====================================================== WARNING: possible circular locking dependency detected 6.14.0-syzkaller-13305-g61f96e684edd #0 Not tainted ------------------------------------------------------ syz.0.13811/2513 is trying to acquire lock: ffff888053ed0a18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#2){+...}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff888053ed0a18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#2){+...}-{3:3}, at: __dev_xmit_skb net/core/dev.c:4059 [inline] ffff888053ed0a18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#2){+...}-{3:3}, at: __dev_queue_xmit+0x240a/0x3f60 net/core/dev.c:4602 but task is already holding lock: ffff88801ce8d558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff88801ce8d558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4640 [inline] ffff88801ce8d558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: sch_direct_xmit+0x1a7/0x600 net/sched/sch_generic.c:341 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+0x116/0x2f0 kernel/locking/lockdep.c:5866 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] __netif_tx_lock include/linux/netdevice.h:4640 [inline] sch_direct_xmit+0x1a7/0x600 net/sched/sch_generic.c:341 __dev_xmit_skb net/core/dev.c:4025 [inline] __dev_queue_xmit+0x1a9c/0x3f60 net/core/dev.c:4602 neigh_output include/net/neighbour.h:539 [inline] ip6_finish_output2+0x1296/0x1750 net/ipv6/ip6_output.c:141 __ip6_finish_output net/ipv6/ip6_output.c:-1 [inline] ip6_finish_output+0x421/0x840 net/ipv6/ip6_output.c:226 NF_HOOK+0xa0/0x440 include/linux/netfilter.h:314 mld_sendpack+0x84a/0xdc0 net/ipv6/mcast.c:1868 mld_send_cr net/ipv6/mcast.c:2169 [inline] mld_ifc_work+0x7d9/0xd90 net/ipv6/mcast.c:2702 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xac3/0x18e0 kernel/workqueue.c:3319 worker_thread+0x870/0xd50 kernel/workqueue.c:3400 kthread+0x7b7/0x940 kernel/kthread.c:464 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#2){+...}-{3:3}: check_prev_add kernel/locking/lockdep.c:3166 [inline] check_prevs_add kernel/locking/lockdep.c:3285 [inline] validate_chain+0xa69/0x24e0 kernel/locking/lockdep.c:3909 __lock_acquire+0xad5/0xd80 kernel/locking/lockdep.c:5235 lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] __dev_xmit_skb net/core/dev.c:4059 [inline] __dev_queue_xmit+0x240a/0x3f60 net/core/dev.c:4602 neigh_output include/net/neighbour.h:539 [inline] ip6_finish_output2+0x1296/0x1750 net/ipv6/ip6_output.c:141 __ip6_finish_output net/ipv6/ip6_output.c:-1 [inline] ip6_finish_output+0x421/0x840 net/ipv6/ip6_output.c:226 ip6_send_skb+0x1b1/0x3b0 net/ipv6/ip6_output.c:1981 icmp6_send+0x182e/0x23c0 net/ipv6/icmp.c:632 __icmpv6_send include/linux/icmpv6.h:28 [inline] icmpv6_send include/linux/icmpv6.h:49 [inline] ip6_link_failure+0x3c/0x4f0 net/ipv6/route.c:2833 ip_tunnel_xmit+0x186a/0x2560 net/ipv4/ip_tunnel.c:865 __gre_xmit+0x1d1/0x260 net/ipv4/ip_gre.c:488 erspan_xmit+0xac8/0x1320 net/ipv4/ip_gre.c:747 __netdev_start_xmit include/linux/netdevice.h:5201 [inline] netdev_start_xmit include/linux/netdevice.h:5210 [inline] xmit_one net/core/dev.c:3783 [inline] dev_hard_start_xmit+0x2d4/0x840 net/core/dev.c:3799 sch_direct_xmit+0x2b2/0x600 net/sched/sch_generic.c:343 qdisc_restart net/sched/sch_generic.c:408 [inline] __qdisc_run+0xc0d/0x2180 net/sched/sch_generic.c:416 __dev_xmit_skb net/core/dev.c:4094 [inline] __dev_queue_xmit+0x10e2/0x3f60 net/core/dev.c:4602 neigh_output include/net/neighbour.h:539 [inline] ip6_finish_output2+0x1296/0x1750 net/ipv6/ip6_output.c:141 ip6_fragment+0x1657/0x22d0 net/ipv6/ip6_output.c:1028 __ip6_finish_output net/ipv6/ip6_output.c:213 [inline] ip6_finish_output+0x2bb/0x840 