[PATCH linux-next] ALSA: control-led: use strscpy() to instead of strncpy()

[PATCH linux-next] ALSA: control-led: use strscpy() to instead of strncpy()

[yang.yang29]

From: Xu Panda <xu.panda@zte.com.cn>

The implementation of strscpy() is more robust and safer.
That's now the recommended way to copy NUL-terminated strings.

Signed-off-by: Xu Panda <xu.panda@zte.com.cn>
Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
---
 sound/core/control_led.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/sound/core/control_led.c b/sound/core/control_led.c
index f975cc85772b..c88653c205eb 100644
--- a/sound/core/control_led.c
+++ b/sound/core/control_led.c
@@ -534,8 +534,7 @@ static ssize_t set_led_id(struct snd_ctl_led_card *led_card, const char *buf, si
 	struct snd_ctl_elem_id id;
 	int err;

-	strncpy(buf2, buf, len);
-	buf2[len] = '\0';
+	strncpy(buf2, buf, len + 1);
 	memset(&id, 0, sizeof(id));
 	id.iface = SNDRV_CTL_ELEM_IFACE_MIXER;
 	s = buf2;
-- 
2.15.2

Re: [PATCH linux-next] ALSA: control-led: use strscpy() to instead of strncpy()

[Takashi Iwai]

On Mon, 09 Jan 2023 12:45:51 +0100,
<yang.yang29@zte.com.cn> wrote:
> 
> From: Xu Panda <xu.panda@zte.com.cn>
> 
> The implementation of strscpy() is more robust and safer.
> That's now the recommended way to copy NUL-terminated strings.
> 
> Signed-off-by: Xu Panda <xu.panda@zte.com.cn>
> Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
> ---
>  sound/core/control_led.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/sound/core/control_led.c b/sound/core/control_led.c
> index f975cc85772b..c88653c205eb 100644
> --- a/sound/core/control_led.c
> +++ b/sound/core/control_led.c
> @@ -534,8 +534,7 @@ static ssize_t set_led_id(struct snd_ctl_led_card *led_card, const char *buf, si
>  	struct snd_ctl_elem_id id;
>  	int err;
> 
> -	strncpy(buf2, buf, len);
> -	buf2[len] = '\0';
> +	strncpy(buf2, buf, len + 1);

Still using strncpy()...?


thanks,

Takashi

Re: [PATCH linux-next] ALSA: control-led: use strscpy() to instead of strncpy()

[Jaroslav Kysela]

On 09. 01. 23 13:40, Takashi Iwai wrote:
> On Mon, 09 Jan 2023 12:45:51 +0100,
> <yang.yang29@zte.com.cn> wrote:
>>
>> From: Xu Panda <xu.panda@zte.com.cn>
>>
>> The implementation of strscpy() is more robust and safer.
>> That's now the recommended way to copy NUL-terminated strings.
>>
>> Signed-off-by: Xu Panda <xu.panda@zte.com.cn>
>> Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
>> ---
>>   sound/core/control_led.c | 3 +--
>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/sound/core/control_led.c b/sound/core/control_led.c
>> index f975cc85772b..c88653c205eb 100644
>> --- a/sound/core/control_led.c
>> +++ b/sound/core/control_led.c
>> @@ -534,8 +534,7 @@ static ssize_t set_led_id(struct snd_ctl_led_card *led_card, const char *buf, si
>>   	struct snd_ctl_elem_id id;
>>   	int err;
>>
>> -	strncpy(buf2, buf, len);
>> -	buf2[len] = '\0';
>> +	strncpy(buf2, buf, len + 1);
> 
> Still using strncpy()...?

The original code should be:

diff --git a/sound/core/control_led.c b/sound/core/control_led.c
index f975cc85772b..b44abefcb593 100644
--- a/sound/core/control_led.c
+++ b/sound/core/control_led.c
@@ -530,7 +530,7 @@ static ssize_t set_led_id(struct snd_ctl_led_card 
*led_card, const char *buf, si
                           bool attach)
  {
         char buf2[256], *s, *os;
-       size_t len = max(sizeof(s) - 1, count);
+       size_t len = min(sizeof(buf2) - 1, count);
         struct snd_ctl_elem_id id;
         int err;

But it can be replaced with:

diff --git a/sound/core/control_led.c b/sound/core/control_led.c
index f975cc85772b..41d4e898d34c 100644
--- a/sound/core/control_led.c
+++ b/sound/core/control_led.c
@@ -530,12 +530,11 @@ static ssize_t set_led_id(struct snd_ctl_led_card 
*led_card, const char *buf, si
                           bool attach)
  {
         char buf2[256], *s, *os;
-       size_t len = max(sizeof(s) - 1, count);
         struct snd_ctl_elem_id id;
         int err;

-       strncpy(buf2, buf, len);
-       buf2[len] = '\0';
+       if (strscpy(buf2, buf, count) < 0)
+               return -E2BIG;
         memset(&id, 0, sizeof(id));
         id.iface = SNDRV_CTL_ELEM_IFACE_MIXER;
         s = buf2;

I'll send a patch ASAP.

				Jaroslav

--
Jaroslav Kysela <perex@perex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.