2021-12-14 15:25:39

by Miaoqian Lin

Subject: [PATCH] ASoC: wcd934x: Fix a incorrect use of kstrndup

In wcd934x_codec_enable_dec(), widget_name is allocated by kstrndup().
However, according to doc: "Note: Use kmemdup_nul() instead if the size
is known exactly." So we should use kmemdup_nul() here instead of
kstrndup(). It's similar to CVE-2019-12454.

Signed-off-by: Miaoqian Lin <[email protected]>
---
sound/soc/codecs/wcd934x.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/soc/codecs/wcd934x.c b/sound/soc/codecs/wcd934x.c
index e63c6b723d76..c6677cfbce59 100644
--- a/sound/soc/codecs/wcd934x.c
+++ b/sound/soc/codecs/wcd934x.c
@@ -5005,7 +5005,7 @@ static int wcd934x_codec_enable_dec(struct snd_soc_dapm_widget *w,
char *dec;
u8 hpf_coff_freq;

- widget_name = kstrndup(w->name, 15, GFP_KERNEL);
+ widget_name = kmemdup_nul(w->name, 15, GFP_KERNEL);
if (!widget_name)
return -ENOMEM;

--
2.17.1

2021-12-14 17:35:53

by Lars-Peter Clausen

Subject: Re: [PATCH] ASoC: wcd934x: Fix a incorrect use of kstrndup

On 12/14/21 4:25 PM, Miaoqian Lin wrote:
> In wcd934x_codec_enable_dec(), widget_name is allocated by kstrndup().
> However, according to doc: "Note: Use kmemdup_nul() instead if the size
> is known exactly." So we should use kmemdup_nul() here instead of
> kstrndup(). It's similar to CVE-2019-12454.
>
> Signed-off-by: Miaoqian Lin <[email protected]>
> ---
> sound/soc/codecs/wcd934x.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sound/soc/codecs/wcd934x.c b/sound/soc/codecs/wcd934x.c
> index e63c6b723d76..c6677cfbce59 100644
> --- a/sound/soc/codecs/wcd934x.c
> +++ b/sound/soc/codecs/wcd934x.c
> @@ -5005,7 +5005,7 @@ static int wcd934x_codec_enable_dec(struct snd_soc_dapm_widget *w,
> char *dec;
> u8 hpf_coff_freq;
>
> - widget_name = kstrndup(w->name, 15, GFP_KERNEL);
> + widget_name = kmemdup_nul(w->name, 15, GFP_KERNEL);
I'm wondering if it isn't better to re-structure the code to not
allocate any memory.

something like

ret = sscan(w->name, "ADC MUX%d", &decimator);
if (ret != 1)
    ...

2021-12-14 17:42:50

by Lars-Peter Clausen

Subject: Re: [PATCH] ASoC: wcd934x: Fix a incorrect use of kstrndup

On 12/14/21 4:25 PM, Miaoqian Lin wrote:
> In wcd934x_codec_enable_dec(), widget_name is allocated by kstrndup().
> However, according to doc: "Note: Use kmemdup_nul() instead if the size
> is known exactly." So we should use kmemdup_nul() here instead of
> kstrndup(). It's similar to CVE-2019-12454.
>
> Signed-off-by: Miaoqian Lin <[email protected]>
> ---
> sound/soc/codecs/wcd934x.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sound/soc/codecs/wcd934x.c b/sound/soc/codecs/wcd934x.c
> index e63c6b723d76..c6677cfbce59 100644
> --- a/sound/soc/codecs/wcd934x.c
> +++ b/sound/soc/codecs/wcd934x.c
> @@ -5005,7 +5005,7 @@ static int wcd934x_codec_enable_dec(struct snd_soc_dapm_widget *w,
> char *dec;
> u8 hpf_coff_freq;
>
> - widget_name = kstrndup(w->name, 15, GFP_KERNEL);
> + widget_name = kmemdup_nul(w->name, 15, GFP_KERNEL);

Thinking a bit more about it, this is wrong. The source string is
shorter than 15 character. So with this change you are copying past the
end of the string, which depending on where in memory the string is
placed can cause undefined behavior.