======================================================
WARNING: possible circular locking dependency detected
6.17.0-rc1-syzkaller-00036-gdfc0f6373094 #0 Not tainted
------------------------------------------------------
syz.1.5205/23783 is trying to acquire lock:
ffff888027b70218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: __dev_queue_xmit+0x22b7/0x3b50

but task is already holding lock:
ffff888027d8f558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: sch_direct_xmit+0x153/0x4b0

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}:
       lock_acquire+0x120/0x360
       _raw_spin_lock+0x2e/0x40
       sch_direct_xmit+0x153/0x4b0
       __dev_queue_xmit+0x1857/0x3b50
       ip6_finish_output2+0x11fe/0x16a0
       NF_HOOK+0x9e/0x380
       mld_sendpack+0x800/0xd80
       mld_ifc_work+0x83e/0xd60
       process_scheduled_works+0xae1/0x17b0
       worker_thread+0x8a0/0xda0
       kthread+0x711/0x8a0
       ret_from_fork+0x3fc/0x770
       ret_from_fork_asm+0x1a/0x30

-> #0 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}:
       validate_chain+0xb9b/0x2140
       __lock_acquire+0xab9/0xd20
       lock_acquire+0x120/0x360
       _raw_spin_lock+0x2e/0x40
       __dev_queue_xmit+0x22b7/0x3b50
       ip6_finish_output2+0x11fe/0x16a0
       ip6_send_skb+0x1d5/0x390
       icmp6_send+0x12c6/0x1940
       ip6_link_failure+0x3b/0x4c0
       ip_tunnel_xmit+0x175b/0x2390
       __gre_xmit+0x19a/0x240
       erspan_xmit+0xa04/0x1220
       dev_hard_start_xmit+0x2d7/0x830
       sch_direct_xmit+0x241/0x4b0
       __qdisc_run+0xb16/0x15f0
       __dev_queue_xmit+0x1056/0x3b50
       ip6_finish_output2+0x11fe/0x16a0
       ip6_xmit+0x107a/0x1840
       sctp_v6_xmit+0xa33/0x1300
       sctp_packet_transmit+0x2581/0x2bb0
       sctp_packet_singleton+0x233/0x330
       sctp_outq_flush+0x4f0/0x3140
       sctp_do_sm+0x5332/0x5a20
       sctp_primitive_ASSOCIATE+0x95/0xc0
       sctp_sendmsg_to_asoc+0x102d/0x1810
       sctp_sendmsg+0x1941/0x2810
       __sock_sendmsg+0x19c/0x270
       ____sys_sendmsg+0x52d/0x830
       ___sys_sendmsg+0x21f/0x2a0
       __sys_sendmmsg+0x227/0x430
       __x64_sys_sendmmsg+0xa0/0xc0
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&qdisc_xmit_lock_key#4);
                               lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3);
                               lock(&qdisc_xmit_lock_key#4);
  lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3);

 *** DEADLOCK ***

10 locks held by syz.1.5205/23783:
 #0: ffff888112c33b58 (sk_lock-AF_INET6){+.+.}-{0:0}, at: sctp_sendmsg+0xb97/0x2810
 #1: ffffffff8e139ee0 (rcu_read_lock){....}-{1:3}, at: sctp_v6_xmit+0x60f/0x1300
 #2: ffffffff8e139ee0 (rcu_read_lock){....}-{1:3}, at: ip6_finish_output2+0x701/0x16a0
 #3: ffffffff8e139f40 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x27b/0x3b50
 #4: ffff888027d8f558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: sch_direct_xmit+0x153/0x4b0
 #5: ffffffff8e139ee0 (rcu_read_lock){....}-{1:3}, at: icmp6_send+0x1e9/0x1940
 #6: ffff8881089381d8 (k-slock-AF_INET6){+.-.}-{3:3}, at: icmp6_send+0xc5c/0x1940
 #7: ffffffff8e139ee0 (rcu_read_lock){....}-{1:3}, at: ip6_send_skb+0x10f/0x390
 #8: ffffffff8e139ee0 (rcu_read_lock){....}-{1:3}, at: ip6_finish_output2+0x701/0x16a0
 #9: ffffffff8e139f40 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x27b/0x3b50

stack backtrace:
CPU: 0 UID: 0 PID: 23783 Comm: syz.1.5205 Not tainted 6.17.0-rc1-syzkaller-00036-gdfc0f6373094 #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_circular_bug+0x2ee/0x310
 check_noncircular+0x134/0x160
 validate_chain+0xb9b/0x2140
 __lock_acquire+0xab9/0xd20
 lock_acquire+0x120/0x360
 _raw_spin_lock+0x2e/0x40
 __dev_queue_xmit+0x22b7/0x3b50
 ip6_finish_output2+0x11fe/0x16a0
 ip6_send_skb+0x1d5/0x390
 icmp6_send+0x12c6/0x1940
 ip6_link_failure+0x3b/0x4c0
 ip_tunnel_xmit+0x175b/0x2390
 __gre_xmit+0x19a/0x240
 erspan_xmit+0xa04/0x1220
 dev_hard_start_xmit+0x2d7/0x830
 sch_direct_xmit+0x241/0x4b0
 __qdisc_run+0xb16/0x15f0
 __dev_queue_xmit+0x1056/0x3b50
 ip6_finish_output2+0x11fe/0x16a0
 ip6_xmit+0x107a/0x1840
 sctp_v6_xmit+0xa33/0x1300
 sctp_packet_transmit+0x2581/0x2bb0
 sctp_packet_singleton+0x233/0x330
 sctp_outq_flush+0x4f0/0x3140
 sctp_do_sm+0x5332/0x5a20
 sctp_primitive_ASSOCIATE+0x95/0xc0
 sctp_sendmsg_to_asoc+0x102d/0x1810
 sctp_sendmsg+0x1941/0x2810
 __sock_sendmsg+0x19c/0x270
 ____sys_sendmsg+0x52d/0x830
 ___sys_sendmsg+0x21f/0x2a0
 __sys_sendmmsg+0x227/0x430
 __x64_sys_sendmmsg+0xa0/0xc0
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f509598ebe9
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:00007f5096878038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f5095bb5fa0 RCX: 00007f509598ebe9
RDX: 0000000000000002 RSI: 0000200000003440 RDI: 0000000000000003
RBP: 00007f5095a11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5095bb6038 R14: 00007f5095bb5fa0 R15: 00007fff78220e18
 </TASK>
syz.1.5205 (23783) used greatest stack depth: 17416 bytes left
