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pngdec: don't use AV_PIX_FMT_MONOBLACK for apng 

AV_PIX_FMT_MONOBLACK has the AV_PIX_FMT_FLAG_BITSTREAM flag, i.e.
linesize can be smaller than width.

Since x_offset is only check against the width, this can lead to
x_offset * bpp >= image_linesize.

In this case ptr could be set to a position outside the image_buf in
png_handle_row, leading to memory corruption and thus crashes.

Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 372aa0777a)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Andreas Cadhalpun 2015-05-03 20:36:20 +02:00 committed by Michael Niedermayer
parent b04f6dfd3c
commit 9b12e4c1e3
1 changed files with 1 additions and 1 deletions
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2
libavcodec/pngdec.c
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@ -617,7 +617,7 @@ static int decode_idat_chunk(AVCodecContext *avctx, PNGDecContext *s,
} else if ((s->bits_per_pixel == 1 || s->bits_per_pixel == 2 || s->bits_per_pixel == 4 || s->bits_per_pixel == 8) &&
s->color_type == PNG_COLOR_TYPE_PALETTE) {
avctx->pix_fmt = AV_PIX_FMT_PAL8;
} else if (s->bit_depth == 1 && s->bits_per_pixel == 1) {
} else if (s->bit_depth == 1 && s->bits_per_pixel == 1 && avctx->codec_id != AV_CODEC_ID_APNG) {
avctx->pix_fmt = AV_PIX_FMT_MONOBLACK;
} else if (s->bit_depth == 8 &&
s->color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {