2014-02-28 03:54:35

by Xiubo Li

Subject: [PATCH] ASoC: cache: Do the codec->reg_cache zero pionter check

For the snd_soc_cache_init(), the reg_size maybe zero and then the value
of codec->reg_cache, which is alloced via kzalloc, maybe equal to
ZERO_SIZE_PTR. If the reg parameter of snd_soc_cache_write() is large enough,
the cache[idx] = val maybe cause the kernel crash...

So this patch fix this via doing the zero pionter check of it.

Signed-off-by: Xiubo Li <[email protected]>
---
sound/soc/soc-cache.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/sound/soc/soc-cache.c b/sound/soc/soc-cache.c
index 375dc6d..bfed3e4 100644
--- a/sound/soc/soc-cache.c
+++ b/sound/soc/soc-cache.c
@@ -96,8 +96,7 @@ int snd_soc_cache_exit(struct snd_soc_codec *codec)
{
dev_dbg(codec->dev, "ASoC: Destroying cache for %s codec\n",
codec->name);
- if (!codec->reg_cache)
- return 0;
+
kfree(codec->reg_cache);
codec->reg_cache = NULL;
return 0;
@@ -117,8 +116,9 @@ int snd_soc_cache_read(struct snd_soc_codec *codec,
return -EINVAL;

mutex_lock(&codec->cache_rw_mutex);
- *value = snd_soc_get_cache_val(codec->reg_cache, reg,
- codec->driver->reg_word_size);
+ if (!ZERO_OR_NULL_PTR(codec->reg_cache))
+ *value = snd_soc_get_cache_val(codec->reg_cache, reg,
+ codec->driver->reg_word_size);
mutex_unlock(&codec->cache_rw_mutex);

return 0;
@@ -136,8 +136,9 @@ int snd_soc_cache_write(struct snd_soc_codec *codec,
unsigned int reg, unsigned int value)
{
mutex_lock(&codec->cache_rw_mutex);
- snd_soc_set_cache_val(codec->reg_cache, reg, value,
- codec->driver->reg_word_size);
+ if (!ZERO_OR_NULL_PTR(codec->reg_cache))
+ snd_soc_set_cache_val(codec->reg_cache, reg, value,
+ codec->driver->reg_word_size);
mutex_unlock(&codec->cache_rw_mutex);

return 0;
--
1.8.4

2014-02-28 06:58:12

by Lars-Peter Clausen

Subject: Re: [alsa-devel] [PATCH] ASoC: cache: Do the codec->reg_cache zero pionter check

On 02/28/2014 03:48 AM, Xiubo Li wrote:
> For the snd_soc_cache_init(), the reg_size maybe zero and then the value
> of codec->reg_cache, which is alloced via kzalloc, maybe equal to
> ZERO_SIZE_PTR. If the reg parameter of snd_soc_cache_write() is large enough,
> the cache[idx] = val maybe cause the kernel crash...
>

There are actually no users of snd_soc_cache_{read,write}() left. Since all
drivers using snd_soc_set_cache_io() are now using native regmap the path in
hw_{read,write} that does call snd_soc_cache_{read,write}() is never hit.

If you want to avoid this theoretical issue just remove the functions.

> So this patch fix this via doing the zero pionter check of it.
>
> Signed-off-by: Xiubo Li <[email protected]>
> ---
> sound/soc/soc-cache.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/sound/soc/soc-cache.c b/sound/soc/soc-cache.c
> index 375dc6d..bfed3e4 100644
> --- a/sound/soc/soc-cache.c
> +++ b/sound/soc/soc-cache.c
> @@ -96,8 +96,7 @@ int snd_soc_cache_exit(struct snd_soc_codec *codec)
> {
> dev_dbg(codec->dev, "ASoC: Destroying cache for %s codec\n",
> codec->name);
> - if (!codec->reg_cache)
> - return 0;
> +
> kfree(codec->reg_cache);
> codec->reg_cache = NULL;
> return 0;
> @@ -117,8 +116,9 @@ int snd_soc_cache_read(struct snd_soc_codec *codec,
> return -EINVAL;
>
> mutex_lock(&codec->cache_rw_mutex);
> - *value = snd_soc_get_cache_val(codec->reg_cache, reg,
> - codec->driver->reg_word_size);
> + if (!ZERO_OR_NULL_PTR(codec->reg_cache))
> + *value = snd_soc_get_cache_val(codec->reg_cache, reg,
> + codec->driver->reg_word_size);
> mutex_unlock(&codec->cache_rw_mutex);
>
> return 0;
> @@ -136,8 +136,9 @@ int snd_soc_cache_write(struct snd_soc_codec *codec,
> unsigned int reg, unsigned int value)
> {
> mutex_lock(&codec->cache_rw_mutex);
> - snd_soc_set_cache_val(codec->reg_cache, reg, value,
> - codec->driver->reg_word_size);
> + if (!ZERO_OR_NULL_PTR(codec->reg_cache))
> + snd_soc_set_cache_val(codec->reg_cache, reg, value,
> + codec->driver->reg_word_size);
> mutex_unlock(&codec->cache_rw_mutex);
>
> return 0;
>