Fix seg fault objdumping a corrupt binary with an invalid sh_link field.

	PR binutils/20063
	* elf.c (bfd_elf_get_elf_syms): Check for out of range sh_link
	field before accessing sections array.

	* readelf.c (get_32bit_section_headers): Warn if an out of range
	sh_link or sh_info field is encountered.
	(get_64bit_section_headers): Likewise.

1 files changed, 11 insertions, 5 deletions

diff --git a/bfd/elf.c b/bfd/elf.c
index 4be7d73..1592183 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -407,11 +407,17 @@ bfd_elf_get_elf_syms (bfd *ibfd,
 
       /* Find an index section that is linked to this symtab section.  */
       for (entry = elf_symtab_shndx_list (ibfd); entry != NULL; entry = entry->next)
-	if (sections[entry->hdr.sh_link] == symtab_hdr)
-	  {
-	    shndx_hdr = & entry->hdr;
-	    break;
-	  };
+	{
+	  /* PR 20063.  */
+	  if (entry->hdr.sh_link >= elf_numsections (ibfd))
+	    continue;
+
+	  if (sections[entry->hdr.sh_link] == symtab_hdr)
+	    {
+	      shndx_hdr = & entry->hdr;
+	      break;
+	    };
+	}
 
       if (shndx_hdr == NULL)
 	{