[binutils-gdb] Yet another out-of-memory fuzzed object

[Alan Modra <amodra@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=3b37f0f1b86cc1fb3ba9cc6d89695109db7f829a

commit 3b37f0f1b86cc1fb3ba9cc6d89695109db7f829a
Author: Alan Modra <amodra@gmail.com>
Date:   Wed Apr 19 22:32:15 2023 +0930

    Yet another out-of-memory fuzzed object
    
    Do I care about out of memory conditions triggered by fuzzers?  Not
    much.  Your operating system ought to be able to handle it by killing
    the memory hog.  Oh well, this one was an element of a coff-alpha
    archive that said it was a little less that 2**64 in size.  The
    coff-alpha compression scheme expands at most 8 times, so we can do
    better in bfd_get_file_size.
    
            * bfdio.c (bfd_get_file_size): Assume elements in compressed
            archive can only expand a maximum of eight times.
            * coffgen.c (_bfd_coff_get_external_symbols): Sanity check
            size of symbol table agains file size.

Diff:
---
 bfd/bfdio.c   |  9 +++++----
 bfd/coffgen.c | 10 ++++++++++
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/bfd/bfdio.c b/bfd/bfdio.c
index 337d4a10b66..990d349d428 100644
--- a/bfd/bfdio.c
+++ b/bfd/bfdio.c
@@ -524,6 +524,7 @@ ufile_ptr
 bfd_get_file_size (bfd *abfd)
 {
   ufile_ptr file_size, archive_size = (ufile_ptr) -1;
+  unsigned int compression_p2 = 0;
 
   if (abfd->my_archive != NULL
       && !bfd_is_thin_archive (abfd->my_archive))
@@ -532,17 +533,17 @@ bfd_get_file_size (bfd *abfd)
       if (adata != NULL)
 	{
 	  archive_size = adata->parsed_size;
-	  /* If the archive is compressed we can't compare against
-	     file size.  */
+	  /* If the archive is compressed, assume an element won't
+	     expand more than eight times file size.  */
 	  if (adata->arch_header != NULL
 	      && memcmp (((struct ar_hdr *) adata->arch_header)->ar_fmag,
 			 "Z\012", 2) == 0)
-	    return archive_size;
+	    compression_p2 = 3;
 	  abfd = abfd->my_archive;
 	}
     }
 
-  file_size = bfd_get_size (abfd);
+  file_size = bfd_get_size (abfd) << compression_p2;
   if (archive_size < file_size)
     return archive_size;
   return file_size;
diff --git a/bfd/coffgen.c b/bfd/coffgen.c
index 4725406b5ae..05f2640abe2 100644
--- a/bfd/coffgen.c
+++ b/bfd/coffgen.c
@@ -1551,6 +1551,7 @@ _bfd_coff_get_external_symbols (bfd *abfd)
   size_t symesz;
   size_t size;
   void * syms;
+  ufile_ptr filesize;
 
   if (obj_coff_external_syms (abfd) != NULL)
     return true;
@@ -1565,6 +1566,15 @@ _bfd_coff_get_external_symbols (bfd *abfd)
   if (size == 0)
     return true;
 
+  filesize = bfd_get_file_size (abfd);
+  if (filesize != 0
+      && ((ufile_ptr) obj_sym_filepos (abfd) > filesize
+	  || size > filesize - obj_sym_filepos (abfd)))
+    {
+      bfd_set_error (bfd_error_file_truncated);
+      return false;
+    }
+
   if (bfd_seek (abfd, obj_sym_filepos (abfd), SEEK_SET) != 0)
     return false;
   syms = _bfd_malloc_and_read (abfd, size, size);