======================================================
WARNING: possible circular locking dependency detected
5.15.164-syzkaller #0 Not tainted
------------------------------------------------------
syz.3.779/6557 is trying to acquire lock:
ffff888075660218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
ffff888075660218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3869 [inline]
ffff888075660218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x2184/0x3230 net/core/dev.c:4213

but task is already holding lock:
ffff888065a97498 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
ffff888065a97498 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4429 [inline]
ffff888065a97498 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x1c0/0x5e0 net/sched/sch_generic.c:340

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (_xmit_ETHER#2
){+.-.}-{2:2}
:
       lock_acquire+0x1db/0x4f0 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:363 [inline]
       __netif_tx_lock include/linux/netdevice.h:4429 [inline]
       sch_direct_xmit+0x1c0/0x5e0 net/sched/sch_generic.c:340
       __dev_xmit_skb net/core/dev.c:3844 [inline]
       __dev_queue_xmit+0x18ee/0x3230 net/core/dev.c:4213
       lapb_data_transmit+0x85/0xa0 net/lapb/lapb_iface.c:447
       lapb_transmit_buffer+0x164/0x1e0 net/lapb/lapb_out.c:149
       lapb_establish_data_link+0x80/0xd0
       lapb_device_event+0x4a6/0x630
       notifier_call_chain kernel/notifier.c:83 [inline]
       raw_notifier_call_chain+0xd0/0x170 kernel/notifier.c:391
       __dev_notify_flags+0x304/0x610
       dev_change_flags+0xe7/0x190 net/core/dev.c:8889
       devinet_ioctl+0x92e/0x1b20 net/ipv4/devinet.c:1142
       inet_ioctl+0x32d/0x400 net/ipv4/af_inet.c:989
       sock_do_ioctl+0x11d/0x5a0 net/socket.c:1140
       sock_ioctl+0x47f/0x770 net/socket.c:1257
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:860
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
       __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
       lock_acquire+0x1db/0x4f0 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:363 [inline]
       __dev_xmit_skb net/core/dev.c:3869 [inline]
       __dev_queue_xmit+0x2184/0x3230 net/core/dev.c:4213
       neigh_output include/net/neighbour.h:509 [inline]
       ip6_finish_output2+0xee8/0x14f0 net/ipv6/ip6_output.c:126
       dst_output include/net/dst.h:443 [inline]
       NF_HOOK include/linux/netfilter.h:302 [inline]
       ndisc_send_skb+0xae0/0x13c0 net/ipv6/ndisc.c:509
       ndisc_send_ns+0x64d/0x830 net/ipv6/ndisc.c:651
       ndisc_solicit+0x3cd/0x570
       neigh_probe net/core/neighbour.c:1017 [inline]
       __neigh_event_send+0xe8e/0x1470 net/core/neighbour.c:1178
       neigh_event_send include/net/neighbour.h:438 [inline]
       neigh_resolve_output+0x1d3/0x6d0 net/core/neighbour.c:1488
       neigh_output include/net/neighbour.h:509 [inline]
       ip6_finish_output2+0xee8/0x14f0 net/ipv6/ip6_output.c:126
       ip6_send_skb+0x12b/0x240 net/ipv6/ip6_output.c:1943
       icmp6_send+0x1732/0x21e0 net/ipv6/icmp.c:630
       __icmpv6_send include/linux/icmpv6.h:28 [inline]
       icmpv6_send include/linux/icmpv6.h:49 [inline]
       ip6_link_failure+0x37/0x4a0 net/ipv6/route.c:2794
       ip_tunnel_xmit+0x1cee/0x27b0 net/ipv4/ip_tunnel.c:843
       __gre_xmit net/ipv4/ip_gre.c:474 [inline]
       erspan_xmit+0xa9c/0x1530 net/ipv4/ip_gre.c:723
       __netdev_start_xmit include/linux/netdevice.h:5019 [inline]
       netdev_start_xmit include/linux/netdevice.h:5033 [inline]
       xmit_one net/core/dev.c:3617 [inline]
       dev_hard_start_xmit+0x298/0x7a0 net/core/dev.c:3633
       sch_direct_xmit+0x2b2/0x5e0 net/sched/sch_generic.c:342
       qdisc_restart net/sched/sch_generic.c:407 [inline]
       __qdisc_run+0xae2/0x1e90 net/sched/sch_generic.c:415
       __dev_xmit_skb net/core/dev.c:3902 [inline]
       __dev_queue_xmit+0xf0a/0x3230 net/core/dev.c:4213
       neigh_output include/net/neighbour.h:509 [inline]
       ip6_finish_output2+0xee8/0x14f0 net/ipv6/ip6_output.c:126
       dst_output include/net/dst.h:443 [inline]
       NF_HOOK include/linux/netfilter.h:302 [inline]
       rawv6_send_hdrinc+0xceb/0x1800 net/ipv6/raw.c:691
       rawv6_sendmsg+0x160e/0x2100 net/ipv6/raw.c:949
       sock_sendmsg_nosec net/socket.c:704 [inline]
       __sock_sendmsg net/socket.c:716 [inline]
       ____sys_sendmsg+0x59e/0x8f0 net/socket.c:2431
       ___sys_sendmsg+0x252/0x2e0 net/socket.c:2485
       __sys_sendmmsg+0x2bf/0x560 net/socket.c:2571
       __do_sys_sendmmsg net/socket.c:2600 [inline]
       __se_sys_sendmmsg net/socket.c:2597 [inline]
       __x64_sys_sendmmsg+0x9c/0xb0 net/socket.c:2597
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(_xmit_ETHER#2);
                               lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock);
                               lock(_xmit_ETHER#2);
  lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock);

