syzbot

EXT4-fs (loop4): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback.
ext4 filesystem being mounted at /478/file0 supports timestamps until 2038-01-19 (0x7fffffff)
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BUG: KCSAN: data-race in snd_seq_fifo_cell_out / snd_seq_fifo_poll_wait

read-write to 0xffff8881184a5eb8 of 4 bytes by task 10533 on cpu 0:
 fifo_cell_out sound/core/seq/seq_fifo.c:153 [inline]
 snd_seq_fifo_cell_out+0x222/0x270 sound/core/seq/seq_fifo.c:173
 snd_seq_read+0x1c8/0x410 sound/core/seq/seq_clientmgr.c:478
 loop_rw_iter+0x2c3/0x3f0 include/linux/uio.h:-1
 io_iter_do_read io_uring/rw.c:830 [inline]
 __io_read+0xbcb/0xc20 io_uring/rw.c:941
 io_read+0x1c/0x60 io_uring/rw.c:1020
 __io_issue_sqe+0xfb/0x2e0 io_uring/io_uring.c:1773
 io_issue_sqe+0x53/0x970 io_uring/io_uring.c:1796
 io_wq_submit_work+0x3f7/0x5f0 io_uring/io_uring.c:1908
 io_worker_handle_work+0x44e/0x9b0 io_uring/io-wq.c:642
 io_wq_worker+0x22e/0x870 io_uring/io-wq.c:696
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff8881184a5eb8 of 4 bytes by task 10526 on cpu 1:
 snd_seq_fifo_poll_wait+0x68/0x90 sound/core/seq/seq_fifo.c:216
 snd_seq_poll+0xa1/0x140 sound/core/seq/seq_clientmgr.c:1160
 vfs_poll include/linux/poll.h:82 [inline]
 io_file_supports_nowait io_uring/rw.c:46 [inline]
 __io_read+0x2e7/0xc20 io_uring/rw.c:927
 io_read+0x1c/0x60 io_uring/rw.c:1020
 __io_issue_sqe+0xfb/0x2e0 io_uring/io_uring.c:1773
 io_issue_sqe+0x53/0x970 io_uring/io_uring.c:1796
 io_queue_sqe io_uring/io_uring.c:2025 [inline]
 io_req_task_submit+0x6b/0xd0 io_uring/io_uring.c:1415
 io_handle_tw_list+0x18d/0x1c0 io_uring/io_uring.c:1102
 tctx_task_work_run+0x6d/0x1a0 io_uring/io_uring.c:1167
 tctx_task_work+0x3f/0x80 io_uring/io_uring.c:1185
 task_work_run+0x12e/0x1a0 kernel/task_work.c:227
 get_signal+0xe13/0xf70 kernel/signal.c:2807
 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x7a/0x100 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+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 10526 Comm: syz.4.2244 Not tainted 6.17.0-rc1-syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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