[syzbot] [sound?] KCSAN: data-race in snd_seq_poll / snd_seq_pool_init

syzbot
2025-03-05T17:25:24Z

Hello,

syzbot found the following issue on:

HEAD commit: 48a5eed9ad58 Merge tag 'devicetree-fixes-for-6.14-2' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1657d8b7980000
kernel config: https://syzkaller.appspot.com/x/.config?x=523b0e2f15224775
dashboard link: https://syzkaller.appspot.com/bug?extid=2d373c9936c00d7e120c
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/877a63ac53f2/disk-48a5eed9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7b3a614d4df6/vmlinux-48a5eed9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2ce987fd9e0c/bzImage-48a5eed9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2d373c9936c00d7e120c@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in snd_seq_poll / snd_seq_pool_init

write to 0xffff888114535610 of 4 bytes by task 7006 on cpu 1:
snd_seq_pool_init+0x1c1/0x200 sound/core/seq/seq_memory.c:469
snd_seq_write+0x17f/0x500 sound/core/seq/seq_clientmgr.c:1022
vfs_write+0x27d/0x920 fs/read_write.c:677
ksys_write+0xe8/0x1b0 fs/read_write.c:731
__do_sys_write fs/read_write.c:742 [inline]
__se_sys_write fs/read_write.c:739 [inline]
__x64_sys_write+0x42/0x50 fs/read_write.c:739
x64_sys_call+0x287e/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:2
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888114535610 of 4 bytes by task 7005 on cpu 0:
snd_seq_total_cells sound/core/seq/seq_memory.h:83 [inline]
snd_seq_write_pool_allocated sound/core/seq/seq_clientmgr.c:95 [inline]
snd_seq_poll+0x103/0x170 sound/core/seq/seq_clientmgr.c:1139
vfs_poll include/linux/poll.h:82 [inline]
__io_arm_poll_handler+0x1e5/0xd50 io_uring/poll.c:582
io_arm_poll_handler+0x464/0x5b0 io_uring/poll.c:707
io_queue_async+0x89/0x320 io_uring/io_uring.c:1925
io_queue_sqe io_uring/io_uring.c:1954 [inline]
io_req_task_submit+0xb9/0xc0 io_uring/io_uring.c:1373
io_handle_tw_list+0x1b9/0x200 io_uring/io_uring.c:1059
tctx_task_work_run+0x6e/0x1c0 io_uring/io_uring.c:1123
tctx_task_work+0x40/0x80 io_uring/io_uring.c:1141
task_work_run+0x13a/0x1a0 kernel/task_work.c:227
get_signal+0xe78/0x1000 kernel/signal.c:2809
arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x62/0x120 kernel/entry/common.c:218
do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000 -> 0x000001f4

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 7005 Comm: syz.2.1455 Tainted: G W 6.14.0-rc5-syzkaller-00016-g48a5eed9ad58 #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
==================================================================

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