GraphicsMagick heap out of bounds write issue

[Bob Friesenhahn <bfriesen () simple dallas tx us>]

GraphicsMagick versions up to 1.3.25 encounter a write beyond an 
allocated heap buffer when reading CMYKA TIFF files which claim to 
offer fewer samples per pixel than required.

This is the tiffinfo description of the problematic TIFF file:

TIFF Directory at offset 0x808 (2056)
  Image Width: 34 Image Length: 48
  Bits/Sample: 8
  Sample Format: unsigned integer
  Compression Scheme: None
  Photometric Interpretation: separated
  Extra Samples: 1<unassoc-alpha>
  Orientation: row 0 top, col 0 lhs
  Samples/Pixel: 2
  Rows/Strip: 32
  Planar Configuration: single image plane

The fix for this is Mercurial changeset 14998:6156b4c2992d which may 
be viewed at SourceForge via this link:

https://sourceforge.net/p/graphicsmagick/code/ci/6156b4c2992d855ece6079653b3b93c3229fc4b8/

A minimal patch to correct the problem is attached.

This issue was reported to us on February 15, 2017 by Valon Chu.

Bob
--
Bob Friesenhahn
bfriesen () simple dallas tx us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

Attachment: tiff.c.patch
Description: