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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>
(cherry picked from commit 8000d484b8)

Conflicts:

	libavcodec/cabac.h

Conflicts:

	libavcodec/h264_cabac.c
	libavcodec/h264_slice.c
This commit is contained in:
Michael Niedermayer 2015-11-27 13:37:50 +01:00
parent e8054a9595
commit 20de3b007b
5 changed files with 15 additions and 5 deletions
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5
libavcodec/cabac.c
View File

@ -51,7 +51,7 @@ 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;
@ -64,6 +64,9 @@ 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;
}
void ff_init_cabac_states(void)

2
libavcodec/cabac.h
View File

@ -56,7 +56,7 @@ 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);
void ff_init_cabac_states(void);
#endif /* AVCODEC_CABAC_H */

3
libavcodec/cabac_functions.h
View File

@ -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
View File

@ -1999,6 +1999,7 @@ 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
@ -2015,7 +2016,9 @@ decode_intra_mb:
h->intra_pcm_ptr = ptr;
ptr += mb_size;
ff_init_cabac_decoder(&h->cabac, ptr, h->cabac.bytestream_end - ptr);
ret = ff_init_cabac_decoder(&h->cabac, ptr, h->cabac.bytestream_end - ptr);
if (ret < 0)
return ret;
// All blocks are present
h->cbp_table[mb_xy] = 0xf7ef;

5
libavcodec/h264_slice.c
View File

@ -2445,13 +2445,16 @@ static int decode_slice(struct AVCodecContext *avctx, void *arg)
}
if (h->pps.cabac) {
int ret;
/* realign */
align_get_bits(&h->gb);
/* init cabac */
ff_init_cabac_decoder(&h->cabac,
ret = ff_init_cabac_decoder(&h->cabac,
h->gb.buffer + get_bits_count(&h->gb) / 8,
(get_bits_left(&h->gb) + 7) / 8);
if (ret < 0)
return ret;
ff_h264_init_cabac_states(h);