 *** DEADLOCK ***

11 locks held by syz.3.779/6557:
 #0: ffffffff8c91fb20 (
rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
 #1: ffffffff8c91fb80 (
rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
 #2: ffffffff8c91fb80 (
rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
 #3: ffff888075660148
 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: neigh_output include/net/neighbour.h:509 [inline]
 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: ip6_finish_output2+0xee8/0x14f0 net/ipv6/ip6_output.c:126
 #4: ffff888065a97498 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
 #4: ffff888065a97498 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4429 [inline]
 #4: ffff888065a97498 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x1c0/0x5e0 net/sched/sch_generic.c:340
 #5: ffff888023b66d60 (k-slock-AF_INET6){+.-.}-{2:2}, at: spin_trylock include/linux/spinlock.h:373 [inline]
 #5: ffff888023b66d60 (k-slock-AF_INET6){+.-.}-{2:2}, at: icmpv6_xmit_lock net/ipv6/icmp.c:118 [inline]
 #5: ffff888023b66d60 (k-slock-AF_INET6){+.-.}-{2:2}, at: icmp6_send+0xcb5/0x21e0 net/ipv6/icmp.c:551
 #6: ffffffff8c91fb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
 #7: ffffffff8c91fb80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
 #8: ffffffff8c91fb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
 #9: ffffffff8c91fb80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
 #10: ffffffff8c91fb80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312

stack backtrace:
CPU: 0 PID: 6557 Comm: syz.3.779 Not tainted 5.15.164-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
 check_noncircular+0x2f8/0x3b0 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
 __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
 lock_acquire+0x1db/0x4f0 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:363 [inline]
 __dev_xmit_skb net/core/dev.c:3869 [inline]
 __dev_queue_xmit+0x2184/0x3230 net/core/dev.c:4213
 neigh_output include/net/neighbour.h:509 [inline]
 ip6_finish_output2+0xee8/0x14f0 net/ipv6/ip6_output.c:126
 dst_output include/net/dst.h:443 [inline]
 NF_HOOK include/linux/netfilter.h:302 [inline]
 ndisc_send_skb+0xae0/0x13c0 net/ipv6/ndisc.c:509
 ndisc_send_ns+0x64d/0x830 net/ipv6/ndisc.c:651
 ndisc_solicit+0x3cd/0x570
 neigh_probe net/core/neighbour.c:1017 [inline]
 __neigh_event_send+0xe8e/0x1470 net/core/neighbour.c:1178
 neigh_event_send include/net/neighbour.h:438 [inline]
 neigh_resolve_output+0x1d3/0x6d0 net/core/neighbour.c:1488
 neigh_output include/net/neighbour.h:509 [inline]
 ip6_finish_output2+0xee8/0x14f0 net/ipv6/ip6_output.c:126
 ip6_send_skb+0x12b/0x240 net/ipv6/ip6_output.c:1943
 icmp6_send+0x1732/0x21e0 net/ipv6/icmp.c:630
 __icmpv6_send include/linux/icmpv6.h:28 [inline]
 icmpv6_send include/linux/icmpv6.h:49 [inline]
 ip6_link_failure+0x37/0x4a0 net/ipv6/route.c:2794
 ip_tunnel_xmit+0x1cee/0x27b0 net/ipv4/ip_tunnel.c:843
 __gre_xmit net/ipv4/ip_gre.c:474 [inline]
 erspan_xmit+0xa9c/0x1530 net/ipv4/ip_gre.c:723
 __netdev_start_xmit include/linux/netdevice.h:5019 [inline]
 netdev_start_xmit include/linux/netdevice.h:5033 [inline]
 xmit_one net/core/dev.c:3617 [inline]
 dev_hard_start_xmit+0x298/0x7a0 net/core/dev.c:3633
 sch_direct_xmit+0x2b2/0x5e0 net/sched/sch_generic.c:342
 qdisc_restart net/sched/sch_generic.c:407 [inline]
 __qdisc_run+0xae2/0x1e90 net/sched/sch_generic.c:415
 __dev_xmit_skb net/core/dev.c:3902 [inline]
 __dev_queue_xmit+0xf0a/0x3230 net/core/dev.c:4213
 neigh_output include/net/neighbour.h:509 [inline]
 ip6_finish_output2+0xee8/0x14f0 net/ipv6/ip6_output.c:126
 dst_output include/net/dst.h:443 [inline]
 NF_HOOK include/linux/netfilter.h:302 [inline]
 rawv6_send_hdrinc+0xceb/0x1800 net/ipv6/raw.c:691
 rawv6_sendmsg+0x160e/0x2100 net/ipv6/raw.c:949
 sock_sendmsg_nosec net/socket.c:704 [inline]
 __sock_sendmsg net/socket.c:716 [inline]
 ____sys_sendmsg+0x59e/0x8f0 net/socket.c:2431
 ___sys_sendmsg+0x252/0x2e0 net/socket.c:2485
 __sys_sendmmsg+0x2bf/0x560 net/socket.c:2571
 __do_sys_sendmmsg net/socket.c:2600 [inline]
 __se_sys_sendmmsg net/socket.c:2597 [inline]
 __x64_sys_sendmmsg+0x9c/0xb0 net/socket.c:2597
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7ff50350d9f9
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:00007ff50198a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007ff5036a9f80 RCX: 00007ff50350d9f9
RDX: 0000000000000001 RSI: 0000000020001e80 RDI: 0000000000000003
RBP: 00007ff50357b8ee R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ff5036a9f80 R15: 00007fff534f4828
 </TASK>
syz.3.779 (6557) used greatest stack depth: 18904 bytes left