PR24041, Invalid Memory Address Dereference in elf_link_add_object_symbols

PR 24041
	* elflink.c (elf_link_add_object_symbols): Don't segfault on
	crafted ET_DYN with no program headers.

bfd/ChangeLog

@@ -1,3 +1,9 @@
+2018-12-31  Alan Modra  <amodra@gmail.com>
+
+	PR 24041
+	* elflink.c (elf_link_add_object_symbols): Don't segfault on
+	crafted ET_DYN with no program headers.
+
 2018-12-31  Alan Modra  <amodra@gmail.com>
 
 	* elf64-ppc.c (ppc64_elf_relocate_section <tls_ldgd_opt>): When

bfd/elflink.c

@@ -4186,7 +4186,7 @@ error_free_dyn:
 	 all sections contained fully therein.  This makes relro
 	 shared library sections appear as they will at run-time.  */
       phdr = elf_tdata (abfd)->phdr + elf_elfheader (abfd)->e_phnum;
-      while (--phdr >= elf_tdata (abfd)->phdr)
+      while (phdr-- > elf_tdata (abfd)->phdr)
 	if (phdr->p_type == PT_GNU_RELRO)
 	  {
 	    for (s = abfd->sections; s != NULL; s = s->next)