[PATCH] libdw: Fix overflow warning on 32bit systems with GCC8 in dwarf_getsrclines.

[Mark Wielaard <mark@klomp.org>]

ndirs is read from the debug data and should be size checked before use.

https://sourceware.org/bugzilla/show_bug.cgi?id=23248

Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 libdw/ChangeLog           | 5 +++++
 libdw/dwarf_getsrclines.c | 6 ++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 5a33d9c..c304a3b 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,3 +1,8 @@
+2018-05-30  Mark Wielaard  <mark@klomp.org>
+
+	* libdw/dwarf_getsrclines.c (read_srclines): Change ndir and
+	ndirlist to size_t. Add check to see ndirlist doesn't overflow.
+
 2018-05-29  Mark Wielaard  <mark@klomp.org>
 
 	* dwarf_cuoffset.c (dwarf_cuoffset): Check die->cu is not NULL.
diff --git a/libdw/dwarf_getsrclines.c b/libdw/dwarf_getsrclines.c
index 2bf3098..790d4e4 100644
--- a/libdw/dwarf_getsrclines.c
+++ b/libdw/dwarf_getsrclines.c
@@ -154,7 +154,7 @@ read_srclines (Dwarf *dbg,
   int res = -1;
 
   size_t nfilelist = 0;
-  unsigned int ndirlist = 0;
+  size_t ndirlist = 0;
 
   /* If there are a large number of lines, files or dirs don't blow up
      the stack.  Stack allocate some entries, only dynamically malloc
@@ -299,7 +299,7 @@ read_srclines (Dwarf *dbg,
   };
 
   /* First count the entries.  */
-  unsigned int ndirs = 0;
+  size_t ndirs = 0;
   if (version < 5)
     {
       const unsigned char *dirp = linep;
@@ -359,6 +359,8 @@ read_srclines (Dwarf *dbg,
   ndirlist = ndirs;
   if (ndirlist >= MAX_STACK_DIRS)
     {
+      if (ndirlist > SIZE_MAX / sizeof (*dirarray))
+	goto no_mem;
       dirarray = (struct dirlist *) malloc (ndirlist * sizeof (*dirarray));
       if (unlikely (dirarray == NULL))
 	{
-- 
1.8.3.1