[freetype2] master 1655e00: Fix handling of invalid format 2 cmaps.

[Werner LEMBERG]

branch: master
commit 1655e00fced6d16187fe2b3494d562795b2addd7
Author: Werner Lemberg <address@hidden>
Commit: Werner Lemberg <address@hidden>

    Fix handling of invalid format 2 cmaps.
    
    The problem was introduced after the last release.
    
    Reported as
    
      https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=7828
    
    * src/sfnt/ttcmap.c (tt_cmap2_char_next): Avoid endless loop.
---
 ChangeLog         | 12 ++++++++++++
 src/sfnt/ttcmap.c |  7 +++++++
 2 files changed, 19 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index c3788a9..99fca5d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2018-03-13  Werner Lemberg  <address@hidden>
+
+       Fix handling of invalid format 2 cmaps.
+
+       The problem was introduced after the last release.
+
+       Reported as
+
+         https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=7828
+
+       * src/sfnt/ttcmap.c (tt_cmap2_char_next): Avoid endless loop.
+
 2018-04-17  Werner Lemberg  <address@hidden>
 
        [truetype] Integer overflow issues.
diff --git a/src/sfnt/ttcmap.c b/src/sfnt/ttcmap.c
index dcde869..71a3c1e 100644
--- a/src/sfnt/ttcmap.c
+++ b/src/sfnt/ttcmap.c
@@ -518,6 +518,13 @@
         FT_UInt   pos, idx;
 
 
+        if ( char_lo > start + count )
+        {
+          /* this happens only for a malformed cmap */
+          charcode = 0x100;
+          continue;
+        }
+
         if ( offset == 0 )
         {
           if ( charcode == 0x100 )