From 3cfd62d77c2a7e147a05bd678524c345fa9c2bb8 Mon Sep 17 00:00:00 2001
From: erouault <erouault>
Date: Wed, 11 Jan 2017 13:28:01 +0000
Subject: [PATCH] * libtiff/tif_dirread.c: avoid division by floating point 0
 in TIFFReadDirEntryCheckedRational() and TIFFReadDirEntryCheckedSrational(),
 and return 0 in that case (instead of infinity as before presumably)
 Apparently some sanitizers do not like those divisions by zero. Fixes
 http://bugzilla.maptools.org/show_bug.cgi?id=2644

Fixes CVE-2017-7598

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
---
 libtiff/tif_dirread.c | 10 ++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/libtiff/tif_dirread.c b/libtiff/tif_dirread.c
index 570d0c32..8a1e42aa 100644
--- a/libtiff/tif_dirread.c
+++ b/libtiff/tif_dirread.c
@@ -2872,7 +2872,10 @@ static enum TIFFReadDirEntryErr TIFFReadDirEntryCheckedRational(TIFF* tif, TIFFD
 		m.l = direntry->tdir_offset.toff_long8;
 	if (tif->tif_flags&TIFF_SWAB)
 		TIFFSwabArrayOfLong(m.i,2);
-	if (m.i[0]==0)
+        /* Not completely sure what we should do when m.i[1]==0, but some */
+        /* sanitizers do not like division by 0.0: */
+        /* http://bugzilla.maptools.org/show_bug.cgi?id=2644 */
+	if (m.i[0]==0 || m.i[1]==0)
 		*value=0.0;
 	else
 		*value=(double)m.i[0]/(double)m.i[1];
@@ -2900,7 +2903,10 @@ static enum TIFFReadDirEntryErr TIFFReadDirEntryCheckedSrational(TIFF* tif, TIFF
 		m.l=direntry->tdir_offset.toff_long8;
 	if (tif->tif_flags&TIFF_SWAB)
 		TIFFSwabArrayOfLong(m.i,2);
-	if ((int32)m.i[0]==0)
+        /* Not completely sure what we should do when m.i[1]==0, but some */
+        /* sanitizers do not like division by 0.0: */
+        /* http://bugzilla.maptools.org/show_bug.cgi?id=2644 */
+	if ((int32)m.i[0]==0 || m.i[1]==0)
 		*value=0.0;
 	else
 		*value=(double)((int32)m.i[0])/(double)m.i[1];
-- 
2.11.0