[alsa-devel] [PATCH] alsa-lib/tlv: fix handling of raw value ranges

[Takashi Iwai]

At Tue, 22 May 2012 18:06:34 +0200 (CEST),
Benoît Thébaudeau wrote:
> 
> Hi Takashi,
> 
> Takashi Iwai wrote:
> > It's OK to put an attachment, but I failed to apply it.
> > Please check the patch you sent can be really applied cleanly to
> > alsa-lib git tree.
> 
> My copy/paste damaged tabs. Hopefully, this should now work.

Thanks, applied now.


Takashi

> 
> Regards,
> Benoît
> [2 improve-tlv-raw-val-robustness.patch <text/x-patch (base64)>]
> alsa-lib/tlv: improve robustness of raw value ranges
> 
> snd_tlv_convert_from_dB() relies on rangemin/max blindly. Since this function is
> exported, it is better for robustness and consistency to parse the range
> properly, which this patch does.
> 
> Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau at advansee.com>
> 
> --- alsa-lib/src/control/tlv.c
> +++ alsa-lib/src/control/tlv.c
> @@ -291,41 +291,37 @@ int snd_tlv_convert_from_dB(unsigned int
>  {
>  	switch (tlv[0]) {
>  	case SND_CTL_TLVT_DB_RANGE: {
> -		long dbmin, dbmax, prev_rangemax;
> +		long dbmin, dbmax, prev_submax;
>  		unsigned int pos, len;
>  		len = int_index(tlv[1]);
> -		if (len > MAX_TLV_RANGE_SIZE)
> +		if (len < 6 || len > MAX_TLV_RANGE_SIZE)
>  			return -EINVAL;
> -		if (snd_tlv_get_dB_range(tlv, rangemin, rangemax,
> -					 &dbmin, &dbmax))
> -			return -EINVAL;
> -		if (db_gain <= dbmin) {
> -			*value = rangemin;
> -			return 0;
> -		} else if (db_gain >= dbmax) {
> -			*value = rangemax;
> -			return 0;
> -		}
>  		pos = 2;
> -		prev_rangemax = 0;
> +		prev_submax = 0;
>  		while (pos + 4 <= len) {
> -			rangemin = (int)tlv[pos];
> -			rangemax = (int)tlv[pos + 1];
> +			long submin, submax;
> +			submin = (int)tlv[pos];
> +			submax = (int)tlv[pos + 1];
> +			if (rangemax < submax)
> +				submax = rangemax;
>  			if (!snd_tlv_get_dB_range(tlv + pos + 2,
> -						  rangemin, rangemax,
> +						  submin, submax,
>  						  &dbmin, &dbmax) &&
>  			    db_gain >= dbmin && db_gain <= dbmax)
>  				return snd_tlv_convert_from_dB(tlv + pos + 2,
> -							       rangemin, rangemax,
> +							       submin, submax,
>  							       db_gain, value, xdir);
>  			else if (db_gain < dbmin) {
> -				*value = xdir ? rangemin : prev_rangemax;
> +				*value = xdir || pos == 2 ? submin : prev_submax;
>  				return 0;
>  			}
> -			prev_rangemax = rangemax;
> +			prev_submax = submax;
> +			if (rangemax == submax)
> +				break;
>  			pos += int_index(tlv[pos + 3]) + 4;
>  		}
> -		return -EINVAL;
> +		*value = prev_submax;
> +		return 0;
>  	}
>  	case SND_CTL_TLVT_DB_SCALE: {
>  		int min, step, max;