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Code Issues Releases Activity

lagarith: fix buffer overreads.

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Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org
This commit is contained in:
Ronald S. Bultje 2012-03-27 12:26:46 -07:00
parent c0b34e6148
commit 0a82f5275f
2 changed files with 54 additions and 25 deletions
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74
libavcodec/lagarith.c
View File

@ -247,24 +247,26 @@ static void lag_pred_line(LagarithContext *l, uint8_t *buf,
{
int L, TL;
/* Left pixel is actually prev_row[width] */
L = buf[width - stride - 1];
if (!line) {
/* Left prediction only for first line */
L = l->dsp.add_hfyu_left_prediction(buf + 1, buf + 1,
width - 1, buf[0]);
return;
} else if (line == 1) {
/* Second line, left predict first pixel, the rest of the line is median predicted
* NOTE: In the case of RGB this pixel is top predicted */
TL = l->avctx->pix_fmt == PIX_FMT_YUV420P ? buf[-stride] : L;
} else {
/* Top left is 2 rows back, last pixel */
TL = buf[width - (2 * stride) - 1];
}
/* Left pixel is actually prev_row[width] */
L = buf[width - stride - 1];
add_lag_median_prediction(buf, buf - stride, buf,
width, &L, &TL);
if (line == 1) {
/* Second line, left predict first pixel, the rest of the line is median predicted
* NOTE: In the case of RGB this pixel is top predicted */
TL = l->avctx->pix_fmt == PIX_FMT_YUV420P ? buf[-stride] : L;
} else {
/* Top left is 2 rows back, last pixel */
TL = buf[width - (2 * stride) - 1];
}
add_lag_median_prediction(buf, buf - stride, buf,
width, &L, &TL);
}
}
static int lag_decode_line(LagarithContext *l, lag_rac *rac,
@ -310,13 +312,13 @@ handle_zeros:
}
static int lag_decode_zero_run_line(LagarithContext *l, uint8_t *dst,
const uint8_t *src, int width,
int esc_count)
const uint8_t *src, const uint8_t *src_end,
int width, int esc_count)
{
int i = 0;
int count;
uint8_t zero_run = 0;
const uint8_t *start = src;
const uint8_t *src_start = src;
uint8_t mask1 = -(esc_count < 2);
uint8_t mask2 = -(esc_count < 3);
uint8_t *end = dst + (width - 2);
@ -333,6 +335,8 @@ output_zeros:
i = 0;
while (!zero_run && dst + i < end) {
i++;
if (src + i >= src_end)
return AVERROR_INVALIDDATA;
zero_run =
!(src[i] | (src[i + 1] & mask1) | (src[i + 2] & mask2));
}
@ -348,9 +352,10 @@ output_zeros:
} else {
memcpy(dst, src, i);
src += i;
dst += i;
}
}
return start - src;
return src_start - src;
}
@ -366,6 +371,7 @@ static int lag_decode_arith_plane(LagarithContext *l, uint8_t *dst,
int esc_count = src[0];
GetBitContext gb;
lag_rac rac;
const uint8_t *src_end = src + src_size;
rac.avctx = l->avctx;
l->zeros = 0;
@ -396,10 +402,16 @@ static int lag_decode_arith_plane(LagarithContext *l, uint8_t *dst,
esc_count -= 4;
if (esc_count > 0) {
/* Zero run coding only, no range coding. */
for (i = 0; i < height; i++)
src += lag_decode_zero_run_line(l, dst + (i * stride), src,
width, esc_count);
for (i = 0; i < height; i++) {
int res = lag_decode_zero_run_line(l, dst + (i * stride), src,
src_end, width, esc_count);
if (res < 0)
return res;
src += res;
}
} else {
if (src_size < width * height)
return AVERROR_INVALIDDATA; // buffer not big enough
/* Plane is stored uncompressed */
for (i = 0; i < height; i++) {
memcpy(dst + (i * stride), src, width);
@ -506,11 +518,19 @@ static int lag_decode_frame(AVCodecContext *avctx,
}
for (i = 0; i < planes; i++)
srcs[i] = l->rgb_planes + (i + 1) * l->rgb_stride * avctx->height - l->rgb_stride;
if (offset_ry >= buf_size ||
offset_gu >= buf_size ||
offset_bv >= buf_size ||
(planes == 4 && offs[3] >= buf_size)) {
av_log(avctx, AV_LOG_ERROR,
"Invalid frame offsets\n");
return AVERROR_INVALIDDATA;
}
for (i = 0; i < planes; i++)
lag_decode_arith_plane(l, srcs[i],
avctx->width, avctx->height,
-l->rgb_stride, buf + offs[i],
buf_size);
buf_size - offs[i]);
dst = p->data[0];
for (i = 0; i < planes; i++)
srcs[i] = l->rgb_planes + i * l->rgb_stride * avctx->height;
@ -544,15 +564,23 @@ static int lag_decode_frame(AVCodecContext *avctx,
return -1;
}
if (offset_ry >= buf_size ||
offset_gu >= buf_size ||
offset_bv >= buf_size) {
av_log(avctx, AV_LOG_ERROR,
"Invalid frame offsets\n");
return AVERROR_INVALIDDATA;
}
lag_decode_arith_plane(l, p->data[0], avctx->width, avctx->height,
p->linesize[0], buf + offset_ry,
buf_size);
buf_size - offset_ry);
lag_decode_arith_plane(l, p->data[2], avctx->width / 2,
avctx->height / 2, p->linesize[2],
buf + offset_gu, buf_size);
buf + offset_gu, buf_size - offset_gu);
lag_decode_arith_plane(l, p->data[1], avctx->width / 2,
avctx->height / 2, p->linesize[1],
buf + offset_bv, buf_size);
buf + offset_bv, buf_size - offset_bv);
break;
default:
av_log(avctx, AV_LOG_ERROR,

5
libavcodec/lagarithrac.c
View File

@ -32,15 +32,16 @@
void ff_lag_rac_init(lag_rac *l, GetBitContext *gb, int length)
{
int i, j;
int i, j, left;
/* According to reference decoder "1st byte is garbage",
* however, it gets skipped by the call to align_get_bits()
*/
align_get_bits(gb);
left = get_bits_left(gb) >> 3;
l->bytestream_start =
l->bytestream = gb->buffer + get_bits_count(gb) / 8;
l->bytestream_end = l->bytestream_start + length;
l->bytestream_end = l->bytestream_start + FFMIN(length, left);
l->range = 0x80;
l->low = *l->bytestream >> 1;