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alsdec: fix number of decoded samples in first sub-block in BGMC mode.

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Fixes CVE-2012-2790

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: Justin Ruggles <justin.ruggles@gmail.com>
This commit is contained in:
Thilo Borgmann 2012-04-15 18:07:12 +02:00 committed by Justin Ruggles
parent 97f0efbfb8
commit 66197988b1
1 changed files with 6 additions and 6 deletions
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12
libavcodec/alsdec.c
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@ -770,7 +770,6 @@ static int read_var_block_data(ALSDecContext *ctx, ALSBlockData *bd)
int delta[8];
unsigned int k [8];
unsigned int b = av_clip((av_ceil_log2(bd->block_length) - 3) >> 1, 0, 5);
unsigned int i;
// read most significant bits
unsigned int high;
@ -782,28 +781,29 @@ static int read_var_block_data(ALSDecContext *ctx, ALSBlockData *bd)
current_res = bd->raw_samples + start;
for (sb = 0; sb < sub_blocks; sb++) {
unsigned int sb_len = sb_length - (sb ? 0 : start);
k [sb] = s[sb] > b ? s[sb] - b : 0;
delta[sb] = 5 - s[sb] + k[sb];
ff_bgmc_decode(gb, sb_length, current_res,
ff_bgmc_decode(gb, sb_len, current_res,
delta[sb], sx[sb], &high, &low, &value, ctx->bgmc_lut, ctx->bgmc_lut_status);
current_res += sb_length;
current_res += sb_len;
}
ff_bgmc_decode_end(gb);
// read least significant bits and tails
i = start;
current_res = bd->raw_samples + start;
for (sb = 0; sb < sub_blocks; sb++, i = 0) {
for (sb = 0; sb < sub_blocks; sb++, start = 0) {
unsigned int cur_tail_code = tail_code[sx[sb]][delta[sb]];
unsigned int cur_k = k[sb];
unsigned int cur_s = s[sb];
for (; i < sb_length; i++) {
for (; start < sb_length; start++) {
int32_t res = *current_res;
if (res == cur_tail_code) {