Test SEC_HAS_CONTENTS before reading section contents

bfd_malloc_and_get_section does size sanity checking before allocating
memory and reading contents.  These size checks are not done for bss
style sections, because they typically don't occupy file space and
thus can't be compared against file size.  However, if you are
expecting to look at something other than a whole lot of zeros, don't
allow fuzzers to avoid the size checking.

	* cofflink.c (process_embedded_commands): Don't look at
	sections without SEC_HAS_CONTENTS set.
	* cpu-arm.c (bfd_arm_update_notes): Likewise.
	(bfd_arm_get_mach_from_notes): Likewise.
	* elf-eh-frame.c (_bfd_elf_parse_eh_frame): Likewise.
	* elf-hppa.h (elf_hppa_sort_unwind): Likewise.
	* elf-m10300.c (mn10300_elf_relax_section): Likewise.
	* elf-sframe.c (_bfd_elf_parse_sframe): Likewise.
	* elf.c (_bfd_elf_print_private_bfd_data): Likewise.
	* elf32-arm.c (bfd_elf32_arm_process_before_allocation): Likewise.
	* elf32-avr.c (avr_elf32_load_property_records): Likewise.
	* elf32-ppc.c (_bfd_elf_ppc_set_arch): Likewise.
	(ppc_elf_get_synthetic_symtab, ppc_elf_relax_section): Likewise.
	* elf64-ppc.c (ppc64_elf_get_synthetic_symtab): Likewise.
	(opd_entry_value, ppc64_elf_edit_opd, ppc64_elf_edit_toc): Likewise.
	* elf64-x86-64.c (elf_x86_64_get_synthetic_symtab): Likewise.
	* elflink.c (elf_link_add_object_symbols): Likewise.
	(bfd_elf_get_bfd_needed_list): Likewise.
	* elfnn-aarch64.c (get_plt_type): Likewise.
	* elfxx-mips.c (_bfd_mips_elf_get_synthetic_symtab): Likewise.
	* linker.c (_bfd_handle_already_linked): Likewise.
	* opncls.c (bfd_get_debug_link_info_1): Likewise.
	(bfd_get_alt_debug_link_info, get_build_id): Likewise.
	* peXXigen.c (pe_print_idata, pe_print_pdata): Likewise.
	(_bfd_XX_print_ce_compressed_pdata, pe_print_reloc): Likewise.
	* pei-x86_64.c (pex64_bfd_print_pdata_section): Likewise.
	* stabs.c (_bfd_link_section_stabs): Likewise.
	(_bfd_discard_section_stabs): Likewise.
	* xcofflink.c (_bfd_xcoff_get_dynamic_symtab_upper_bound): Likewise.
	(_bfd_xcoff_canonicalize_dynamic_symtab): Likewise.
	(_bfd_xcoff_get_dynamic_reloc_upper_bound): Likewise.
	(_bfd_xcoff_canonicalize_dynamic_reloc): Likewise.
	(xcoff_link_add_dynamic_symbols): Likewise.
	(xcoff_link_check_dynamic_ar_symbols): Likewise.
	(bfd_xcoff_build_dynamic_sections): Likewise.

1 files changed, 28 insertions, 17 deletions

diff --git a/bfd/linker.c b/bfd/linker.c
index 4fb7a66..e57c9ee 100644
--- a/bfd/linker.c
+++ b/bfd/linker.c
@@ -2880,27 +2880,38 @@ _bfd_handle_already_linked (asection *sec,
 	   sec->owner, sec);
       else if (sec->size != 0)
 	{
-	  bfd_byte *sec_contents, *l_sec_contents = NULL;
-
-	  if (!bfd_malloc_and_get_section (sec->owner, sec, &sec_contents))
+	  bfd_byte *sec_contents, *l_sec_contents;
+
+	  if ((sec->flags & SEC_HAS_CONTENTS) == 0
+	      && (l->sec->flags & SEC_HAS_CONTENTS) == 0)
+	    ;
+	  else if ((sec->flags & SEC_HAS_CONTENTS) == 0
+		   || !bfd_malloc_and_get_section (sec->owner, sec,
+						   &sec_contents))
 	    info->callbacks->einfo
 	      /* xgettext:c-format */
 	      (_("%pB: could not read contents of section `%pA'\n"),
 	       sec->owner, sec);
-	  else if (!bfd_malloc_and_get_section (l->sec->owner, l->sec,
-						&l_sec_contents))
-	    info->callbacks->einfo
-	      /* xgettext:c-format */
-	      (_("%pB: could not read contents of section `%pA'\n"),
-	       l->sec->owner, l->sec);
-	  else if (memcmp (sec_contents, l_sec_contents, sec->size) != 0)
-	    info->callbacks->einfo
-	      /* xgettext:c-format */
-	      (_("%pB: duplicate section `%pA' has different contents\n"),
-	       sec->owner, sec);
-
-	  free (sec_contents);
-	  free (l_sec_contents);
+	  else if ((l->sec->flags & SEC_HAS_CONTENTS) == 0
+		   || !bfd_malloc_and_get_section (l->sec->owner, l->sec,
+						   &l_sec_contents))
+	    {
+	      info->callbacks->einfo
+		/* xgettext:c-format */
+		(_("%pB: could not read contents of section `%pA'\n"),
+		 l->sec->owner, l->sec);
+	      free (sec_contents);
+	    }
+	  else
+	    {
+	      if (memcmp (sec_contents, l_sec_contents, sec->size) != 0)
+		info->callbacks->einfo
+		  /* xgettext:c-format */
+		  (_("%pB: duplicate section `%pA' has different contents\n"),
+		   sec->owner, sec);
+	      free (l_sec_contents);
+	      free (sec_contents);
+	    }
 	}
       break;
     }