============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- syz.3.785/6975 is trying to acquire lock: ffff888075fcd398 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline] ffff888075fcd398 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4446 [inline] ffff888075fcd398 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x162/0x4b0 net/sched/sch_generic.c:343 but task is already holding lock: ffff88801fc03898 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline] ffff88801fc03898 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4446 [inline] ffff88801fc03898 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x162/0x4b0 net/sched/sch_generic.c:343 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 11 locks held by syz.3.785/6975: #0: ffffffff8c31f320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #1: ffffffff8c31f380 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #2: ffffffff8c31f320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #3: ffffffff8c31f380 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #4: ffffffff8c31f380 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #5: ffff888077d4e258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_trylock include/linux/spinlock.h:374 [inline] #5: ffff888077d4e258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:173 [inline] #5: ffff888077d4e258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3884 [inline] #5: ffff888077d4e258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x1120/0x2f80 net/core/dev.c:4266 #6: ffff88801fc03898 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline] #6: ffff88801fc03898 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4446 [inline] #6: ffff88801fc03898 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x162/0x4b0 net/sched/sch_generic.c:343 #7: ffffffff8c31f320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #8: ffffffff8c31f380 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #9: ffffffff8c31f380 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #10: ffff888075575258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_trylock include/linux/spinlock.h:374 [inline] #10: ffff888075575258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:173 [inline] #10: ffff888075575258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3884 [inline] #10: ffff888075575258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x1120/0x2f80 net/core/dev.c:4266 stack backtrace: CPU: 0 PID: 6975 Comm: syz.3.785 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 Call Trace: dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106 __lock_acquire+0x1236/0x7d10 kernel/locking/lockdep.c:-1 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 __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:364 [inline] __netif_tx_lock include/linux/netdevice.h:4446 [inline] sch_direct_xmit+0x162/0x4b0 net/sched/sch_generic.c:343 __dev_xmit_skb net/core/dev.c:3897 [inline] __dev_queue_xmit+0x179f/0x2f80 net/core/dev.c:4266 neigh_output include/net/neighbour.h:509 [inline] ip_finish_output2+0xcbf/0x10a0 net/ipv4/ip_output.c:228 NF_HOOK_COND include/linux/netfilter.h:291 [inline] ip_output+0x2c0/0x3e0 net/ipv4/ip_output.c:434 iptunnel_xmit+0x4d6/0x8e0 net/ipv4/ip_tunnel_core.c:82 ip_tunnel_xmit+0x1905/0x2280 net/ipv4/ip_tunnel.c:824 __gre_xmit net/ipv4/ip_gre.c:474 [inline] erspan_xmit+0x9d5/0x15a0 net/ipv4/ip_gre.c:723 __netdev_start_xmit include/linux/netdevice.h:5036 [inline] netdev_start_xmit include/linux/netdevice.h:5050 [inline] xmit_one net/core/dev.c:3662 [inline] dev_hard_start_xmit+0x2a5/0x7e0 net/core/dev.c:3678 sch_direct_xmit+0x25a/0x4b0 net/sched/sch_generic.c:345 __dev_xmit_skb net/core/dev.c:3897 [inline] __dev_queue_xmit+0x179f/0x2f80 net/core/dev.c:4266 neigh_output include/net/neighbour.h:509 [inline] ip_finish_output2+0xcbf/0x10a0 net/ipv4/ip_output.c:228 NF_HOOK_COND include/linux/netfilter.h:291 [inline] ip_output+0x2c0/0x3e0 net/ipv4/ip_output.c:434 iptunnel_xmit+0x4d6/0x8e0 net/ipv4/ip_tunnel_core.c:82 ip_tunnel_xmit+0x1905/0x2280 net/ipv4/ip_tunnel.c:824 __gre_xmit net/ipv4/ip_gre.c:474 [inline] ipgre_xmit+0x779/0xb00 net/ipv4/ip_gre.c:669 __netdev_start_xmit include/linux/netdevice.h:5036 [inline] netdev_start_xmit include/linux/netdevice.h:5050 [inline] xmit_one net/core/dev.c:3662 [inline] dev_hard_start_xmit+0x2a5/0x7e0 net/core/dev.c:3678 __dev_queue_xmit+0x1a9b/0x2f80 net/core/dev.c:4305 __bpf_tx_skb net/core/filter.c:2127 [inline] __bpf_redirect_no_mac net/core/filter.c:2161 [inline] __bpf_redirect+0x6ad/0xee0 net/core/filter.c:2184 ____bpf_clone_redirect net/core/filter.c:2462 [inline] bpf_clone_redirect+0x2e2/0x470 net/core/filter.c:2425 bpf_prog_208b094576c80b22+0x56/0x790 bpf_dispatcher_nop_func include/linux/bpf.h:888 [inline] __bpf_prog_run include/linux/filter.h:628 [inline] bpf_prog_run include/linux/filter.h:635 [inline] bpf_test_run+0x2a8/0x800 net/bpf/test_run.c:119 bpf_prog_test_run_skb+0x9cc/0x1180 net/bpf/test_run.c:674 bpf_prog_test_run+0x31e/0x390 kernel/bpf/syscall.c:3374 __sys_bpf+0x5a5/0x6f0 kernel/bpf/syscall.c:4675 __do_sys_bpf kernel/bpf/syscall.c:4761 [inline] __se_sys_bpf kernel/bpf/syscall.c:4759 [inline] __x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4759 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 RIP: 0033:0x7f0a66abce59 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f0a64d16028 EFLAGS: 00000246 ORIG_RAX: 0000000000000141 RAX: ffffffffffffffda RBX: 00007f0a66d35fa0 RCX: 00007f0a66abce59 RDX: 0000000000000050 RSI: 00002000000000c0 RDI: 000000000000000a RBP: 00007f0a66b52d6f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f0a66d36038 R14: 00007f0a66d35fa0 R15: 00007ffd903ca928