[binutils-gdb] XCOFF archive sanity check

[Alan Modra]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=99b847478c35b64ffddaf7af53c348217d037cb2

commit 99b847478c35b64ffddaf7af53c348217d037cb2
Author: Alan Modra <amodra@gmail.com>
Date:   Sat Mar 18 16:34:08 2023 +1030

    XCOFF archive sanity check
    
    XCOFF archive elements are in a linked list.  Add a little more sanity
    checking.  This of course doesn't stop the fuzzers finding a way to
    make a loop, but this check is cheap.
    
            * coff-rs6000.c (_bfd_xcoff_openr_next_archived_file): Sanity
            check that next element isn't pointing back to the header.

Diff:
---
 bfd/coff-rs6000.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/bfd/coff-rs6000.c b/bfd/coff-rs6000.c
index 4b7b5d315df..735d434951e 100644
--- a/bfd/coff-rs6000.c
+++ b/bfd/coff-rs6000.c
@@ -1714,8 +1714,11 @@ _bfd_xcoff_openr_next_archived_file (bfd *archive, bfd *last_file)
 	  laststart -= SIZEOF_AR_HDR + arel->extra_size;
 	}
 
-      /* Sanity check that we aren't pointing into the previous element.  */
-      if (filestart != 0 && filestart >= laststart && filestart < lastend)
+      /* Sanity check that we aren't pointing into the previous element,
+	 or into the header.  */
+      if (filestart != 0
+	  && (filestart < SIZEOF_AR_FILE_HDR
+	      || (filestart >= laststart && filestart < lastend)))
 	{
 	  bfd_set_error (bfd_error_malformed_archive);
 	  return NULL;
@@ -1747,8 +1750,11 @@ _bfd_xcoff_openr_next_archived_file (bfd *archive, bfd *last_file)
 	  laststart -= SIZEOF_AR_HDR_BIG + arel->extra_size;
 	}
 
-      /* Sanity check that we aren't pointing into the previous element.  */
-      if (filestart != 0 && filestart >= laststart && filestart < lastend)
+      /* Sanity check that we aren't pointing into the previous element
+	 or into the header.  */
+      if (filestart != 0
+	  && (filestart < SIZEOF_AR_FILE_HDR_BIG
+	      || (filestart >= laststart && filestart < lastend)))
 	{
 	  bfd_set_error (bfd_error_malformed_archive);
 	  return NULL;