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ac3: detect dba errors and prevent writing past end of array 

Originally committed as revision 16034 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2008-12-08 03:13:20 +00:00
parent b9f382c8ef
commit 72a6244b5d
3 changed files with 15 additions and 6 deletions
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11
libavcodec/ac3.c
View File

@ -80,7 +80,7 @@ void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
} while (end > band_start_tab[k]);
}
void ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
int start, int end, int fast_gain, int is_lfe,
int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
uint8_t *dba_lengths, uint8_t *dba_values,
@ -156,9 +156,13 @@ void ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
if (dba_mode == DBA_REUSE || dba_mode == DBA_NEW) {
int band, seg, delta;
if (dba_nsegs >= 8)
return -1;
band = 0;
for (seg = 0; seg < FFMIN(8, dba_nsegs); seg++) {
band = FFMIN(49, band + dba_offsets[seg]);
for (seg = 0; seg < dba_nsegs; seg++) {
band += dba_offsets[seg];
if (band >= 50 || dba_lengths[seg] > 50-band)
return -1;
if (dba_values[seg] >= 4) {
delta = (dba_values[seg] - 3) << 7;
} else {
@ -170,6 +174,7 @@ void ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
}
}
}
return 0;
}
void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end,

3
libavcodec/ac3.h
View File

@ -149,8 +149,9 @@ void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
* @param[in] dba_lengths length of each segment
* @param[in] dba_values delta bit allocation for each segment
* @param[out] mask calculated masking curve
* @return returns 0 for success, non-zero for error
*/
void ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
int start, int end, int fast_gain, int is_lfe,
int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
uint8_t *dba_lengths, uint8_t *dba_values,

7
libavcodec/ac3dec.c
View File

@ -1133,12 +1133,15 @@ static int decode_audio_block(AC3DecodeContext *s, int blk)
if(bit_alloc_stages[ch] > 1) {
/* Compute excitation function, Compute masking curve, and
Apply delta bit allocation */
ff_ac3_bit_alloc_calc_mask(&s->bit_alloc_params, s->band_psd[ch],
if (ff_ac3_bit_alloc_calc_mask(&s->bit_alloc_params, s->band_psd[ch],
s->start_freq[ch], s->end_freq[ch],
s->fast_gain[ch], (ch == s->lfe_ch),
s->dba_mode[ch], s->dba_nsegs[ch],
s->dba_offsets[ch], s->dba_lengths[ch],
s->dba_values[ch], s->mask[ch]);
s->dba_values[ch], s->mask[ch])) {
av_log(s->avctx, AV_LOG_ERROR, "error in bit allocation\n");
return -1;
}
}
if(bit_alloc_stages[ch] > 0) {
/* Compute bit allocation */