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avcodec/cabac: Check initial cabac decoder state 

Fixes integer overflows
Fixes: 1430e9c43fae47a24c179c7c54f94918/signal_sigsegv_421427_2340_591e9810c7b09efe501ad84638c9e9f8.264

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Found-by: xiedingbao (Ticket4727)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2015-11-27 13:37:50 +01:00
parent a1f6b05f52
commit 8000d484b8
5 changed files with 14 additions and 5 deletions
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5
libavcodec/cabac.c
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@ -175,7 +175,7 @@ void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size){
*
* @param buf_size size of buf in bits
*/
void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size){
int ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size){
c->bytestream_start=
c->bytestream= buf;
c->bytestream_end= buf + buf_size;
@ -188,6 +188,9 @@ void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size){
#endif
c->low+= ((*c->bytestream++)<<2) + 2;
c->range= 0x1FE;
if ((c->range<<(CABAC_BITS+1)) < c->low)
return AVERROR_INVALIDDATA;
return 0;
}
#ifdef TEST

2
libavcodec/cabac.h
View File

@ -51,6 +51,6 @@ typedef struct CABACContext{
}CABACContext;
void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size);
void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size);
int ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size);
#endif /* AVCODEC_CABAC_H */

3
libavcodec/cabac_functions.h
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@ -191,7 +191,8 @@ static av_unused const uint8_t* skip_bytes(CABACContext *c, int n) {
#endif
if ((int) (c->bytestream_end - ptr) < n)
return NULL;
ff_init_cabac_decoder(c, ptr + n, c->bytestream_end - ptr - n);
if (ff_init_cabac_decoder(c, ptr + n, c->bytestream_end - ptr - n) < 0)
return NULL;
return ptr;
}

5
libavcodec/h264_cabac.c
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@ -2026,6 +2026,7 @@ decode_intra_mb:
const int mb_size = ff_h264_mb_sizes[h->sps.chroma_format_idc] *
h->sps.bit_depth_luma >> 3;
const uint8_t *ptr;
int ret;
// We assume these blocks are very rare so we do not optimize it.
// FIXME The two following lines get the bitstream position in the cabac
@ -2042,7 +2043,9 @@ decode_intra_mb:
sl->intra_pcm_ptr = ptr;
ptr += mb_size;
ff_init_cabac_decoder(&sl->cabac, ptr, sl->cabac.bytestream_end - ptr);
ret = ff_init_cabac_decoder(&sl->cabac, ptr, sl->cabac.bytestream_end - ptr);
if (ret < 0)
return ret;
// All blocks are present
h->cbp_table[mb_xy] = 0xf7ef;

4
libavcodec/h264_slice.c
View File

@ -2372,9 +2372,11 @@ static int decode_slice(struct AVCodecContext *avctx, void *arg)
align_get_bits(&sl->gb);
/* init cabac */
ff_init_cabac_decoder(&sl->cabac,
ret = ff_init_cabac_decoder(&sl->cabac,
sl->gb.buffer + get_bits_count(&sl->gb) / 8,
(get_bits_left(&sl->gb) + 7) / 8);
if (ret < 0)
return ret;
ff_h264_init_cabac_states(h, sl);