KCSAN: data-race in snd_seq_cell_alloc / snd_seq_info

Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in snd_seq_cell_alloc / snd_seq_info_pool (2) sound				2	1252d	1229d	0/26	auto-closed as invalid on 2020/12/21 11:53

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BUG: KCSAN: data-race in snd_seq_cell_alloc / snd_seq_info_pool

write to 0xffff88811e35b530 of 4 bytes by task 26693 on cpu 0:
 snd_seq_cell_alloc+0x2ff/0x360 sound/core/seq/seq_memory.c:260
 snd_seq_event_dup+0xe5/0x410 sound/core/seq/seq_memory.c:298
 snd_seq_client_enqueue_event+0x1dd/0x2a0 sound/core/seq/seq_clientmgr.c:968
 snd_seq_write+0x435/0x550 sound/core/seq/seq_clientmgr.c:1093
 __vfs_write+0x69/0x340 fs/read_write.c:495
 vfs_write+0x19b/0x350 fs/read_write.c:559
 ksys_write+0xce/0x180 fs/read_write.c:612
 __do_sys_write fs/read_write.c:624 [inline]
 __se_sys_write fs/read_write.c:621 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:621
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88811e35b530 of 4 bytes by task 26682 on cpu 1:
 snd_seq_info_pool+0xb8/0x110 sound/core/seq/seq_memory.c:500
 snd_seq_info_clients_read+0x376/0x490 sound/core/seq/seq_clientmgr.c:2473
 snd_info_seq_show+0x77/0x90 sound/core/info.c:362
 seq_read+0x2ee/0x900 fs/seq_file.c:208
 pde_read fs/proc/inode.c:306 [inline]
 proc_reg_read+0x116/0x1a0 fs/proc/inode.c:318
 do_loop_readv_writev fs/read_write.c:715 [inline]
 do_iter_read+0x3f5/0x480 fs/read_write.c:936
 vfs_readv fs/read_write.c:1054 [inline]
 do_preadv+0x13b/0x230 fs/read_write.c:1146
 __do_sys_preadv fs/read_write.c:1196 [inline]
 __se_sys_preadv fs/read_write.c:1191 [inline]
 __x64_sys_preadv+0x54/0x60 fs/read_write.c:1191
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 26682 Comm: syz-executor.5 Not tainted 5.8.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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