[PATCH] drm: sysfs: Use scnprintf() for avoiding potential buffer overflow

[Thomas Zimmermann]

Hi Takashi

Am 11.03.20 um 08:35 schrieb Takashi Iwai:
> Since snprintf() returns the would-be-output size instead of the
> actual output size, the succeeding calls may go beyond the given
> buffer limit.  Fix it by replacing with scnprintf().
> 
> Signed-off-by: Takashi Iwai <tiwai at suse.de>
> ---
>  drivers/gpu/drm/drm_sysfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
> index dd2bc85f43cc..9b3180e8c12f 100644
> --- a/drivers/gpu/drm/drm_sysfs.c
> +++ b/drivers/gpu/drm/drm_sysfs.c
> @@ -230,7 +230,7 @@ static ssize_t modes_show(struct device *device,
>  
>  	mutex_lock(&connector->dev->mode_config.mutex);
>  	list_for_each_entry(mode, &connector->modes, head) {
> -		written += snprintf(buf + written, PAGE_SIZE - written, "%s\n",
> +		written += scnprintf(buf + written, PAGE_SIZE - written, "%s\n",
>  				    mode->name);
>  	}
>  	mutex_unlock(&connector->dev->mode_config.mutex);
> 

In drm_sysfs.c, there are more _show functions with calls to snprintf()
that could be replaced by scnprintf(). ATM they don't return the correct
length for output that exceeds PAGE_SIZE. since you're at it, you may
replace them as well.

But in any case

Reviewed-by: Thomas Zimmermann <tzimmermann at suse.de>

for this patch.

Do you want me to merge the patch into drm-misc-next?

Best regards
Thomas


-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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