Fix null pointer dereferences when using a link built with clang.

	PR binutils/21342
	* elflink.c (_bfd_elf_define_linkage_sym): Prevent null pointer
	dereference.
	(bfd_elf_final_link): Only initialize the extended symbol index
	section if there are extended symbol tables to list.

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index c676e6d..accb6d4 100644 (file)
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,11 @@
+2017-04-04  Nick Clifton  <nickc@redhat.com>
+
+       PR binutils/21342
+       * elflink.c (_bfd_elf_define_linkage_sym): Prevent null pointer
+       dereference.
+       (bfd_elf_final_link): Only initialize the extended symbol index
+       section if there are extended symbol tables to list.
+
 2017-04-03  H.J. Lu  <hongjiu.lu@intel.com>
 
        * Makefile.am (BFD32_BACKENDS): Add elf-properties.lo.

diff --git a/bfd/elflink.c b/bfd/elflink.c
index 776357f..9bf75c8 100644 (file)
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -119,15 +119,18 @@ _bfd_elf_define_linkage_sym (bfd *abfd,
         defined in shared libraries can't be overridden, because we
         lose the link to the bfd which is via the symbol section.  */
       h->root.type = bfd_link_hash_new;
+      bh = &h->root;
     }
+  else
+    bh = NULL;
 
-  bh = &h->root;
   bed = get_elf_backend_data (abfd);
   if (!_bfd_generic_link_add_one_symbol (info, abfd, name, BSF_GLOBAL,
                                         sec, 0, NULL, FALSE, bed->collect,
                                         &bh))
     return NULL;
   h = (struct elf_link_hash_entry *) bh;
+  BFD_ASSERT (h != NULL);
   h->def_regular = 1;
   h->non_elf = 0;
   h->root.linker_def = 1;
@@ -12038,24 +12041,28 @@ bfd_elf_final_link (bfd *abfd, struct bfd_link_info *info)
     {
       /* Finish up and write out the symbol string table (.strtab)
         section.  */
-      Elf_Internal_Shdr *symstrtab_hdr;
+      Elf_Internal_Shdr *symstrtab_hdr = NULL;
       file_ptr off = symtab_hdr->sh_offset + symtab_hdr->sh_size;
 
-      symtab_shndx_hdr = & elf_symtab_shndx_list (abfd)->hdr;
-      if (symtab_shndx_hdr != NULL && symtab_shndx_hdr->sh_name != 0)
+      if (elf_symtab_shndx_list (abfd))
        {
-         symtab_shndx_hdr->sh_type = SHT_SYMTAB_SHNDX;
-         symtab_shndx_hdr->sh_entsize = sizeof (Elf_External_Sym_Shndx);
-         symtab_shndx_hdr->sh_addralign = sizeof (Elf_External_Sym_Shndx);
-         amt = bfd_get_symcount (abfd) * sizeof (Elf_External_Sym_Shndx);
-         symtab_shndx_hdr->sh_size = amt;
+         symtab_shndx_hdr = & elf_symtab_shndx_list (abfd)->hdr;
 
-         off = _bfd_elf_assign_file_position_for_section (symtab_shndx_hdr,
-                                                          off, TRUE);
+         if (symtab_shndx_hdr != NULL && symtab_shndx_hdr->sh_name != 0)
+           {
+             symtab_shndx_hdr->sh_type = SHT_SYMTAB_SHNDX;
+             symtab_shndx_hdr->sh_entsize = sizeof (Elf_External_Sym_Shndx);
+             symtab_shndx_hdr->sh_addralign = sizeof (Elf_External_Sym_Shndx);
+             amt = bfd_get_symcount (abfd) * sizeof (Elf_External_Sym_Shndx);
+             symtab_shndx_hdr->sh_size = amt;
 
-         if (bfd_seek (abfd, symtab_shndx_hdr->sh_offset, SEEK_SET) != 0
-             || (bfd_bwrite (flinfo.symshndxbuf, amt, abfd) != amt))
-           return FALSE;
+             off = _bfd_elf_assign_file_position_for_section (symtab_shndx_hdr,
+                                                              off, TRUE);
+
+             if (bfd_seek (abfd, symtab_shndx_hdr->sh_offset, SEEK_SET) != 0
+                 || (bfd_bwrite (flinfo.symshndxbuf, amt, abfd) != amt))
+               return FALSE;
+           }
        }
 
       symstrtab_hdr = &elf_tdata (abfd)->strtab_hdr;