e_shstrndx checks

[Alan Modra]

	PR 4496
	* elf.c (bfd_elf_string_from_elf_section): Return NULL on
	invalid shstrndx.
	(bfd_elf_get_str_section): Likewise.

Index: bfd/elf.c
===================================================================
RCS file: /cvs/src/src/bfd/elf.c,v
retrieving revision 1.387
diff -u -p -r1.387 elf.c
--- bfd/elf.c	10 May 2007 14:46:48 -0000	1.387
+++ bfd/elf.c	14 May 2007 04:11:37 -0000
@@ -252,7 +252,9 @@ bfd_elf_get_str_section (bfd *abfd, unsi
   bfd_size_type shstrtabsize;
 
   i_shdrp = elf_elfsections (abfd);
-  if (i_shdrp == 0 || i_shdrp[shindex] == 0)
+  if (i_shdrp == 0
+      || shindex >= elf_numsections (abfd)
+      || i_shdrp[shindex] == 0)
     return NULL;
 
   shstrtab = i_shdrp[shindex]->contents;
@@ -291,6 +293,9 @@ bfd_elf_string_from_elf_section (bfd *ab
   if (strindex == 0)
     return "";
 
+  if (elf_elfsections (abfd) == NULL || shindex >= elf_numsections (abfd))
+    return NULL;
+
   hdr = elf_elfsections (abfd)[shindex];
 
   if (hdr->contents == NULL

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre