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check width x channels overflow in pnm2png row_bytes #890

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check width x channels overflow in pnm2png row_bytes #890

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10 changes: 8 additions & 2 deletions contrib/pngminus/pnm2png.c
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Original file line number Diff line number Diff line change
Expand Up @@ -357,12 +357,18 @@ BOOL do_pnm2png (png_struct *png_ptr, png_info *info_ptr,
if (packed_bitmap)
{
/* row data is as many bytes as can fit width x channels x bit_depth */
row_bytes = (width * channels * bit_depth + 7) / 8;
png_uint_32 bits = (png_uint_32) channels * (png_uint_32) bit_depth;
if (width > ((png_uint_32) (-1) - 7) / bits)
return FALSE; /* width x channels x bit_depth would overflow */
row_bytes = (width * bits + 7) / 8;
}
else
{
/* row_bytes is the width x number of channels x (bit-depth / 8) */
row_bytes = width * channels * ((bit_depth <= 8) ? 1 : 2);
png_uint_32 bpp = (png_uint_32) channels * ((bit_depth <= 8) ? 1 : 2);
if (width > (png_uint_32) (-1) / bpp)
return FALSE; /* width x channels x depth would overflow */
row_bytes = width * bpp;
}

if ((row_bytes == 0) ||
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