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qdm2: clip array indices returned by qdm2_get_vlc().

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Prevents subsequent overreads when these numbers are used as indices
in arrays.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org

Signed-off-by: Justin Ruggles <justin.ruggles@gmail.com>
pull/30/merge
Ronald S. Bultje 13 years ago committed by Justin Ruggles
parent 85e5b866dc
commit 64953f67f9
1 changed files with 13 additions and 5 deletions
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  1. 18
      libavcodec/qdm2.c

18
libavcodec/qdm2.c
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@ -879,9 +879,13 @@ static void synthfilt_build_sb_samples (QDM2Context *q, GetBitContext *gb, int l
break;
case 30:
if (get_bits_left(gb) >= 4)
samples[0] = type30_dequant[qdm2_get_vlc(gb, &vlc_tab_type30, 0, 1)];
else
if (get_bits_left(gb) >= 4) {
unsigned index = qdm2_get_vlc(gb, &vlc_tab_type30, 0, 1);
if (index < FF_ARRAY_ELEMS(type30_dequant)) {
samples[0] = type30_dequant[index];
} else
samples[0] = SB_DITHERING_NOISE(sb,q->noise_idx);
} else
samples[0] = SB_DITHERING_NOISE(sb,q->noise_idx);
run = 1;
@ -895,8 +899,12 @@ static void synthfilt_build_sb_samples (QDM2Context *q, GetBitContext *gb, int l
type34_predictor = samples[0];
type34_first = 0;
} else {
samples[0] = type34_delta[qdm2_get_vlc(gb, &vlc_tab_type34, 0, 1)] / type34_div + type34_predictor;
type34_predictor = samples[0];
unsigned index = qdm2_get_vlc(gb, &vlc_tab_type34, 0, 1);
if (index < FF_ARRAY_ELEMS(type34_delta)) {
samples[0] = type34_delta[index] / type34_div + type34_predictor;
type34_predictor = samples[0];
} else
samples[0] = SB_DITHERING_NOISE(sb,q->noise_idx);
}
} else {
samples[0] = SB_DITHERING_NOISE(sb,q->noise_idx);

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