avcodec/pngdec: Check deloco index more exactly

Fixes: out of array access:
Fixes: 48567/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PNG_fuzzer-6716193709096960

Alternatively it should be possible to limit this to 3 plane RGB 8 /16bit to ensure the size is what it should be

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2023-01-11 23:26:06 +01:00
parent 4dee46426e
commit d5bae70406
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@ -329,7 +329,7 @@ void ff_png_filter_row(PNGDSPContext *dsp, uint8_t *dst, int filter_type,
static void deloco_ ## NAME(TYPE *dst, int size, int alpha) \
{ \
int i; \
for (i = 0; i < size; i += 3 + alpha) { \
for (i = 0; i < size - 2; i += 3 + alpha) { \
int g = dst [i + 1]; \
dst[i + 0] += g; \
dst[i + 2] += g; \