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Fix integer overflow in pnm2png height*sizeof(png_byte*) allocation #4

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Fix integer overflow in pnm2png height*sizeof(png_byte*) allocation #4

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5 changes: 5 additions & 0 deletions pngminus/pnm2png.c
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Original file line number Diff line number Diff line change
Expand Up @@ -375,6 +375,11 @@ BOOL do_pnm2png (png_struct *png_ptr, png_info *info_ptr,
/* allocate the rows using the same memory layout as libpng, and transfer
* their ownership to libpng, with the responsibility to clean everything up;
* please note the use of png_calloc instead of png_malloc */
/* Guard against integer overflow: height * sizeof(png_byte*) can wrap on
* 32-bit systems when height is large, producing a tiny allocation that
* subsequent writes overrun. */
if (height > PNG_SIZE_MAX / sizeof (png_byte *))
png_error (png_ptr, "image height too large for row-pointer allocation");
row_pointers = (png_byte **)
png_calloc (png_ptr, height * sizeof (png_byte *));
png_set_rows (png_ptr, info_ptr, row_pointers);
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