More fixes for memory access violations exposed by fuzzed binaries.

	PR binutils/17512
	* dwarf.h (struct dwarf_section): Add user_data field.
	* dwarf.c (frame_need_space): Check for an over large register
	number.
	(display_debug_frames): Check the return value from
	frame_need_space.  Check for a CFA expression that is so long the
	start address wraps around.
	(debug_displays): Initialise the user_data field.
	* objdump.c (load_specific_debug_section): Save the BFD section
	pointer in the user_data field of the dwarf_section structure.
	(free_debug_section): Update BFD section data when freeing section
	contents.
	* readelf.c (load_specific_debug_section): Initialise the
	user_data field.

	* archive.c (do_slurp_coff_armap): Add range checks to prevent
	running off the end of the string table.
	* compress.c (bfd_get_full_section_contents): Return a NULL
	pointer for zero sized sections.  Do not attempt to copy a buffer
	onto itself.
	* elf-attrs.c (_bfd_elf_parse_attributes): Check for an empty
	header.  Add range checks to avoid running off the end of the
	section.
	* elf.c (bfd_elf_get_str_section): Seek before allocating so that
	if the seek fails, no memory is allocated.
	(bfd_elf_string_from_elf_section): Do not allocate a string from a
	non string section.  It only leads to trouble later on.
	(_bfd_elf_print_private_bfd_data): Check for there being too
	little external dynamic data.
	(bfd_section_from_shdr): Replace assertion with a failure mode.
	(bfd_section_from_shdr): When walking a loaded group section use
	the internal structure size, not the external size.  Check for the
	group section being empty.
	* elf32-i386.c (elf_i386_rtype_to_howto): Replace assertion with a
	failure mode.
	* elfcode.h (elf_slurp_reloc_table): Likewise.
	* reloc.c (bfd_perform_relocation): Avoid seg-fault if the howto
	parameter is NULL.

1 files changed, 17 insertions, 0 deletions

diff --git a/binutils/objdump.c b/binutils/objdump.c
index fdfa602..b13bf00 100644
--- a/binutils/objdump.c
+++ b/binutils/objdump.c
@@ -2280,6 +2280,7 @@ load_specific_debug_section (enum dwarf_section_display_enum debug,
   section->address = bfd_get_section_vma (abfd, sec);
   section->size = bfd_get_section_size (sec);
   section->start = NULL;
+  section->user_data = sec;
   ret = bfd_get_full_section_contents (abfd, sec, &section->start);
 
   if (! ret)
@@ -2346,6 +2347,22 @@ free_debug_section (enum dwarf_section_display_enum debug)
   if (section->start == NULL)
     return;
 
+  /* PR 17512: file: 0f67f69d.  */
+  if (section->user_data != NULL)
+    {
+      asection * sec = (asection *) section->user_data;
+
+      /* If we are freeing contents that are also pointed to by the BFD
+	 library's section structure then make sure to update those pointers
+	 too.  Otherwise, the next time we try to load data for this section
+	 we can end up using a stale pointer.  */
+      if (section->start == sec->contents)
+	{
+	  sec->contents = NULL;
+	  sec->flags &= ~ SEC_IN_MEMORY;
+	}
+    }
+
   free ((char *) section->start);
   section->start = NULL;
   section->address = 0;