[gimp] PCX: Avoid segmentation fault with invalid file.

[Jehan Pagès <jehanp src gnome org>]

commit 10f12bdcbd475b215a4d98a0db21c98debf872d5
Author: Tobias Stoeckmann <tobias stoeckmann org>
Date:   Thu Apr 6 21:37:50 2017 +0200

    PCX: Avoid segmentation fault with invalid file.
    
    If a PCX file contains a bytesperline entry which is too small, it is
    possible to trigger an out of boundary read, which can lead to a
    segmentation fault.
    
    The bytesperline validation is incomplete. While checking if enough
    bytes per line exist, the integer truncation during the division must be
    taken into account.
    
    An example would be a 1x1 PCX file with a bpp of 1 (monochrome). The
    current check allows a bytesperline field of 0, which in turn would lead
    to a 0 byte allocation in load_1. Yet, the code would access index 0.
    
    Signed-off-by: Tobias Stoeckmann <tobias stoeckmann org>

 plug-ins/common/file-pcx.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/plug-ins/common/file-pcx.c b/plug-ins/common/file-pcx.c
index fcda727..56267d7 100644
--- a/plug-ins/common/file-pcx.c
+++ b/plug-ins/common/file-pcx.c
@@ -409,7 +409,7 @@ load_image (const gchar  *filename,
       fclose (fd);
       return -1;
     }
-  if (bytesperline < (width * pcx_header.bpp) / 8)
+  if (bytesperline < ((width * pcx_header.bpp + 7) / 8))
     {
       g_message (_("Invalid number of bytes per line in PCX header"));
       fclose (fd);