============================================ WARNING: possible recursive locking detected 6.1.140-syzkaller #0 Not tainted -------------------------------------------- syz.2.17/4382 is trying to acquire lock: ffff888024ce1458 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff888024ce1458 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4347 [inline] ffff888024ce1458 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x156/0x4a0 net/sched/sch_generic.c:340 but task is already holding lock: ffff8880287498d8 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff8880287498d8 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4347 [inline] ffff8880287498d8 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x156/0x4a0 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 7 locks held by syz.2.17/4382: #0: ffffffff8c92ab20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline] #0: ffffffff8c92ab20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline] #0: ffffffff8c92ab20 (rcu_read_lock){....}-{1:2}, at: ip_finish_output2+0x3e8/0x11b0 net/ipv4/ip_output.c:221 #1: ffffffff8c92ab80 (rcu_read_lock_bh){....}-{1:2}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #1: ffffffff8c92ab80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_read_lock_bh include/linux/rcupdate.h:843 [inline] #1: ffffffff8c92ab80 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x26f/0x3760 net/core/dev.c:4257 #2: ffff88802857a258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_trylock include/linux/spinlock.h:361 [inline] #2: ffff88802857a258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:195 [inline] #2: ffff88802857a258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3882 [inline] #2: ffff88802857a258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x129a/0x3760 net/core/dev.c:4300 #3: ffff8880287498d8 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] #3: ffff8880287498d8 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4347 [inline] #3: ffff8880287498d8 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x156/0x4a0 net/sched/sch_generic.c:340 #4: ffffffff8c92ab20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline] #4: ffffffff8c92ab20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline] #4: ffffffff8c92ab20 (rcu_read_lock){....}-{1:2}, at: ip_finish_output2+0x3e8/0x11b0 net/ipv4/ip_output.c:221 #5: ffffffff8c92ab80 (rcu_read_lock_bh){....}-{1:2}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #5: ffffffff8c92ab80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_read_lock_bh include/linux/rcupdate.h:843 [inline] #5: ffffffff8c92ab80 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x26f/0x3760 net/core/dev.c:4257 #6: ffff88807937f258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_trylock include/linux/spinlock.h:361 [inline] #6: ffff88807937f258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:195 [inline] #6: ffff88807937f258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3882 [inline] #6: ffff88807937f258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x129a/0x3760 net/core/dev.c:4300 stack backtrace: CPU: 1 PID: 4382 Comm: syz.2.17 Not tainted 6.1.140-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call Trace: dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106 __lock_acquire+0x122f/0x7c50 kernel/locking/lockdep.c:-1 lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] __netif_tx_lock include/linux/netdevice.h:4347 [inline] sch_direct_xmit+0x156/0x4a0 net/sched/sch_generic.c:340 __dev_xmit_skb net/core/dev.c:3895 [inline] __dev_queue_xmit+0x18cd/0x3760 net/core/dev.c:4300 neigh_output include/net/neighbour.h:544 [inline] ip_finish_output2+0xd05/0x11b0 net/ipv4/ip_output.c:228 iptunnel_xmit+0x525/0x930 net/ipv4/ip_tunnel_core.c:82 ip_tunnel_xmit+0x1c39/0x2360 net/ipv4/ip_tunnel.c:858 __gre_xmit net/ipv4/ip_gre.c:474 [inline] erspan_xmit+0x9a5/0x1560 net/ipv4/ip_gre.c:723 __netdev_start_xmit include/linux/netdevice.h:4896 [inline] netdev_start_xmit include/linux/netdevice.h:4910 [inline] xmit_one net/core/dev.c:3658 [inline] dev_hard_start_xmit+0x262/0x870 net/core/dev.c:3674 sch_direct_xmit+0x24e/0x4a0 net/sched/sch_generic.c:342 __dev_xmit_skb net/core/dev.c:3895 [inline] __dev_queue_xmit+0x18cd/0x3760 net/core/dev.c:4300 neigh_output include/net/neighbour.h:544 [inline] ip_finish_output2+0xd05/0x11b0 net/ipv4/ip_output.c:228 dst_output include/net/dst.h:453 [inline] ip_local_out net/ipv4/ip_output.c:126 [inline] ip_send_skb+0x129/0x1c0 net/ipv4/ip_output.c:1600 udp_send_skb+0xa88/0x1580 net/ipv4/udp.c:993 udp_sendmsg+0x1a31/0x23d0 net/ipv4/udp.c:1281 sock_sendmsg_nosec net/socket.c:718 [inline] __sock_sendmsg net/socket.c:730 [inline] ____sys_sendmsg+0x59b/0x970 net/socket.c:2519 ___sys_sendmsg+0x21c/0x290 net/socket.c:2573 __sys_sendmsg net/socket.c:2602 [inline] __do_sys_sendmsg net/socket.c:2611 [inline] __se_sys_sendmsg+0x19e/0x270 net/socket.c:2609 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7f028678e969 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:00007f028766b038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f02869b5fa0 RCX: 00007f028678e969 RDX: 0000000000000000 RSI: 0000200000000380 RDI: 0000000000000003 RBP: 00007f0286810ab1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f02869b5fa0 R15: 00007ffc11776258