[FFmpeg-devel] [PATCH 2/7] Check for out of bound accesses in the 4xm decoder.
fenrir at elivagar.org
fenrir at elivagar.org
Sun Oct 2 00:38:27 CEST 2011
From: Laurent Aimar <fenrir at videolan.org>
---
libavcodec/4xm.c | 59 ++++++++++++++++++++++++++++++++++++++++++-----------
1 files changed, 46 insertions(+), 13 deletions(-)
diff --git a/libavcodec/4xm.c b/libavcodec/4xm.c
index cf98e91..f452114 100644
--- a/libavcodec/4xm.c
+++ b/libavcodec/4xm.c
@@ -133,7 +133,9 @@ typedef struct FourXContext{
GetBitContext pre_gb; ///< ac/dc prefix
GetBitContext gb;
const uint8_t *bytestream;
+ const uint8_t *bytestream_end;
const uint16_t *wordstream;
+ const uint16_t *wordstream_end;
int mv[256];
VLC pre_vlc;
int last_dc;
@@ -328,6 +330,8 @@ static void decode_p_block(FourXContext *f, uint16_t *dst, uint16_t *src, int lo
assert(code>=0 && code<=6);
if(code == 0){
+ if (f->bytestream_end - f->bytestream < 1)
+ return;
src += f->mv[ *f->bytestream++ ];
if(start > src || src > end){
av_log(f->avctx, AV_LOG_ERROR, "mv out of pic\n");
@@ -345,15 +349,23 @@ static void decode_p_block(FourXContext *f, uint16_t *dst, uint16_t *src, int lo
}else if(code == 3 && f->version<2){
mcdc(dst, src, log2w, h, stride, 1, 0);
}else if(code == 4){
+ if (f->bytestream_end - f->bytestream < 1)
+ return;
src += f->mv[ *f->bytestream++ ];
if(start > src || src > end){
av_log(f->avctx, AV_LOG_ERROR, "mv out of pic\n");
return;
}
+ if (f->wordstream_end - f->wordstream < 1)
+ return;
mcdc(dst, src, log2w, h, stride, 1, av_le2ne16(*f->wordstream++));
}else if(code == 5){
+ if (f->wordstream_end - f->wordstream < 1)
+ return;
mcdc(dst, src, log2w, h, stride, 0, av_le2ne16(*f->wordstream++));
}else if(code == 6){
+ if (f->wordstream_end - f->wordstream < 2)
+ return;
if(log2w){
dst[0] = av_le2ne16(*f->wordstream++);
dst[1] = av_le2ne16(*f->wordstream++);
@@ -375,6 +387,8 @@ static int decode_p_frame(FourXContext *f, const uint8_t *buf, int length){
if(f->version>1){
extra=20;
+ if (length < extra)
+ return -1;
bitstream_size= AV_RL32(buf+8);
wordstream_size= AV_RL32(buf+12);
bytestream_size= AV_RL32(buf+16);
@@ -385,11 +399,10 @@ static int decode_p_frame(FourXContext *f, const uint8_t *buf, int length){
bytestream_size= FFMAX(length - bitstream_size - wordstream_size, 0);
}
- if(bitstream_size+ bytestream_size+ wordstream_size + extra != length
- || bitstream_size > (1<<26)
- || bytestream_size > (1<<26)
- || wordstream_size > (1<<26)
- ){
+ if (bitstream_size > length ||
+ bytestream_size > length - bitstream_size ||
+ wordstream_size > length - bytestream_size - bitstream_size ||
+ extra > length - bytestream_size - bitstream_size - wordstream_size){
av_log(f->avctx, AV_LOG_ERROR, "lengths %d %d %d %d\n", bitstream_size, bytestream_size, wordstream_size,
bitstream_size+ bytestream_size+ wordstream_size - length);
return -1;
@@ -402,7 +415,9 @@ static int decode_p_frame(FourXContext *f, const uint8_t *buf, int length){
init_get_bits(&f->gb, f->bitstream_buffer, 8*bitstream_size);
f->wordstream= (const uint16_t*)(buf + extra + bitstream_size);
+ f->wordstream_end= f->wordstream + wordstream_size/2;
f->bytestream= buf + extra + bitstream_size + wordstream_size;
+ f->bytestream_end = f->bytestream + bytestream_size;
init_mv(f);
@@ -531,7 +546,7 @@ static int decode_i_mb(FourXContext *f){
return 0;
}
-static const uint8_t *read_huffman_tables(FourXContext *f, const uint8_t * const buf){
+static const uint8_t *read_huffman_tables(FourXContext *f, const uint8_t * const buf, int buf_size){
int frequency[512];
uint8_t flag[512];
int up[512];
@@ -539,6 +554,7 @@ static const uint8_t *read_huffman_tables(FourXContext *f, const uint8_t * const
int bits_tab[257];
int start, end;
const uint8_t *ptr= buf;
+ const uint8_t *ptr_end = buf + buf_size;
int j;
memset(frequency, 0, sizeof(frequency));
@@ -549,6 +565,8 @@ static const uint8_t *read_huffman_tables(FourXContext *f, const uint8_t * const
for(;;){
int i;
+ if (start <= end && ptr_end - ptr < end - start + 1 + 1)
+ return NULL;
for(i=start; i<=end; i++){
frequency[i]= *ptr++;
}
@@ -621,10 +639,13 @@ static int decode_i2_frame(FourXContext *f, const uint8_t *buf, int length){
const int height= f->avctx->height;
uint16_t *dst= (uint16_t*)f->current_picture.data[0];
const int stride= f->current_picture.linesize[0]>>1;
+ const uint8_t *buf_end = buf + length;
for(y=0; y<height; y+=16){
for(x=0; x<width; x+=16){
unsigned int color[4], bits;
+ if (buf_end - buf < 8)
+ return -1;
memset(color, 0, sizeof(color));
//warning following is purely guessed ...
