Limit bogus archive parsed_size

[Alan Modra <amodra at gmail dot com>]

Archive element size is given by data in the archive, and thus is
subject to attack by fuzzers.  The only harm this allows is allocation
of huge amounts of memory, but some systems don't handle that well.
So limit archive element size to archive file size.

	* bfdio.c (bfd_get_file_size): Ignore bogus archive element sizes.

diff --git a/bfd/bfdio.c b/bfd/bfdio.c
index 49e0958526..71ac17ec51 100644
--- a/bfd/bfdio.c
+++ b/bfd/bfdio.c
@@ -25,6 +25,7 @@
 #include <limits.h>
 #include "bfd.h"
 #include "libbfd.h"
+#include "aout/ar.h"
 
 #ifndef S_IXUSR
 #define S_IXUSR 0100    /* Execute by owner.  */
@@ -460,11 +461,24 @@ DESCRIPTION
 ufile_ptr
 bfd_get_file_size (bfd *abfd)
 {
+  ufile_ptr file_size, archive_size = (ufile_ptr) -1;
+
   if (abfd->my_archive != NULL
       && !bfd_is_thin_archive (abfd->my_archive))
-    return arelt_size (abfd);
+    {
+      struct areltdata *adata = (struct areltdata *) abfd->arelt_data;
+      archive_size = adata->parsed_size;
+      /* If the archive is compressed we can't compare against file size.  */
+      if (memcmp (((struct ar_hdr *) adata->arch_header)->ar_fmag,
+		  "Z\012", 2) == 0)
+	return archive_size;
+      abfd = abfd->my_archive;
+    }
 
-  return bfd_get_size (abfd);
+  file_size = bfd_get_size (abfd);
+  if (archive_size < file_size)
+    return archive_size;
+  return file_size;
 }
 
 /*

-- 
Alan Modra
Australia Development Lab, IBM