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xxan: protect against chroma LUT overreads. 

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org
This commit is contained in:
Ronald S. Bultje 2012-03-10 11:57:17 -08:00
parent 5518827816
commit f77bfa8376
1 changed files with 8 additions and 6 deletions
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14
libavcodec/xxan.c
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@ -162,7 +162,7 @@ static int xan_decode_chroma(AVCodecContext *avctx, unsigned chroma_off)
int i, j;
const uint8_t *src, *src_end;
const uint8_t *table;
int mode, offset, dec_size;
int mode, offset, dec_size, table_size;
if (!chroma_off)
return 0;
@ -171,9 +171,11 @@ static int xan_decode_chroma(AVCodecContext *avctx, unsigned chroma_off)
return -1;
}
bytestream2_seek(&s->gb, chroma_off + 4, SEEK_SET);
mode = bytestream2_get_le16(&s->gb);
table = s->gb.buffer;
offset = bytestream2_get_le16(&s->gb) * 2;
mode = bytestream2_get_le16(&s->gb);
table = s->gb.buffer;
table_size = bytestream2_get_le16(&s->gb);
offset = table_size * 2;
table_size += 1;
if (offset >= bytestream2_get_bytes_left(&s->gb)) {
av_log(avctx, AV_LOG_ERROR, "Invalid chroma block offset\n");
@ -196,7 +198,7 @@ static int xan_decode_chroma(AVCodecContext *avctx, unsigned chroma_off)
for (j = 0; j < avctx->height >> 1; j++) {
for (i = 0; i < avctx->width >> 1; i++) {
val = *src++;
if (val) {
if (val && val < table_size) {
val = AV_RL16(table + (val << 1));
uval = (val >> 3) & 0xF8;
vval = (val >> 8) & 0xF8;
@ -216,7 +218,7 @@ static int xan_decode_chroma(AVCodecContext *avctx, unsigned chroma_off)
for (j = 0; j < avctx->height >> 2; j++) {
for (i = 0; i < avctx->width >> 1; i += 2) {
val = *src++;
if (val) {
if (val && val < table_size) {
val = AV_RL16(table + (val << 1));
uval = (val >> 3) & 0xF8;
vval = (val >> 8) & 0xF8;