From e4fc0e51fa628395ae3101613cc099a818d9eba8 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Sun, 9 Oct 2022 09:05:42 +0000
Subject: [PATCH] ALSA: pcm: oss: Fix race at SNDCTL_DSP_SYNC
stable inclusion
from stable-v5.4.215
commit 4051324a6dafd7053c74c475e80b3ba10ae672b0
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I5T9C3
CVE: CVE-2022-3303
---------------------------
[ Upstream commit 8423f0b6d513b259fdab9c9bf4aaa6188d054c2d ]
There is a small race window at snd_pcm_oss_sync() that is called from
OSS PCM SNDCTL_DSP_SYNC ioctl; namely the function calls
snd_pcm_oss_make_ready() at first, then takes the params_lock mutex
for the rest. When the stream is set up again by another thread
between them, it leads to inconsistency, and may result in unexpected
results such as NULL dereference of OSS buffer as a fuzzer spotted
recently.
The fix is simply to cover snd_pcm_oss_make_ready() call into the same
params_lock mutex with snd_pcm_oss_make_ready_locked() variant.
Reported-and-tested-by: butt3rflyh4ck <butterflyhuangxx@gmail.com>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/CAFcO6XN7JDM4xSXGhtusQfS2mSBcx50VJKwQpCq=WeLt57aaZA@mail.gmail.com
Link: https://lore.kernel.org/r/20220905060714.22549-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Xia Longlong <xialonglong1@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>
---
sound/core/oss/pcm_oss.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index 41abb8bd466a..29c5f572ca3b 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -1653,13 +1653,14 @@ static int snd_pcm_oss_sync(struct snd_pcm_oss_file *pcm_oss_file)
runtime = substream->runtime;
if (atomic_read(&substream->mmap_count))
goto __direct;
- if ((err = snd_pcm_oss_make_ready(substream)) < 0)
- return err;
atomic_inc(&runtime->oss.rw_ref);
if (mutex_lock_interruptible(&runtime->oss.params_lock)) {
atomic_dec(&runtime->oss.rw_ref);
return -ERESTARTSYS;
}
+ err = snd_pcm_oss_make_ready_locked(substream);
+ if (err < 0)
+ goto unlock;
format = snd_pcm_oss_format_from(runtime->oss.format);
width = snd_pcm_format_physical_width(format);
if (runtime->oss.buffer_used > 0) {
--
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