============================================ WARNING: possible recursive locking detected syzkaller #0 Tainted: G L -------------------------------------------- kworker/2:7/12083 is trying to acquire lock: ffff8880331f8558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline] ffff8880331f8558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4781 [inline] ffff8880331f8558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: sch_direct_xmit+0x3b5/0xc60 net/sched/sch_generic.c:370 but task is already holding lock: ffff88802ff16558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline] ffff88802ff16558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4781 [inline] ffff88802ff16558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: sch_direct_xmit+0x3b5/0xc60 net/sched/sch_generic.c:370 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&qdisc_xmit_lock_key#4); lock(&qdisc_xmit_lock_key#4); *** DEADLOCK *** May be due to missing lock nesting notation 13 locks held by kworker/2:7/12083: #0: ffff888036ea4540 ((wq_completion)mld){+.+.}-{0:0}, at: process_one_work+0x12d6/0x1980 kernel/workqueue.c:3289 #1: ffffc9000cb7fd08 ((work_completion)(&(&idev->mc_ifc_work)->work)){+.+.}-{0:0}, at: process_one_work+0x973/0x1980 kernel/workqueue.c:3290 #2: ffff8880566c0530 (&idev->mc_lock){+.+.}-{4:4}, at: mld_ifc_work+0x42/0xc10 net/ipv6/mcast.c:2692 #3: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #3: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #3: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: mld_sendpack+0x1b5/0xec0 net/ipv6/mcast.c:1827 #4: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #4: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #4: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: ip6_output+0x135/0xa60 net/ipv6/ip6_output.c:234 #5: ffffffff8e7e5500 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #5: ffffffff8e7e5500 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:891 [inline] #5: ffffffff8e7e5500 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x296/0x4950 net/core/dev.c:4791 #6: ffff88802ddad228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: spin_trylock include/linux/spinlock.h:354 [inline] #6: ffff88802ddad228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: qdisc_run_begin include/net/sch_generic.h:205 [inline] #6: ffff88802ddad228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: __dev_xmit_skb net/core/dev.c:4196 [inline] #6: ffff88802ddad228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: __dev_queue_xmit+0x24ef/0x4950 net/core/dev.c:4831 #7: ffff88802ff16558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline] #7: ffff88802ff16558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4781 [inline] #7: ffff88802ff16558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: sch_direct_xmit+0x3b5/0xc60 net/sched/sch_generic.c:370 #8: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #8: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #8: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: ip_output+0xb3/0xc10 net/ipv4/ip_output.c:433 #9: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #9: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #9: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: ip_finish_output2+0x356/0x2400 net/ipv4/ip_output.c:230 #10: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #10: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #10: ffffffff8e7e5560 (rcu_read_lock){....