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@xxxxxxxxxx> wrote:
> > From: Xu Panda <xu.panda@xxxxxxxxxx>
> >
> > 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@xxxxxxxxxx>
> > Signed-off-by: Yang Yang <yang.yang29@xxxxxxxxxx>
> > ---
> >   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@xxxxxxxx>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.