KCSAN: data-race in snd_seq_cell_alloc / snd_seq_info_pool (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f01c30de Merge tag 'vfs-5.10-fixes-2' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13b78dba500000
kernel config: https://syzkaller.appspot.com/x/.config?x=671e27f23e60a67b
dashboard link: https://syzkaller.appspot.com/bug?extid=db8ae45a45481e1b83a3
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [alsa-...@alsa-project.org linux-...@vger.kernel.org pe...@perex.cz ti...@suse.com]

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+db8ae4...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in snd_seq_cell_alloc / snd_seq_info_pool

read-write to 0xffff8880273e71b0 of 4 bytes by task 29607 on cpu 0:
snd_seq_cell_alloc+0x2f1/0x350 sound/core/seq/seq_memory.c:260
snd_seq_event_dup+0xe0/0x400 sound/core/seq/seq_memory.c:298
snd_seq_client_enqueue_event+0x1dd/0x2a0 sound/core/seq/seq_clientmgr.c:968
snd_seq_write+0x425/0x530 sound/core/seq/seq_clientmgr.c:1093
vfs_write+0x21a/0x7c0 fs/read_write.c:603
ksys_write+0xce/0x180 fs/read_write.c:658
__do_sys_write fs/read_write.c:670 [inline]
__se_sys_write fs/read_write.c:667 [inline]
__x64_sys_write+0x3e/0x50 fs/read_write.c:667
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880273e71b0 of 4 bytes by task 29606 on cpu 1:
snd_seq_info_pool+0xb8/0x110 sound/core/seq/seq_memory.c:500
snd_seq_info_clients_read+0x37b/0x490 sound/core/seq/seq_clientmgr.c:2473
snd_info_seq_show+0x77/0x90 sound/core/info.c:362
seq_read_iter+0x2ef/0x8e0 fs/seq_file.c:228
seq_read+0x221/0x260 fs/seq_file.c:159
pde_read fs/proc/inode.c:321 [inline]
proc_reg_read+0x119/0x1b0 fs/proc/inode.c:333
do_loop_readv_writev fs/read_write.c:761 [inline]
do_iter_read+0x3b1/0x4b0 fs/read_write.c:803
vfs_readv fs/read_write.c:921 [inline]
do_preadv+0x139/0x210 fs/read_write.c:1013
__do_sys_preadv fs/read_write.c:1063 [inline]
__se_sys_preadv fs/read_write.c:1058 [inline]
__x64_sys_preadv+0x54/0x60 fs/read_write.c:1058
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: 29606 Comm: syz-executor.5 Not tainted 5.10.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.