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Message-Id: <20230724013426.2333833-12-sashal@kernel.org>
Date: Sun, 23 Jul 2023 21:34:25 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Tuo Li <islituo@...il.com>, BassCheck <bass@...a.edu.cn>,
Takashi Iwai <tiwai@...e.de>, Sasha Levin <sashal@...nel.org>,
perex@...ex.cz, tiwai@...e.com, alsa-devel@...a-project.org
Subject: [PATCH AUTOSEL 5.4 12/12] ALSA: hda: fix a possible null-pointer dereference due to data race in snd_hdac_regmap_sync()
From: Tuo Li <islituo@...il.com>
[ Upstream commit 1f4a08fed450db87fbb5ff5105354158bdbe1a22 ]
The variable codec->regmap is often protected by the lock
codec->regmap_lock when is accessed. However, it is accessed without
holding the lock when is accessed in snd_hdac_regmap_sync():
if (codec->regmap)
In my opinion, this may be a harmful race, because if codec->regmap is
set to NULL right after the condition is checked, a null-pointer
dereference can occur in the called function regcache_sync():
map->lock(map->lock_arg); --> Line 360 in drivers/base/regmap/regcache.c
To fix this possible null-pointer dereference caused by data race, the
mutex_lock coverage is extended to protect the if statement as well as the
function call to regcache_sync().
[ Note: the lack of the regmap_lock itself is harmless for the current
codec driver implementations, as snd_hdac_regmap_sync() is only for
PM runtime resume that is prohibited during the codec probe.
But the change makes the whole code more consistent, so it's merged
as is -- tiwai ]
Reported-by: BassCheck <bass@...a.edu.cn>
Signed-off-by: Tuo Li <islituo@...il.com>
Link: https://lore.kernel.org/r/20230703031016.1184711-1-islituo@gmail.com
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
sound/hda/hdac_regmap.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/sound/hda/hdac_regmap.c b/sound/hda/hdac_regmap.c
index 49780399c2849..a035a7d74ce09 100644
--- a/sound/hda/hdac_regmap.c
+++ b/sound/hda/hdac_regmap.c
@@ -596,10 +596,9 @@ EXPORT_SYMBOL_GPL(snd_hdac_regmap_update_raw_once);
*/
void snd_hdac_regmap_sync(struct hdac_device *codec)
{
- if (codec->regmap) {
- mutex_lock(&codec->regmap_lock);
+ mutex_lock(&codec->regmap_lock);
+ if (codec->regmap)
regcache_sync(codec->regmap);
- mutex_unlock(&codec->regmap_lock);
- }
+ mutex_unlock(&codec->regmap_lock);
}
EXPORT_SYMBOL_GPL(snd_hdac_regmap_sync);
--
2.39.2
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