8b97f960 (rcu_read_lock){....}-{1:2}, at: read_pnet include/net/net_namespace.h:327 [inline] #1: ffffffff8b97f960 (rcu_read_lock){....}-{1:2}, at: sock_net include/net/sock.h:2602 [inline] #1: ffffffff8b97f960 (rcu_read_lock){....}-{1:2}, at: __ip_queue_xmit+0x3d/0x1bb0 net/ipv4/ip_output.c:450 #2: ffffffff8b97f900 (rcu_read_lock_bh){....}-{1:2}, at: lwtunnel_xmit_redirect include/net/lwtunnel.h:95 [inline] #2: ffffffff8b97f900 (rcu_read_lock_bh){....}-{1:2}, at: ip_finish_output2+0x28b/0x2140 net/ipv4/ip_output.c:207 #3: ffffffff8b97f900 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x1da/0x3710 net/core/dev.c:4136 #4: ffff88803062b258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: spin_trylock include/linux/spinlock.h:373 [inline] #4: ffff88803062b258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:173 [inline] #4: ffff88803062b258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3790 [inline] #4: ffff88803062b258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_queue_xmit+0x125c/0x3710 net/core/dev.c:4170 #5: ffff8880123d3098 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #5: ffff8880123d3098 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4405 [inline] #5: ffff8880123d3098 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x30f/0xbb0 net/sched/sch_generic.c:340 #6: ffffffff8b97f900 (rcu_read_lock_bh){....}-{1:2}, at: lwtunnel_xmit_redirect include/net/lwtunnel.h:95 [inline] #6: ffffffff8b97f900 (rcu_read_lock_bh){....}-{1:2}, at: ip_finish_output2+0x28b/0x2140 net/ipv4/ip_output.c:207 #7: ffffffff8b97f900 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x1da/0x3710 net/core/dev.c:4136 #8: ffff8880400a3258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: spin_trylock include/linux/spinlock.h:373 [inline] #8: ffff8880400a3258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:173 [inline] #8: ffff8880400a3258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3790 [inline] #8: ffff8880400a3258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_queue_xmit+0x125c/0x3710 net/core/dev.c:4170 stack backtrace: CPU: 1 PID: 20333 Comm: syz-executor.1 Not tainted 5.14.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105 print_deadlock_bug kernel/locking/lockdep.c:2944 [inline] check_deadlock kernel/locking/lockdep.c:2987 [inline] validate_chain kernel/locking/lockdep.c:3776 [inline] __lock_acquire.cold+0x149/0x3ab kernel/locking/lockdep.c:5015 lock_acquire kernel/locking/lockdep.c:5625 [inline] lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:363 [inline] __netif_tx_lock include/linux/netdevice.h:4405 [inline] sch_direct_xmit+0x30f/0xbb0 net/sched/sch_generic.c:340 __dev_xmit_skb net/core/dev.c:3803 [inline] __dev_queue_xmit+0x14c3/0x3710 net/core/dev.c:4170 neigh_resolve_output net/core/neighbour.c:1492 [inline] neigh_resolve_output+0x50e/0x820 net/core/neighbour.c:1472 neigh_output include/net/neighbour.h:510 [inline] ip_finish_output2+0x813/0x2140 net/ipv4/ip_output.c:221 __ip_finish_output net/ipv4/ip_output.c:299 [inline] __ip_finish_output+0x396/0x640 net/ipv4/ip_output.c:281 ip_finish_output+0x32/0x200 net/ipv4/ip_output.c:309 NF_HOOK_COND include/linux/netfilter.h:296 [inline] ip_mc_output+0x212/0x700 net/ipv4/ip_output.c:408 dst_output include/net/dst.h:450 [inline] ip_local_out+0xaf/0x1a0 net/ipv4/ip_output.c:126 iptunnel_xmit+0x628/0xa50 net/ipv4/ip_tunnel_core.c:82 ip_tunnel_xmit+0x10a6/0x2b60 net/ipv4/ip_tunnel.c:810 erspan_xmit+0x7e2/0x29c0 net/ipv4/ip_gre.c:709 __netdev_start_xmit include/linux/netdevice.h:4970 [inline] netdev_start_xmit include/linux/netdevice.h:4984 [inline] xmit_one net/core/dev.c:3576 [inline] dev_hard_start_xmit+0x1eb/0x920 net/core/dev.c:3592 sch_direct_xmit+0x19f/0xbb0 net/sched/sch_generic.c:342 __dev_xmit_skb net/core/dev.c:3803 [inline] __dev_queue_xmit+0x14c3/0x3710 net/core/dev.c:4170 neigh_resolve_output net/core/neighbour.c:1492 [inline] neigh_resolve_output+0x50e/0x820 net/core/neighbour.c:1472 neigh_output include/net/neighbour.h:510 [inline] ip_finish_output2+0x813/0x2140 net/ipv4/ip_output.c:221 __ip_finish_output net/ipv4/ip_output.c:299 [inline] __ip_finish_output+0x396/0x640 net/ipv4/ip_output.c:281 ip_finish_output+0x32/0x200 net/ipv4/ip_output.c:309 NF_HOOK_COND include/linux/netfilter.h:296 [inline] ip_mc_output+0x212/0x700 net/ipv4/ip_output.c:408 dst_output include/net/dst.h:450 [inline] ip_local_out net/ipv4/ip_output.c:126 [inline] __ip_queue_xmit+0x97e/0x1bb0 net/ipv4/ip_output.c:525 l2tp_xmit_queue net/l2tp/l2tp_core.c:1007 [inline] l2tp_xmit_core net/l2tp/l2tp_core.c:1093 [inline] l2tp_xmit_skb+0xaff/0x18f0 net/l2tp/l2tp_core.c:1109 pppol2tp_sendmsg+0x4d2/0x7c0 net/l2tp/l2tp_ppp.c:319 sock_sendmsg_nosec net/socket.c:704 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:724 ____sys_sendmsg+0x331/0x810 net/socket.c:2409 ___sys_sendmsg+0xf3/0x170 net/socket.c:2463 __sys_sendmmsg+0x195/0x470 net/socket.c:2549 __do_sys_sendmmsg net/socket.c:2578 [inline] __se_sys_sendmmsg net/socket.c:2575 [inline] __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2575 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x4665f9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fbabebe7188 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665f9 RDX: 0400000000000085 RSI: 0000000020000280 RDI: 0000000000000003 RBP: 00000000004bfcc4 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80 R13: 00007ffd0784b7cf R14: 00007fbabebe7300 R15: 0000000000022000