PR26574, heap buffer overflow in _bfd_elf_slurp_secondary_reloc_section

PR26574, heap buffer overflow in _bfd_elf_slurp_secondary_reloc_section

[Alan Modra]

A horribly fuzzed object with section headers inside the ELF header.
Disallow that, and crazy reloc sizes.

	PR 26574
	* elfcode.h (elf_object_p): Sanity check section header offset.
	* elf.c (_bfd_elf_slurp_secondary_reloc_section): Sanity check
	sh_entsize.

diff --git a/bfd/elf.c b/bfd/elf.c
index ac2095f787..5a02f8dc30 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -12576,7 +12576,9 @@ _bfd_elf_slurp_secondary_reloc_section (bfd *      abfd,
       Elf_Internal_Shdr * hdr = & elf_section_data (relsec)->this_hdr;
 
       if (hdr->sh_type == SHT_SECONDARY_RELOC
-	  && hdr->sh_info == (unsigned) elf_section_data (sec)->this_idx)
+	  && hdr->sh_info == (unsigned) elf_section_data (sec)->this_idx
+	  && (hdr->sh_entsize == ebd->s->sizeof_rel
+	      || hdr->sh_entsize == ebd->s->sizeof_rela))
 	{
 	  bfd_byte * native_relocs;
 	  bfd_byte * native_reloc;
diff --git a/bfd/elfcode.h b/bfd/elfcode.h
index 2ed2f135c3..606ff64fd4 100644
--- a/bfd/elfcode.h
+++ b/bfd/elfcode.h
@@ -571,7 +571,7 @@ elf_object_p (bfd *abfd)
 
   /* If this is a relocatable file and there is no section header
      table, then we're hosed.  */
-  if (i_ehdrp->e_shoff == 0 && i_ehdrp->e_type == ET_REL)
+  if (i_ehdrp->e_shoff < sizeof (x_ehdr) && i_ehdrp->e_type == ET_REL)
     goto got_wrong_format_error;
 
   /* As a simple sanity check, verify that what BFD thinks is the
@@ -581,7 +581,7 @@ elf_object_p (bfd *abfd)
     goto got_wrong_format_error;
 
   /* Further sanity check.  */
-  if (i_ehdrp->e_shoff == 0 && i_ehdrp->e_shnum != 0)
+  if (i_ehdrp->e_shoff < sizeof (x_ehdr) && i_ehdrp->e_shnum != 0)
     goto got_wrong_format_error;
 
   ebd = get_elf_backend_data (abfd);
@@ -618,7 +618,7 @@ elf_object_p (bfd *abfd)
       && ebd->elf_osabi != ELFOSABI_NONE)
     goto got_wrong_format_error;
 
-  if (i_ehdrp->e_shoff != 0)
+  if (i_ehdrp->e_shoff >= sizeof (x_ehdr))
     {
       file_ptr where = (file_ptr) i_ehdrp->e_shoff;
 
@@ -819,7 +819,7 @@ elf_object_p (bfd *abfd)
 	}
     }
 
-  if (i_ehdrp->e_shstrndx != 0 && i_ehdrp->e_shoff != 0)
+  if (i_ehdrp->e_shstrndx != 0 && i_ehdrp->e_shoff >= sizeof (x_ehdr))
     {
       unsigned int num_sec;
 
-- 
2.17.1


-- 
Alan Modra
Australia Development Lab, IBM