color[0]= bytestream_get_le16(&buf);
@@ -658,18 +679,23 @@ static int decode_i_frame(FourXContext *f, const uint8_t *buf, int length){
uint16_t *dst= (uint16_t*)f->current_picture.data[0];
const int stride= f->current_picture.linesize[0]>>1;
const unsigned int bitstream_size= AV_RL32(buf);
- const int token_count av_unused = AV_RL32(buf + bitstream_size + 8);
- unsigned int prestream_size= 4*AV_RL32(buf + bitstream_size + 4);
- const uint8_t *prestream= buf + bitstream_size + 12;
+ unsigned int prestream_size;
+ const uint8_t *prestream;
+
+ if (bitstream_size > (1<<26) || length < bitstream_size + 12)
+ return -1;
+ prestream_size = 4*AV_RL32(buf + bitstream_size + 4);
+ prestream = buf + bitstream_size + 12;
- if(prestream_size + bitstream_size + 12 != length
- || bitstream_size > (1<<26)
- || prestream_size > (1<<26)){
+ if (prestream_size > (1<<26) ||
+ prestream_size != length - (bitstream_size + 12)){
av_log(f->avctx, AV_LOG_ERROR, "size mismatch %d %d %d\n", prestream_size, bitstream_size, length);
return -1;
}
- prestream= read_huffman_tables(f, prestream);
+ prestream= read_huffman_tables(f, prestream, buf + length - prestream);
+ if (!prestream)
+ return -1;
init_get_bits(&f->gb, buf + 4, 8*bitstream_size);
@@ -710,6 +736,8 @@ static int decode_frame(AVCodecContext *avctx,
AVFrame *p, temp;
int i, frame_4cc, frame_size;
+ if (buf_size < 12)
+ return AVERROR_INVALIDDATA;
frame_4cc= AV_RL32(buf);
if(buf_size != AV_RL32(buf+4)+8 || buf_size < 20){
av_log(f->avctx, AV_LOG_ERROR, "size mismatch %d %d\n", buf_size, AV_RL32(buf+4));
@@ -722,6 +750,9 @@ static int decode_frame(AVCodecContext *avctx,
const int whole_size= AV_RL32(buf+16);
CFrameBuffer *cfrm;
+ if (data_size < 0 || whole_size < 0)
+ return AVERROR_INVALIDDATA;
+
for(i=0; i<CFRAME_BUFFER_COUNT; i++){
if(f->cfrm[i].id && f->cfrm[i].id < avctx->frame_number)
av_log(f->avctx, AV_LOG_ERROR, "lost c frame %d\n", f->cfrm[i].id);
@@ -738,6 +769,8 @@ static int decode_frame(AVCodecContext *avctx,
}
cfrm= &f->cfrm[i];
+ if (data_size > UINT_MAX - cfrm->size - FF_INPUT_BUFFER_PADDING_SIZE)
+ return AVERROR_INVALIDDATA;
cfrm->data= av_fast_realloc(cfrm->data, &cfrm->allocated_size, cfrm->size + data_size + FF_INPUT_BUFFER_PADDING_SIZE);
if(!cfrm->data){ //explicit check needed as memcpy below might not catch a NULL
av_log(f->avctx, AV_LOG_ERROR, "realloc falure");
--
1.7.2.5
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