linux-kernel - [PATCH stable-5.4.y 2/2] ALSA: mixer: fix deadlock in snd_mixer_oss_set

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Message-Id: <20211113153846.10996-2-tiwai@suse.de>
Date:   Sat, 13 Nov 2021 16:38:46 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH stable-5.4.y 2/2] ALSA: mixer: fix deadlock in snd_mixer_oss_set_volume

From: Pavel Skripkin <paskripkin@...il.com>

commit 3ab7992018455ac63c33e9b3eaa7264e293e40f4 upstream.

In commit 411cef6adfb3 ("ALSA: mixer: oss: Fix racy access to slots")
added mutex protection in snd_mixer_oss_set_volume(). Second
mutex_lock() in same function looks like typo, fix it.

Reported-by: syzbot+ace149a75a9a0a399ac7@...kaller.appspotmail.com
Fixes: 411cef6adfb3 ("ALSA: mixer: oss: Fix racy access to slots")
Cc: <stable@...r.kernel.org>
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
Link: https://lore.kernel.org/r/20211024140315.16704-1-paskripkin@gmail.com
Signed-off-by: Takashi Iwai <tiwai@...e.de>
---

Please apply to older stable kernels, too.

 sound/core/oss/mixer_oss.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/core/oss/mixer_oss.c b/sound/core/oss/mixer_oss.c
index fd567611f67e..50ec8b8ff68c 100644
--- a/sound/core/oss/mixer_oss.c
+++ b/sound/core/oss/mixer_oss.c
@@ -313,7 +313,7 @@ static int snd_mixer_oss_set_volume(struct snd_mixer_oss_file *fmixer,
 	pslot->volume[1] = right;
 	result = (left & 0xff) | ((right & 0xff) << 8);
  unlock:
-	mutex_lock(&mixer->reg_mutex);
+	mutex_unlock(&mixer->reg_mutex);
 	return result;
 }
 
-- 
2.26.2