ALSA: pcm: Fix races among concurrent prealloc proc writes

stable inclusion
from linux-4.19.243
commit e14dca613e0a6ddc2bf6e360f16936a9f865205b
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I50WAS


CVE: CVE-2022-1048

--------------------------------

commit 69534c48 upstream.

We have no protection against concurrent PCM buffer preallocation
changes via proc files, and it may potentially lead to UAF or some
weird problem.  This patch applies the PCM open_mutex to the proc
write operation for avoiding the racy proc writes and the PCM stream
open (and further operations).

Cc: <stable@vger.kernel.org>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20220322170720.3529-5-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>
[OP: backport to 4.19: adjusted context]
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Rui Xiang <rui.xiang@huawei.com>
Reviewed-by: zhangxiaoxu <zhangxiaoxu5@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>