On Mon, 03 Jul 2023 05:10:16 +0200, Tuo Li wrote:
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().
Reported-by: BassCheck bass@buaa.edu.cn Signed-off-by: Tuo Li islituo@gmail.com
Practically seen, it's pretty harmless, as the flag is set at the very beginning of the codec driver probe, while snd_hdac_regmap_sync() is used only in the runtime PM resume that must not happen during the probe. IOW, codec->regmap_lock itself isn't really meant to protectthe change of codec->regmap flag.
OTOH, your change makes things more consistent, so I applied the patch now.
Thanks!
Takashi
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 fe3587547cfe..39610a15bcc9 100644 --- a/sound/hda/hdac_regmap.c +++ b/sound/hda/hdac_regmap.c @@ -597,10 +597,9 @@ 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); -- 2.34.1