====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.2.11635/14893 is trying to acquire lock: ffff8880327c0f30 (&hsr->seqnr_lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] ffff8880327c0f30 (&hsr->seqnr_lock){+.-.}-{3:3}, at: hsr_dev_xmit+0x237/0x360 net/hsr/hsr_device.c:235 but task is already holding lock: ffff88802f95d158 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff88802f95d158 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4685 [inline] ffff88802f95d158 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __dev_queue_xmit+0x1676/0x3b50 net/core/dev.c:4759 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 kernel/locking/lockdep.c:5868 __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:4685 [inline] sch_direct_xmit+0x153/0x4b0 net/sched/sch_generic.c:345 __dev_xmit_skb net/core/dev.c:4152 [inline] __dev_queue_xmit+0x1857/0x3b50 net/core/dev.c:4729 dev_queue_xmit include/linux/netdevice.h:3365 [inline] hsr_xmit net/hsr/hsr_forward.c:438 [inline] hsr_forward_do net/hsr/hsr_forward.c:579 [inline] hsr_forward_skb+0x158b/0x2860 net/hsr/hsr_forward.c:741 send_hsr_supervision_frame+0x731/0xcb0 net/hsr/hsr_device.c:364 hsr_announce+0x1d5/0x360 net/hsr/hsr_device.c:421 call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1748 expire_timers kernel/time/timer.c:1799 [inline] __run_timers kernel/time/timer.c:2373 [inline] __run_timer_base+0x61a/0x860 kernel/time/timer.c:2385 run_timer_base kernel/time/timer.c:2394 [inline] run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2404 handle_softirqs+0x286/0x870 kernel/softirq.c:622 __do_softirq kernel/softirq.c:656 [inline] invoke_softirq kernel/softirq.c:496 [inline] __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:723 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline] sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1052 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 rcu_is_watching_curr_cpu include/linux/context_tracking.h:-1 [inline] rcu_is_watching+0x26/0xb0 kernel/rcu/tree.c:751 rcu_read_lock include/linux/rcupdate.h:868 [inline] class_rcu_constructor include/linux/rcupdate.h:1195 [inline] unwind_next_frame+0xd4/0x2390 arch/x86/kernel/unwind_orc.c:479 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:56 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:559 __call_rcu_common kernel/rcu/tree.c:3123 [inline] call_rcu+0x157/0x9c0 kernel/rcu/tree.c:3243 slab_free_hook mm/slub.c:2507 [inline] slab_free mm/slub.c:6642 [inline] kmem_cache_free+0x4b5/0x690 mm/slub.c:6752 exit_mmap+0x537/0xb40 mm/mmap.c:1305 __mmput+0x118/0x430 kernel/fork.c:1133 exit_mm+0x1da/0x2c0 kernel/exit.c:582 do_exit+0x648/0x2300 kernel/exit.c:954 do_group_exit+0x21c/0x2d0 kernel/exit.c:1107 get_signal+0x1285/0x1340 kernel/signal.c:3034 arch_do_signal_or_restart+0xa0/0x790 arch/x86/kernel/signal.c:337 exit_to_user_mode_loop+0x72/0x130 kernel/entry/common.c:40 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline] syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline] do_syscall_64+0x2bd/0xfa0 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&hsr->seqnr_lock){+.-.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:356 [inline] hsr_dev_xmit+0x237/0x360 net/hsr/hsr_device.c:235 __netdev_start_xmit include/linux/netdevice.h:5248 [inline] netdev_start_xmit include/linux/netdevice.h:5257 [inline] xmit_one net/core/dev.c:3845 [inline] dev_hard_start_xmit+0x2d7/0x830 net/core/dev.c:3861 __dev_queue_xmit+0x1b8d/0x3b50 net/core/dev.c:4763 NF_HOOK+0x310/0x3a0 include/linux/netfilter.h:-1 arp_xmit+0x16c/0x270 net/ipv4/arp.c:664 arp_solicit+0xc1d/0xe60 net/ipv4/arp.c:392 neigh_probe net/core/neighbour.c:1098 [inline] __neigh_event_send+0xf70/0x1560 net/core/neighbour.c:1271 neigh_event_send_probe include/net/neighbour.h:471 [inline] neigh_event_send include/net/neighbour.h:477 [inline] neigh_resolve_output+0x198/0x750 net/core/neighbour.c:1579 neigh_output include/net/neighbour.h:547 [inline] ip_finish_output2+0xd40/0x1160 net/ipv4/ip_output.c:237 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip_output+0x29f/0x450 net/ipv4/ip_output.c:438 iptunnel_xmit+0x5f8/0xa90 net/ipv4/ip_tunnel_core.c:84 ip_tunnel_xmit+0x1c41/0x2390 net/ipv4/ip_tunnel.c:845 __gre_xmit net/ipv4/ip_gre.c:488 [inline] ipgre_xmit+0x89e/0xc50 net/ipv4/ip_gre.c:692 __netdev_start_xmit include/linux/netdevice.h:5248 [inline] netdev_start_xmit include/linux/netdevice.h:5257 [inline] xmit_one net/core/dev.c:3845 [inline] dev_hard_start_xmit+0x2d7/0x830 net/core/dev.c:3861 __dev_queue_xmit+0x1b8d/0x3b50 