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h264: disallow constrained intra prediction modes for luma.

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Conversion of the luma intra prediction mode to one of the constrained
("alzheimer") ones can happen by crafting special bitstreams, causing
a crash because we'll call a NULL function pointer for 16x16 block intra
prediction, since constrained intra prediction functions are only
implemented for chroma (8x8 blocks).

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org
(cherry picked from commit 45b7bd7c53b41bc5ff6fc2158831f2b1b1256113)

Signed-off-by: Reinhard Tartler <siretart@tauware.de>
(cherry picked from commit 248d4e461578ff327a2fd75fd0db4f38c270918a)

Signed-off-by: Reinhard Tartler <siretart@tauware.de>
This commit is contained in:
Ronald S. Bultje 2012-02-09 22:57:01 -08:00 committed by Reinhard Tartler
parent 6362264e2d
commit 047c6ad752
5 changed files with 9 additions and 9 deletions
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4
libavcodec/h264.c
View File

@ -111,7 +111,7 @@ int ff_h264_check_intra4x4_pred_mode(H264Context *h){
/**
* checks if the top & left blocks are available if needed & changes the dc mode so it only uses the available blocks.
*/
int ff_h264_check_intra_pred_mode(H264Context *h, int mode){
int ff_h264_check_intra_pred_mode(H264Context *h, int mode, int is_chroma){
MpegEncContext * const s = &h->s;
static const int8_t top [7]= {LEFT_DC_PRED8x8, 1,-1,-1};
static const int8_t left[7]= { TOP_DC_PRED8x8,-1, 2,-1,DC_128_PRED8x8};
@ -131,7 +131,7 @@ int ff_h264_check_intra_pred_mode(H264Context *h, int mode){
if((h->left_samples_available&0x8080) != 0x8080){
mode= left[ mode ];
if(h->left_samples_available&0x8080){ //mad cow disease mode, aka MBAFF + constrained_intra_pred
if(is_chroma && (h->left_samples_available&0x8080)){ //mad cow disease mode, aka MBAFF + constrained_intra_pred
mode= ALZHEIMER_DC_L0T_PRED8x8 + (!(h->left_samples_available&0x8000)) + 2*(mode == DC_128_PRED8x8);
}
if(mode<0){

2
libavcodec/h264.h
View File

@ -656,7 +656,7 @@ int ff_h264_check_intra4x4_pred_mode(H264Context *h);
/**
* Check if the top & left blocks are available if needed & change the dc mode so it only uses the available blocks.
*/
int ff_h264_check_intra_pred_mode(H264Context *h, int mode);
int ff_h264_check_intra_pred_mode(H264Context *h, int mode, int is_chroma);
void ff_h264_write_back_intra_pred_mode(H264Context *h);
void ff_h264_hl_decode_mb(H264Context *h);

4
libavcodec/h264_cabac.c
View File

@ -2002,14 +2002,14 @@ decode_intra_mb:
ff_h264_write_back_intra_pred_mode(h);
if( ff_h264_check_intra4x4_pred_mode(h) < 0 ) return -1;
} else {
h->intra16x16_pred_mode= ff_h264_check_intra_pred_mode( h, h->intra16x16_pred_mode );
h->intra16x16_pred_mode= ff_h264_check_intra_pred_mode( h, h->intra16x16_pred_mode, 0 );
if( h->intra16x16_pred_mode < 0 ) return -1;
}
if(decode_chroma){
h->chroma_pred_mode_table[mb_xy] =
pred_mode = decode_cabac_mb_chroma_pre_mode( h );
pred_mode= ff_h264_check_intra_pred_mode( h, pred_mode );
pred_mode= ff_h264_check_intra_pred_mode( h, pred_mode, 1 );
if( pred_mode < 0 ) return -1;
h->chroma_pred_mode= pred_mode;
} else {

4
libavcodec/h264_cavlc.c
View File

@ -736,12 +736,12 @@ decode_intra_mb:
if( ff_h264_check_intra4x4_pred_mode(h) < 0)
return -1;
}else{
h->intra16x16_pred_mode= ff_h264_check_intra_pred_mode(h, h->intra16x16_pred_mode);
h->intra16x16_pred_mode= ff_h264_check_intra_pred_mode(h, h->intra16x16_pred_mode, 0);
if(h->intra16x16_pred_mode < 0)
return -1;
}
if(decode_chroma){
pred_mode= ff_h264_check_intra_pred_mode(h, get_ue_golomb_31(&s->gb));
pred_mode= ff_h264_check_intra_pred_mode(h, get_ue_golomb_31(&s->gb), 1);
if(pred_mode < 0)
return -1;
h->chroma_pred_mode= pred_mode;

4
libavcodec/svq3.c
View File

@ -610,7 +610,7 @@ static int svq3_decode_mb(SVQ3Context *svq3, unsigned int mb_type)
dir = i_mb_type_info[mb_type - 8].pred_mode;
dir = (dir >> 1) ^ 3*(dir & 1) ^ 1;
if ((h->intra16x16_pred_mode = ff_h264_check_intra_pred_mode(h, dir)) == -1){
if ((h->intra16x16_pred_mode = ff_h264_check_intra_pred_mode(h, dir, 0)) == -1){
av_log(h->s.avctx, AV_LOG_ERROR, "check_intra_pred_mode = -1\n");
return -1;
}
@ -709,7 +709,7 @@ static int svq3_decode_mb(SVQ3Context *svq3, unsigned int mb_type)
s->current_picture.mb_type[mb_xy] = mb_type;
if (IS_INTRA(mb_type)) {
h->chroma_pred_mode = ff_h264_check_intra_pred_mode(h, DC_PRED8x8);
h->chroma_pred_mode = ff_h264_check_intra_pred_mode(h, DC_PRED8x8, 1);
}
return 0;