readelf looping in process_archive

[Alan Modra]

With a crafted "negative" ar_hdr.ar_size it is possible to make
readelf loop.  This patch catches the overflow in a file offset
calculation.

	* readelf.c (process_archive): Prevent endless loop.

diff --git a/binutils/readelf.c b/binutils/readelf.c
index 1f0f49222f..9bc15e4d0b 100644
--- a/binutils/readelf.c
+++ b/binutils/readelf.c
@@ -20505,11 +20505,13 @@ process_archive (Filedata * filedata, bfd_boolean is_thin_archive)
 	{
 	  free (name);
 	  archive_file_offset = arch.next_arhdr_offset;
-	  arch.next_arhdr_offset += archive_file_size;
-
 	  filedata->file_name = qualified_name;
 	  if (! process_object (filedata))
 	    ret = FALSE;
+	  arch.next_arhdr_offset += archive_file_size;
+	  /* Stop looping with "negative" archive_file_size.  */
+	  if (arch.next_arhdr_offset < archive_file_size)
+	    break;
 	}
 
       free (qualified_name);

-- 
Alan Modra
Australia Development Lab, IBM