============================================ WARNING: possible recursive locking detected 6.1.147-syzkaller #0 Not tainted -------------------------------------------- syz.9.3348/18034 is trying to acquire lock: ffff888026374218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff888026374218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3925 [inline] ffff888026374218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x208f/0x3760 net/core/dev.c:4300 but task is already holding lock: ffff888056a3f258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_trylock include/linux/spinlock.h:361 [inline] ffff888056a3f258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:195 [inline] ffff888056a3f258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3882 [inline] ffff888056a3f258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x129a/0x3760 net/core/dev.c:4300 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock); lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock); *** DEADLOCK *** May be due to missing lock nesting notation 10 locks held by syz.9.3348/18034: #0: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline] #0: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline] #0: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: ip6_send_skb+0x10b/0x380 net/ipv6/ip6_output.c:2008 #1: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline] #1: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline] #1: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: ip6_finish_output2+0x593/0x1590 net/ipv6/ip6_output.c:123 #2: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #2: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_read_lock_bh include/linux/rcupdate.h:843 [inline] #2: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x26f/0x3760 net/core/dev.c:4257 #3: ffff888056a3f258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_trylock include/linux/spinlock.h:361 [inline] #3: ffff888056a3f258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:195 [inline] #3: ffff888056a3f258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3882 [inline] #3: ffff888056a3f258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x129a/0x3760 net/core/dev.c:4300 #4: ffff88804d52f8d8 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] #4: ffff88804d52f8d8 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4347 [inline] #4: ffff88804d52f8d8 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x156/0x4a0 net/sched/sch_generic.c:340 #5: ffff88802ffe00b0 (k-slock-AF_INET6){+.-.}-{2:2}, at: spin_trylock include/linux/spinlock.h:361 [inline] #5: ffff88802ffe00b0 (k-slock-AF_INET6){+.-.}-{2:2}, at: icmpv6_xmit_lock net/ipv6/icmp.c:108 [inline] #5: ffff88802ffe00b0 (k-slock-AF_INET6){+.-.}-{2:2}, at: icmp6_send+0xb5f/0x18d0 net/ipv6/icmp.c:553 #6: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #6: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: icmp6_send+0xaa6/0x18d0 net/ipv6/icmp.c:544 #7: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline] #7: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline] #7: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: ip6_send_skb+0x10b/0x380 net/ipv6/ip6_output.c:2008 #8: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline] #8: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline] #8: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: ip6_finish_output2+0x593/0x1590 net/ipv6/ip6_output.c:123 #9: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #9: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_read_lock_bh include/linux/rcupdate.h:843 [inline] #9: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x26f/0x3760 net/core/dev.c:4257 stack backtrace: CPU: 0 PID: 18034 Comm: syz.9.3348 Not tainted 6.1.147-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 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] __dev_xmit_skb net/core/dev.c:3925 [inline] __dev_queue_xmit+0x208f/0x3760 net/core/dev.c:4300 dev_queue_xmit include/linux/netdevice.h:3051 [inline] neigh_hh_output include/net/neighbour.h:528 [inline] neigh_output include/net/neighbour.h:542 [inline] ip6_finish_output2+0xd6b/0x1590 net/ipv6/ip6_output.c:138 ip6_send_skb+0x1d1/0x380 net/ipv6/ip6_output.c:2009 icmp6_send+0x1292/0x18d0 net/ipv6/icmp.c:632 __icmpv6_send include/linux/icmpv6.h:28 [inline] icmpv6_send include/linux/icmpv6.h:49 [inline] ip6_link_failure+0x37/0x4c0 net/ipv6/route.c:2827 ip_tunnel_xmit+0x1748/0x2360 net/ipv4/ip_tunnel.c:864 __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 dev_queue_xmit include/linux/netdevice.h:3051 [inline] neigh_hh_output include/net/neighbour.h:528 [inline] neigh_output include/net/neighbour.h:542 [inline] ip6_finish_output2+0xd6b/0x1590 net/ipv6/ip6_output.c:138 ip6_send_skb+0x1d1/0x380 net/ipv6/ip6_output.c:2009 udp_v6_send_skb+0xb62/0x17f0 net/ipv6/udp.c:1305 udpv6_sendmsg+0x1c3e/0x2370 net/ipv6/udp.c:1600 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_sendmmsg+0x272/0x490 net/socket.c:2659 __do_sys_sendmmsg net/socket.c:2688 [inline] __se_sys_sendmmsg net/socket.c:2685 [inline] __x64_sys_sendmmsg+0x9c/0xb0 net/socket.c:2685 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: 0033:0x7f9deeb8eb69 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:00007f9def96d038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 00007f9deedb6160 RCX: 00007f9deeb8eb69 RDX: 0000000000006c00 RSI: 0000200000007e40 RDI: 0000000000000003 RBP: 00007f9deec11df1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000048 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f9deedb6160 R15: 00007fffae944928