Re: [PATCH v2 1/1] drm: modes: fix DRM modes analysis regression

[Jani Nikula]

On Wed, 09 Dec 2015, LABBE Corentin <clabbe.montjoie@xxxxxxxxx> wrote:
> My latest commit introduce some case where a valid mode, could be
> rejected.
> simple_strtox functions stop at first non-digit character, but kstrtox not.
> So args like "video=HDMI-A-1:720x480-16@60" will be reject when checking 16@.
> The proper solution is to store digits in a specific buffer.

Or to revert regressing commit...? Your original commit complicated the
already complicated function, and this one makes it more so. What is the
benefit?

> Fixes: 52157a4ca396 ("drm: modes: replace simple_strtoul by kstrtouint")

For me the commit id is cc344980c76748e57c9c03100c2a14d36ab00334.

BR,
Jani.

> Reported-by: Kuninori Morimoto <kuninori.morimoto.gx@xxxxxxxxxxx>
> Signed-off-by: LABBE Corentin <clabbe.montjoie@xxxxxxxxx>
> ---
>  drivers/gpu/drm/drm_modes.c | 28 +++++++++++++++++++++-------
>  1 file changed, 21 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
> index bde9b29..da1e80d 100644
> --- a/drivers/gpu/drm/drm_modes.c
> +++ b/drivers/gpu/drm/drm_modes.c
> @@ -1225,13 +1225,14 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
>  					       struct drm_cmdline_mode *mode)
>  {
>  	const char *name;
> -	unsigned int namelen;
> +	unsigned int namelen, digit_i;
>  	bool res_specified = false, bpp_specified = false, refresh_specified = false;
>  	unsigned int xres = 0, yres = 0, bpp = 32, refresh = 0;
>  	bool yres_specified = false, cvt = false, rb = false;
>  	bool interlace = false, margins = false, was_digit = false;
>  	int i, err;
>  	enum drm_connector_force force = DRM_FORCE_UNSPECIFIED;
> +	char *digits;
>  
>  #ifdef CONFIG_FB
>  	if (!mode_option)
> @@ -1245,42 +1246,53 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
>  
>  	name = mode_option;
>  	namelen = strlen(name);
> +
> +	digits = kzalloc(namelen, GFP_KERNEL);
> +	if (!digits)
> +		return false;
> +	/* The last character must be the last 0 */
> +	digit_i = namelen;
> +
>  	for (i = namelen-1; i >= 0; i--) {
>  		switch (name[i]) {
>  		case '@':
>  			if (!refresh_specified && !bpp_specified &&
>  			    !yres_specified && !cvt && !rb && was_digit) {
> -				err = kstrtouint(&name[i + 1], 10, &refresh);
> +				err = kstrtouint(&digits[digit_i], 10, &refresh);
>  				if (err)
> -					return false;
> +					goto done;
>  				refresh_specified = true;
>  				was_digit = false;
> +				digit_i = namelen;
>  			} else
>  				goto done;
>  			break;
>  		case '-':
>  			if (!bpp_specified && !yres_specified && !cvt &&
>  			    !rb && was_digit) {
> -				err = kstrtouint(&name[i + 1], 10, &bpp);
> +				err = kstrtouint(&digits[digit_i], 10, &bpp);
>  				if (err)
> -					return false;
> +					goto done;
>  				bpp_specified = true;
>  				was_digit = false;
> +				digit_i = namelen;
>  			} else
>  				goto done;
>  			break;
>  		case 'x':
>  			if (!yres_specified && was_digit) {
> -				err = kstrtouint(&name[i + 1], 10, &yres);
> +				err = kstrtouint(&digits[digit_i], 10, &yres);
>  				if (err)
> -					return false;
> +					goto done;
>  				yres_specified = true;
>  				was_digit = false;
> +				digit_i = namelen;
>  			} else
>  				goto done;
>  			break;
>  		case '0' ... '9':
>  			was_digit = true;
> +			digits[--digit_i] = name[i];
>  			break;
>  		case 'M':
>  			if (yres_specified || cvt || was_digit)
> @@ -1349,6 +1361,7 @@ done:
>  			"parse error at position %i in video mode '%s'\n",
>  			i, name);
>  		mode->specified = false;
> +		kfree(digits);
>  		return false;
>  	}
>  
> @@ -1373,6 +1386,7 @@ done:
>  	mode->margins = margins;
>  	mode->force = force;
>  
> +	kfree(digits);
>  	return true;
>  }
>  EXPORT_SYMBOL(drm_mode_parse_command_line_for_connector);

-- 
Jani Nikula, Intel Open Source Technology Center
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