net/ipv6/ip6_output.c:226 NF_HOOK include/linux/netfilter.h:314 [inline] ip6_xmit+0x1111/0x1a30 net/ipv6/ip6_output.c:366 sctp_v6_xmit+0xa62/0x14b0 net/sctp/ipv6.c:248 sctp_packet_transmit+0x26e8/0x2cd0 net/sctp/output.c:653 sctp_packet_singleton+0x22e/0x330 net/sctp/outqueue.c:783 sctp_outq_flush_ctrl net/sctp/outqueue.c:914 [inline] sctp_outq_flush+0x6d7/0x3e20 net/sctp/outqueue.c:1212 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:-1 [inline] sctp_side_effects net/sctp/sm_sideeffect.c:1198 [inline] sctp_do_sm+0x59e3/0x60e0 net/sctp/sm_sideeffect.c:1169 sctp_primitive_ASSOCIATE+0x95/0xc0 net/sctp/primitive.c:73 __sctp_connect+0xa0b/0xe60 net/sctp/socket.c:1234 __sctp_setsockopt_connectx net/sctp/socket.c:1336 [inline] sctp_getsockopt_connectx3+0x46e/0x730 net/sctp/socket.c:1421 sctp_getsockopt+0x8de/0xbb0 net/sctp/socket.c:8133 do_sock_getsockopt+0x391/0x740 net/socket.c:2357 __sys_getsockopt net/socket.c:2386 [inline] __do_sys_getsockopt net/socket.c:2393 [inline] __se_sys_getsockopt net/socket.c:2390 [inline] __x64_sys_getsockopt+0x2a3/0x370 net/socket.c:2390 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94 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#2); lock(&qdisc_xmit_lock_key#4); lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#2); *** DEADLOCK *** 10 locks held by syz.0.13811/2513: #0: ffff88808a1e5ed8 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1615 [inline] #0: ffff88808a1e5ed8 (sk_lock-AF_INET6){+.+.}-{0:0}, at: sctp_getsockopt+0x13a/0xbb0 net/sctp/socket.c:8091 #1: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #1: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] #1: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: sctp_v6_xmit+0x63a/0x14b0 net/sctp/ipv6.c:247 #2: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #2: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] #2: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: ip6_finish_output2+0x701/0x1750 net/ipv6/ip6_output.c:126 #3: ffffffff8ed3e040 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #3: ffffffff8ed3e040 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:892 [inline] #3: ffffffff8ed3e040 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x2f9/0x3f60 net/core/dev.c:4561 #4: ffff88801ce8d558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] #4: ffff88801ce8d558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4640 [inline] #4: ffff88801ce8d558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: sch_direct_xmit+0x1a7/0x600 net/sched/sch_generic.c:341 #5: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #5: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] #5: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: icmp6_send+0x281/0x23c0 net/ipv6/icmp.c:477 #6: ffff88814d0d81d8 (k-slock-AF_INET6){+.-.}-{3:3}, at: spin_trylock include/linux/spinlock.h:361 [inline] #6: ffff88814d0d81d8 (k-slock-AF_INET6){+.-.}-{3:3}, at: icmpv6_xmit_lock net/ipv6/icmp.c:108 [inline] #6: ffff88814d0d81d8 (k-slock-AF_INET6){+.-.}-{3:3}, at: icmp6_send+0xf12/0x23c0 net/ipv6/icmp.c:554 #7: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #7: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] #7: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: ip6_send_skb+0xfd/0x3b0 net/ipv6/ip6_output.c:1980 #8: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #8: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] #8: ffffffff8ed3dfe0 (rcu_read_lock){....