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BUG: KCSAN: data-race in snd_seq_check_queue / snd_seq_control_queue

write to 0xffff888079b851e4 of 1 bytes by interrupt on cpu 0:
 snd_seq_check_queue+0x251/0x290 sound/core/seq/seq_queue.c:283
 snd_seq_timer_interrupt+0x228/0x240 sound/core/seq/seq_timer.c:158
 snd_timer_process_callbacks sound/core/timer.c:796 [inline]
 snd_timer_interrupt+0xa7c/0xb50 sound/core/timer.c:919
 snd_hrtimer_callback+0x13a/0x220 sound/core/hrtimer.c:50
 __run_hrtimer+0x154/0x4b0 kernel/time/hrtimer.c:1524
 __hrtimer_run_queues kernel/time/hrtimer.c:1588 [inline]
 hrtimer_interrupt+0x37c/0xa40 kernel/time/hrtimer.c:1650
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1080 [inline]
 __sysvec_apic_timer_interrupt+0xa3/0x280 arch/x86/kernel/apic/apic.c:1097
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 sysvec_apic_timer_interrupt+0x80/0xd0 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:581
 check_access kernel/kcsan/core.c:605 [inline]
 __tsan_read8+0x15a/0x180 kernel/kcsan/core.c:801
 skb_network_header include/linux/skbuff.h:2517 [inline]
 ipv6_hdr include/linux/ipv6.h:95 [inline]
 br_validate_ipv6+0xb1/0x6f0 net/bridge/br_netfilter_ipv6.c:112
 br_nf_pre_routing_ipv6+0x41/0x280 net/bridge/br_netfilter_ipv6.c:221
 br_nf_pre_routing+0x4d6/0xb40 net/bridge/br_netfilter_hooks.c:505
 nf_hook_entry_hookfn include/linux/netfilter.h:136 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:228 [inline]
 br_handle_frame+0x413/0xb10 net/bridge/br_input.c:356
 __netif_receive_skb_core+0xea9/0x1da0 net/core/dev.c:5180
 __netif_receive_skb_one_core net/core/dev.c:5284 [inline]
 __netif_receive_skb+0x52/0x1b0 net/core/dev.c:5400
 process_backlog+0x29f/0x4a0 net/core/dev.c:6242
 napi_poll+0x178/0x4f0 net/core/dev.c:6688
 net_rx_action+0x1ba/0x530 net/core/dev.c:6758
 __do_softirq+0x198/0x360 kernel/softirq.c:298
 run_ksoftirqd+0x2f/0x60 kernel/softirq.c:652
 smpboot_thread_fn+0x347/0x530 kernel/smpboot.c:165
 kthread+0x20d/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff888079b851e4 of 1 bytes by task 14445 on cpu 1:
 queue_access_unlock sound/core/seq/seq_queue.c:370 [inline]
 snd_seq_control_queue+0x4f2/0x550 sound/core/seq/seq_queue.c:734
 event_input_timer+0x1e/0x30 sound/core/seq/seq_system.c:103
 snd_seq_deliver_single_event+0x31b/0x4f0 sound/core/seq/seq_clientmgr.c:638
 snd_seq_deliver_event+0x192/0x4a0 sound/core/seq/seq_clientmgr.c:839
 snd_seq_dispatch_event+0x14c/0x270 sound/core/seq/seq_clientmgr.c:913
 snd_seq_check_queue+0xfe/0x290 sound/core/seq/seq_queue.c:264
 snd_seq_enqueue_event+0x275/0x2b0 sound/core/seq/seq_queue.c:333
 snd_seq_client_enqueue_event+0x206/0x2a0 sound/core/seq/seq_clientmgr.c:974
 snd_seq_write+0x435/0x550 sound/core/seq/seq_clientmgr.c:1093
 vfs_write+0x1df/0x6f0 fs/read_write.c:576
 ksys_write+0xce/0x180 fs/read_write.c:631
 __do_sys_write fs/read_write.c:643 [inline]
 __se_sys_write fs/read_write.c:640 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:640
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14445 Comm: syz-executor.4 Not tainted 5.9.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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