============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- syz.3.2369/13007 is trying to acquire lock: ffff88805b4f6158 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff88805b4f6158 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4710 [inline] ffff88805b4f6158 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: sch_direct_xmit+0x153/0x4b0 net/sched/sch_generic.c:345 but task is already holding lock: ffff888032603d58 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff888032603d58 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4710 [inline] ffff888032603d58 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __dev_direct_xmit+0x39e/0x740 net/core/dev.c:4872 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&qdisc_xmit_lock_key#4); lock(&qdisc_xmit_lock_key#4); *** DEADLOCK *** May be due to missing lock nesting notation 6 locks held by syz.3.2369/13007: #0: ffff888032603d58 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] #0: ffff888032603d58 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4710 [inline] #0: ffff888032603d58 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __dev_direct_xmit+0x39e/0x740 net/core/dev.c:4872 #1: ffffffff8df41aa0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #1: ffffffff8df41aa0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #1: ffffffff8df41aa0 (rcu_read_lock){....}-{1:3}, at: ip_output+0x5b/0x450 net/ipv4/ip_output.c:433 #2: ffffffff8df41aa0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #2: ffffffff8df41aa0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #2: ffffffff8df41aa0 (rcu_read_lock){....}-{1:3}, at: ip_finish_output2+0x3d0/0x1000 net/ipv4/ip_output.c:230 #3: ffffffff8df41aa0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #3: ffffffff8df41aa0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #3: ffffffff8df41aa0 (rcu_read_lock){....}-{1:3}, at: arp_xmit+0x23/0x270 net/ipv4/arp.c:663 #4: ffffffff8df41b00 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #4: ffffffff8df41b00 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:918 [inline] #4: ffffffff8df41b00 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x289/0x31c0 net/core/dev.c:4743 #5: ffff888033201228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: spin_trylock include/linux/spinlock.h:361 [inline] #5: ffff888033201228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: qdisc_run_begin include/net/sch_generic.h:202 [inline] #5: ffff888033201228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: __dev_xmit_skb net/core/dev.c:4155 [inline] #5: ffff888033201228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: __dev_queue_xmit+0xeb9/0x31c0 net/core/dev.c:4784 stack backtrace: CPU: 1 UID: 0 PID: 13007 Comm: syz.3.2369 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_deadlock_bug+0x279/0x290 kernel/locking/lockdep.c:3041 check_deadlock kernel/locking/lockdep.c:3093 [inline] validate_chain kernel/locking/lockdep.c:3895 [inline] __lock_acquire+0x2540/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] __netif_tx_lock include/linux/netdevice.h:4710 [inline] sch_direct_xmit+0x153/0x4b0 net/sched/sch_generic.c:345 __dev_xmit_skb net/core/dev.c:4168 [inline] __dev_queue_xmit+0x1379/0x31c0 net/core/dev.c:4784 NF_HOOK+0x310/0x3a0 include/linux/netfilter.h:-1 arp_xmit+0x16c/0x270 net/ipv4/arp.c:665 arp_solicit+0xbbd/0xe10 net/ipv4/arp.c:392 neigh_probe net/core/neighbour.c:1097 [inline] __neigh_event_send+0xf3e/0x1520 net/core/neighbour.c:1270 neigh_event_send_probe include/net/neighbour.h:480 [inline] neigh_event_send include/net/neighbour.h:486 [inline] neigh_resolve_output+0x198/0x750 net/core/neighbour.c:1578 neigh_output include/net/neighbour.h:556 [inline] ip_finish_output2+0xbb6/0x1000 net/ipv4/ip_output.c:237 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip_output+0x29f/0x450 net/ipv4/ip_output.c:438 iptunnel_xmit+0x5f8/0xa90 net/ipv4/ip_tunnel_core.c:84 ip_tunnel_xmit+0x1c41/0x2390 net/ipv4/ip_tunnel.c:845 __gre_xmit net/ipv4/ip_gre.c:490 [inline] ipgre_xmit+0x89e/0xc50 net/ipv4/ip_gre.c:694 __netdev_start_xmit include/linux/netdevice.h:5273 [inline] netdev_start_xmit include/linux/netdevice.h:5282 [inline] __dev_direct_xmit+0x4a3/0x740 net/core/dev.c:4874 dev_direct_xmit include/linux/netdevice.h:3394 [inline] packet_xmit+0x1b4/0x330 net/packet/af_packet.c:284 packet_snd net/packet/af_packet.c:3076 [inline] packet_sendmsg+0x3e33/0x5080 net/packet/af_packet.c:3108 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg+0x21c/0x270 net/socket.c:742 __sys_sendto+0x3bd/0x520 net/socket.c:2206 __do_sys_sendto net/socket.c:2213 [inline] __se_sys_sendto net/socket.c:2209 [inline] __x64_sys_sendto+0xde/0x100 net/socket.c:2209 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f412ff8f749 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f4130dd0038 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007f41301e5fa0 RCX: 00007f412ff8f749 RDX: 0000000000000021 RSI: 0000200000000240 RDI: 0000000000000003 RBP: 00007f4130013f91 R08: 0000200000000540 R09: 0000000000000014 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f41301e6038 R14: 00007f41301e5fa0 R15: 00007ffe9bb185c8