}-{1:3}, at: ip6_finish_output2+0x701/0x1750 net/ipv6/ip6_output.c:126 #9: ffffffff8ed3e040 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #9: ffffffff8ed3e040 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:892 [inline] #9: ffffffff8ed3e040 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x2f9/0x3f60 net/core/dev.c:4561 stack backtrace: CPU: 0 UID: 0 PID: 2513 Comm: syz.0.13811 Not tainted 6.14.0-syzkaller-13305-g61f96e684edd #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2079 check_noncircular+0x142/0x160 kernel/locking/lockdep.c:2211 check_prev_add kernel/locking/lockdep.c:3166 [inline] check_prevs_add kernel/locking/lockdep.c:3285 [inline] validate_chain+0xa69/0x24e0 kernel/locking/lockdep.c:3909 __lock_acquire+0xad5/0xd80 kernel/locking/lockdep.c:5235 lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] __dev_xmit_skb net/core/dev.c:4059 [inline] __dev_queue_xmit+0x240a/0x3f60 net/core/dev.c:4602 neigh_output include/net/neighbour.h:539 [inline] ip6_finish_output2+0x1296/0x1750 net/ipv6/ip6_output.c:141 __ip6_finish_output net/ipv6/ip6_output.c:-1 [inline] ip6_finish_output+0x421/0x840 net/ipv6/ip6_output.c:226 ip6_send_skb+0x1b1/0x3b0 net/ipv6/ip6_output.c:1981 icmp6_send+0x182e/0x23c0 net/ipv6/icmp.c:632 __icmpv6_send include/linux/icmpv6.h:28 [inline] icmpv6_send include/linux/icmpv6.h:49 [inline] ip6_link_failure+0x3c/0x4f0 net/ipv6/route.c:2833 ip_tunnel_xmit+0x186a/0x2560 net/ipv4/ip_tunnel.c:865 __gre_xmit+0x1d1/0x260 net/ipv4/ip_gre.c:488 erspan_xmit+0xac8/0x1320 net/ipv4/ip_gre.c:747 __netdev_start_xmit include/linux/netdevice.h:5201 [inline] netdev_start_xmit include/linux/netdevice.h:5210 [inline] xmit_one net/core/dev.c:3783 [inline] dev_hard_start_xmit+0x2d4/0x840 net/core/dev.c:3799 sch_direct_xmit+0x2b2/0x600 net/sched/sch_generic.c:343 qdisc_restart net/sched/sch_generic.c:408 [inline] __qdisc_run+0xc0d/0x2180 net/sched/sch_generic.c:416 __dev_xmit_skb net/core/dev.c:4094 [inline] __dev_queue_xmit+0x10e2/0x3f60 net/core/dev.c:4602 neigh_output include/net/neighbour.h:539 [inline] ip6_finish_output2+0x1296/0x1750 net/ipv6/ip6_output.c:141 ip6_fragment+0x1657/0x22d0 net/ipv6/ip6_output.c:1028 __ip6_finish_output net/ipv6/ip6_output.c:213 [inline] ip6_finish_output+0x2bb/0x840 net/ipv6/ip6_output.c:226 NF_HOOK include/linux/netfilter.h:314 [inline] ip6_xmit+0x1111/0x1a30 net/ipv6/ip6_output.c:366 sctp_v6_xmit+0xa62/0x14b0 net/sctp/ipv6.c:248 sctp_packet_transmit+0x26e8/0x2cd0 net/sctp/output.c:653 sctp_packet_singleton+0x22e/0x330 net/sctp/outqueue.c:783 sctp_outq_flush_ctrl net/sctp/outqueue.c:914 [inline] sctp_outq_flush+0x6d7/0x3e20 net/sctp/outqueue.c:1212 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:-1 [inline] sctp_side_effects net/sctp/sm_sideeffect.c:1198 [inline] sctp_do_sm+0x59e3/0x60e0 net/sctp/sm_sideeffect.c:1169 sctp_primitive_ASSOCIATE+0x95/0xc0 net/sctp/primitive.c:73 __sctp_connect+0xa0b/0xe60 net/sctp/socket.c:1234 __sctp_setsockopt_connectx net/sctp/socket.c:1336 [inline] sctp_getsockopt_connectx3+0x46e/0x730 net/sctp/socket.c:1421 sctp_getsockopt+0x8de/0xbb0 net/sctp/socket.c:8133 do_sock_getsockopt+0x391/0x740 net/socket.c:2357 __sys_getsockopt net/socket.c:2386 [inline] __do_sys_getsockopt net/socket.c:2393 [inline] __se_sys_getsockopt net/socket.c:2390 [inline] __x64_sys_getsockopt+0x2a3/0x370 net/socket.c:2390 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f99cf18d169 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:00007f99cfeff038 EFLAGS: 00000246 ORIG_RAX: 0000000000000037 RAX: ffffffffffffffda RBX: 00007f99cf3a5fa0 RCX: 00007f99cf18d169 RDX: 000000000000006f RSI: 0000000000000084 RDI: 0000000000000003 RBP: 00007f99cf20e2a0 R08: 0000200000000440 R09: 0000000000000000 R10: 0000200000000080 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f99cf3a5fa0 R15: 00007fffafe4afc8 syz.0.13811 (2513) used greatest stack depth: 17584 bytes left