Fix undefined behavior in libpng

Check for a null source before calling memcpy.

BUG=skia:5390
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2040433002

Review-Url: https://codereview.chromium.org/2040433002
This commit is contained in:
scroggo 2016-06-03 09:36:53 -07:00 committed by Commit bot
parent 7b9eabb392
commit 1915b0bab2
2 changed files with 12 additions and 0 deletions

View File

@ -9,3 +9,4 @@ Local Modifications:
(2) Included Intel optimizations by running:
"patch -i contrib/intel/intel_sse.patch -p1"
(3) Removed files unused by Skia
(4) Fixed an undefined behavior bug (skbug.com/5390)

View File

@ -499,7 +499,18 @@ png_push_save_buffer(png_structrp png_ptr)
png_error(png_ptr, "Insufficient memory for save_buffer");
}
#if 0
// This is the code checked into libpng. Calling memcpy with a null
// source is undefined, even if count is 0, but libpng does not
// currently check for null or 0. The Skia fix is below.
// skbug.com/5390
memcpy(png_ptr->save_buffer, old_buffer, png_ptr->save_buffer_size);
#else
if (old_buffer)
memcpy(png_ptr->save_buffer, old_buffer, png_ptr->save_buffer_size);
else if (png_ptr->save_buffer_size)
png_error(png_ptr, "save_buffer error");
#endif
png_free(png_ptr, old_buffer);
png_ptr->save_buffer_max = new_max;
}