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@xxxxxxxxxxx>
> Signed-off-by: Tuo Li <islituo@xxxxxxxxx>
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
>
