Commit: Fix seg-fault in dwarf.c:process_debug_info

[Nick Clifton]

Hi Guys,

  I recently discovered that I could not examine the debug info in the
  libc shared library without running into a null-pointer dereference:

    $ readelf -wi /lib64/libc.so.6
    [...]
    Segmentation fault (core dumped)

  The issue is code in process_debug_info() which checks for a negative
  rnglists_base without first testing to make sure that a value exists.
  So I am applying the patch below as an obvious fix for the problem.

Cheers
  Nick

diff --git a/binutils/dwarf.c b/binutils/dwarf.c
index 92a07e00e9b..ce508d0315f 100644
--- a/binutils/dwarf.c
+++ b/binutils/dwarf.c
@@ -4248,14 +4248,17 @@ process_debug_info (struct dwarf_section * section,
 			  compunit.cu_version,
 			  debug_info_p);
 
-	      /* This check was in place before, keep it.  */
-	      stemp = debug_info_p->rnglists_base;
-	      if (stemp < 0)
+	      if (debug_info_p)
 		{
-		  warn (_("CU @ %#" PRIx64 " has has a negative rnglists_base "
-			  "value of %#" PRIx64 " - treating as zero"),
-			debug_info_p->cu_offset, stemp);
-		  debug_info_p->rnglists_base = 0;
+		  /* This check was in place before, keep it.  */
+		  stemp = debug_info_p->rnglists_base;
+		  if (stemp < 0)
+		    {
+		      warn (_("CU @ %#" PRIx64 " has has a negative rnglists_base "
+			      "value of %#" PRIx64 " - treating as zero"),
+			    debug_info_p->cu_offset, stemp);
+		      debug_info_p->rnglists_base = 0;
+		    }
 		}
 	    }