}-{1:3}, at: arp_xmit+0x26/0x2e0 net/ipv4/arp.c:663 #11: ffffffff8e7e5500 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #11: ffffffff8e7e5500 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:891 [inline] #11: ffffffff8e7e5500 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x296/0x4950 net/core/dev.c:4791 #12: ffff88803c4ea228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: spin_trylock include/linux/spinlock.h:354 [inline] #12: ffff88803c4ea228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: qdisc_run_begin include/net/sch_generic.h:205 [inline] #12: ffff88803c4ea228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: __dev_xmit_skb net/core/dev.c:4196 [inline] #12: ffff88803c4ea228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: __dev_queue_xmit+0x24ef/0x4950 net/core/dev.c:4831 stack backtrace: CPU: 2 UID: 0 PID: 12083 Comm: kworker/2:7 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Workqueue: mld mld_ifc_work Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_deadlock_bug.cold+0xbd/0xca kernel/locking/lockdep.c:3041 check_deadlock kernel/locking/lockdep.c:3093 [inline] validate_chain kernel/locking/lockdep.c:3895 [inline] __lock_acquire+0x12bb/0x2630 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b1/0x370 kernel/locking/lockdep.c:5825 __raw_spin_lock include/linux/spinlock_api_smp.h:158 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:158 spin_lock include/linux/spinlock.h:342 [inline] __netif_tx_lock include/linux/netdevice.h:4781 [inline] sch_direct_xmit+0x3b5/0xc60 net/sched/sch_generic.c:370 __dev_xmit_skb net/core/dev.c:4209 [inline] __dev_queue_xmit+0x2794/0x4950 net/core/dev.c:4831 dev_queue_xmit include/linux/netdevice.h:3418 [inline] arp_xmit_finish net/ipv4/arp.c:655 [inline] NF_HOOK include/linux/netfilter.h:318 [inline] NF_HOOK include/linux/netfilter.h:312 [inline] arp_xmit+0x106/0x2e0 net/ipv4/arp.c:665 arp_send_dst net/ipv4/arp.c:320 [inline] arp_send_dst+0x200/0x280 net/ipv4/arp.c:301 arp_solicit+0x672/0x1070 net/ipv4/arp.c:392 neigh_probe+0xce/0x110 net/core/neighbour.c:1096 __neigh_event_send+0xacf/0x13f0 net/core/neighbour.c:1276 neigh_event_send_probe include/net/neighbour.h:480 [inline] neigh_event_send include/net/neighbour.h:486 [inline] neigh_event_send include/net/neighbour.h:484 [inline] neigh_resolve_output+0x550/0x8f0 net/core/neighbour.c:1603 neigh_output include/net/neighbour.h:560 [inline] ip_finish_output2+0x851/0x2400 net/ipv4/ip_output.c:237 __ip_finish_output.part.0+0x444/0x6f0 net/ipv4/ip_output.c:315 __ip_finish_output net/ipv4/ip_output.c:303 [inline] ip_finish_output net/ipv4/ip_output.c:325 [inline] NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip_output+0x39b/0xc10 net/ipv4/ip_output.c:438 dst_output include/net/dst.h:470 [inline] ip_local_out+0x193/0x1f0 net/ipv4/ip_output.c:131 iptunnel_xmit+0x722/0xd20 net/ipv4/ip_tunnel_core.c:97 ip_tunnel_xmit+0x1b85/0x3200 net/ipv4/ip_tunnel.c:845 __gre_xmit+0x820/0xb20 net/ipv4/ip_gre.c:491 erspan_xmit+0x55a/0x1ec0 net/ipv4/ip_gre.c:750 __netdev_start_xmit include/linux/netdevice.h:5368 [inline] netdev_start_xmit include/linux/netdevice.h:5377 [inline] xmit_one net/core/dev.c:3888 [inline] dev_hard_start_xmit+0x128/0x7a0 net/core/dev.c:3904 sch_direct_xmit+0x1b2/0xc60 net/sched/sch_generic.c:372 __dev_xmit_skb net/core/dev.c:4209 [inline] __dev_queue_xmit+0x2794/0x4950 net/core/dev.c:4831 dev_queue_xmit include/linux/netdevice.h:3418 [inline] neigh_resolve_output net/core/neighbour.c:1619 [inline] neigh_resolve_output+0x51f/0x8f0 net/core/neighbour.c:1599 neigh_output include/net/neighbour.h:560 [inline] ip6_finish_output2+0xb0f/0x1ce0 net/ipv6/ip6_output.c:136 __ip6_finish_output+0x357/0xdf0 net/ipv6/ip6_output.c:208 ip6_finish_output net/ipv6/ip6_output.c:219 [inline] NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x2aa/0xa60 net/ipv6/ip6_output.c:246 dst_output include/net/dst.h:470 [inline] NF_HOOK include/linux/netfilter.h:318 [inline] NF_HOOK.constprop.0+0x115/0x5a0 include/linux/netfilter.h:312 mld_sendpack+0x8f7/0xec0 net/ipv6/mcast.c:1855 mld_send_cr net/ipv6/mcast.c:2154 [inline] mld_ifc_work+0x75a/0xc10 net/ipv6/mcast.c:2693 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3314 process_scheduled_works kernel/workqueue.c:3397 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478 kthread+0x370/0x450 kernel/kthread.c:436 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245