Re: Invalid SHT_NOTE sections in input files

[Alan Modra <amodra at bigpond dot net dot au>]

On Tue, Jun 24, 2008 at 05:32:53PM -0400, Daniel Jacobowitz wrote:
> Since 2007-08-24 (build-id support), we parse note sections in any
> file opened by BFD - including linker input.  This shows up as an
> intermittent segfault in ld-elf/orphan, because four ld tests create
> invalid note sections (note-1, note-2, orphan, unknown).
> 
> This patch fixes the crash but adds four new failures as we detect the
> corrupt input.  Should we be more forgiving of invalid note sections?

Yes, I think we want the following.  I tweaked your patch a little so
that a sizes like -1 wouldn't sneak through the test by being rounded
up to 0.  I'm going to be away for 10 days so won't commit this.  If
it passes your scrutiny, please commit.

	* elf.c (_bfd_elf_make_section_from_shdr): Ignore return from
	elf_parse_notes.  Use bfd_malloc_and_get_section.
	(elf_parse_notes): Validate note namesz and descsz.

Index: bfd/elf.c
===================================================================
RCS file: /cvs/src/src/bfd/elf.c,v
retrieving revision 1.450
diff -u -p -r1.450 elf.c
--- bfd/elf.c	30 Jun 2008 20:53:06 -0000	1.450
+++ bfd/elf.c	8 Jul 2008 11:05:16 -0000
@@ -928,20 +928,12 @@ _bfd_elf_make_section_from_shdr (bfd *ab
      PT_NOTEs from the core files are currently not parsed using BFD.  */
   if (hdr->sh_type == SHT_NOTE)
     {
-      char *contents;
+      bfd_byte *contents;
 
-      contents = bfd_malloc (hdr->sh_size);
-      if (!contents)
+      if (!bfd_malloc_and_get_section (abfd, newsect, &contents))
 	return FALSE;
 
-      if (!bfd_get_section_contents (abfd, hdr->bfd_section, contents, 0,
-				     hdr->sh_size)
-	  || !elf_parse_notes (abfd, contents, hdr->sh_size, -1))
-	{
-	  free (contents);
-	  return FALSE;
-	}
-      
+      elf_parse_notes (abfd, (char *) contents, hdr->sh_size, -1);
       free (contents);
     }
 
@@ -8481,14 +8473,21 @@ elf_parse_notes (bfd *abfd, char *buf, s
       Elf_External_Note *xnp = (Elf_External_Note *) p;
       Elf_Internal_Note in;
 
+      if (p + sizeof (Elf_External_Note) > buf + size)
+	return FALSE;
+
       in.type = H_GET_32 (abfd, xnp->type);
 
       in.namesz = H_GET_32 (abfd, xnp->namesz);
       in.namedata = xnp->name;
+      if (in.namesz > (buf - in.namedata) + size)
+	return FALSE;
 
       in.descsz = H_GET_32 (abfd, xnp->descsz);
       in.descdata = in.namedata + BFD_ALIGN (in.namesz, 4);
       in.descpos = offset + (in.descdata - buf);
+      if (in.descsz > (buf - in.descdata) + size)
+	return FALSE;
 
       switch (bfd_get_format (abfd))
         {

-- 
Alan Modra
Australia Development Lab, IBM