net/core/dev.c:4763 packet_snd net/packet/af_packet.c:3076 [inline] packet_sendmsg+0x3e33/0x5080 net/packet/af_packet.c:3108 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg+0x21c/0x270 net/socket.c:742 __sys_sendto+0x3bd/0x520 net/socket.c:2244 __do_sys_sendto net/socket.c:2251 [inline] __se_sys_sendto net/socket.c:2247 [inline] __x64_sys_sendto+0xde/0x100 net/socket.c:2247 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 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(&hsr->seqnr_lock); lock(&qdisc_xmit_lock_key#4); lock(&hsr->seqnr_lock); *** DEADLOCK *** 7 locks held by syz.2.11635/14893: #0: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #0: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:918 [inline] #0: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x27b/0x3b50 net/core/dev.c:4688 #1: ffff88802f95d158 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] #1: ffff88802f95d158 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4685 [inline] #1: ffff88802f95d158 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __dev_queue_xmit+0x1676/0x3b50 net/core/dev.c:4759 #2: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #2: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #2: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: ip_output+0x5b/0x450 net/ipv4/ip_output.c:433 #3: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #3: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #3: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: ip_finish_output2+0x452/0x1160 net/ipv4/ip_output.c:230 #4: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #4: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #4: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: arp_xmit+0x23/0x270 net/ipv4/arp.c:662 #5: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #5: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:918 [inline] #5: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x27b/0x3b50 net/core/dev.c:4688 #6: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #6: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #6: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: hsr_dev_xmit+0x2d/0x360 net/hsr/hsr_device.c:229 stack backtrace: CPU: 0 UID: 0 PID: 14893 Comm: syz.2.11635 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:356 [inline] hsr_dev_xmit+0x237/0x360 net/hsr/hsr_device.c:235 __netdev_start_xmit include/linux/netdevice.h:5248 [inline] netdev_start_xmit include/linux/netdevice.h:5257 [inline] xmit_one net/core/dev.c:3845 [inline] dev_hard_start_xmit+0x2d7/0x830 net/core/dev.c:3861 __dev_queue_xmit+0x1b8d/0x3b50 net/core/dev.c:4763 NF_HOOK+0x310/0x3a0 include/linux/netfilter.h:-1 arp_xmit+0x16c/0x270 net/ipv4/arp.c:664 arp_solicit+0xc1d/0xe60 net/ipv4/arp.c:392 neigh_probe net/core/neighbour.c:1098 [inline] __neigh_event_send+0xf70/0x1560 net/core/neighbour.c:1271 neigh_event_send_probe include/net/neighbour.h:471 [inline] neigh_event_send include/net/neighbour.h:477 [inline] neigh_resolve_output+0x198/0x750 net/core/neighbour.c:1579 neigh_output include/net/neighbour.h:547 [inline] ip_finish_output2+0xd40/0x1160 net/ipv4/ip_output.c:237 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip_output+0x29f/0x450 net/ipv4/ip_output.c:438 iptunnel_xmit+0x5f8/0xa90 net/ipv4/ip_tunnel_core.c:84 ip_tunnel_xmit+0x1c41/0x2390 net/ipv4/ip_tunnel.c:845 __gre_xmit net/ipv4/ip_gre.c:488 [inline] ipgre_xmit+0x89e/0xc50 net/ipv4/ip_gre.c:692 __netdev_start_xmit include/linux/netdevice.h:5248 [inline] netdev_start_xmit include/linux/netdevice.h:5257 [inline] xmit_one net/core/dev.c:3845 [inline] dev_hard_start_xmit+0x2d7/0x830 net/core/dev.c:3861 __dev_queue_xmit+0x1b8d/0x3b50 net/core/dev.c:4763 packet_snd net/packet/af_packet.c:3076 [inline] packet_sendmsg+0x3e33/0x5080 net/packet/af_packet.c:3108 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg+0x21c/0x270 net/socket.c:742 __sys_sendto+0x3bd/0x520 net/socket.c:2244 __do_sys_sendto net/socket.c:2251 [inline] __se_sys_sendto net/socket.c:2247 [inline] __x64_sys_sendto+0xde/0x100 net/socket.c:2247 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fe2baf8f749 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:00007fe2b91f6038 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007fe2bb1e5fa0 RCX: 00007fe2baf8f749 RDX: 0000000000000086 RSI: 0000200000000240 RDI: 0000000000000003 RBP: 00007fe2bb013f91 R08: 0000200000000540 R09: 0000000000000014 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fe2bb1e6038 R14: 00007fe2bb1e5fa0 R15: 00007ffc5e42e9d8