PR17910 sym string offset check

PR17910 sym string offset check

[Alan Modra]

As far as I can see the only place that sets obj_coff_strings without
setting obj_coff_strings_len is pe_ILF_build_a_bfd.  Fix that and we
can simplify the sym string offset check.  This is just a tidy.
pe_ILF_build_a_bfd doesn't create bad symbols and
_bfd_coff_read_string_table will always result in non-zero
obj_coff_strings_len when obj_coff_strings is non-NULL.

This patch came about because I was trying to track down an
uninitialised memory access and wondered if in some cases
_bfd_coff_internal_syment_name was allowing wild string offsets by
omitting the check.  It turns out it wasn't, but this way someone
looking at the code won't need to check further.

	PR 17910
	* coffgen.c (_bfd_coff_internal_syment_name): Always sanity
	check sym string offset.
	* peicode.h (pe_ILF_build_a_bfd): Set obj_coff_strings_len.

diff --git a/bfd/coffgen.c b/bfd/coffgen.c
index f21cf2ca523..774edf76f24 100644
--- a/bfd/coffgen.c
+++ b/bfd/coffgen.c
@@ -443,10 +443,7 @@ _bfd_coff_internal_syment_name (bfd *abfd,
 	  if (strings == NULL)
 	    return NULL;
 	}
-      /* PR 17910: Only check for string overflow if the length has been set.
-	 Some DLLs, eg those produced by Visual Studio, may not set the length field.  */
-      if (obj_coff_strings_len (abfd) > 0
-	  && sym->_n._n_n._n_offset >= obj_coff_strings_len (abfd))
+      if (sym->_n._n_n._n_offset >= obj_coff_strings_len (abfd))
 	return NULL;
       return strings + sym->_n._n_n._n_offset;
     }
diff --git a/bfd/peicode.h b/bfd/peicode.h
index b7b4f4abbb9..f1f3ce81533 100644
--- a/bfd/peicode.h
+++ b/bfd/peicode.h
@@ -1147,6 +1147,7 @@ pe_ILF_build_a_bfd (bfd *	    abfd,
   obj_conv_table_size (abfd) = vars.sym_index;
 
   obj_coff_strings (abfd) = vars.string_table;
+  obj_coff_strings_len (abfd) = vars.string_ptr - vars.string_table;
   obj_coff_keep_strings (abfd) = true;
 
   return true;

-- 
Alan Modra
Australia Development Lab, IBM