PR22307, Heap out of bounds read in _bfd_elf_parse_gnu_properties

When adding an unbounded increment to a pointer, you can't just check
against the end of the buffer but also must check that overflow
doesn't result in "negative" pointer movement.  Pointer comparisons
are signed.  Better, check the increment against the space left using
an unsigned comparison.

	PR 22307
	* elf-properties.c (_bfd_elf_parse_gnu_properties): Compare datasz
	against size left rather than comparing pointers.  Reorganise loop.

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 6f2c2b7..2373816 100644 (file)
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,5 +1,11 @@
 2017-10-17  Alan Modra  <amodra@gmail.com>
 
+       PR 22307
+       * elf-properties.c (_bfd_elf_parse_gnu_properties): Compare datasz
+       against size left rather than comparing pointers.  Reorganise loop.
+
+2017-10-17  Alan Modra  <amodra@gmail.com>
+
        PR 22306
        * aoutx.h (aout_get_external_symbols): Handle stringsize of zero,
        and error for any other size that doesn't cover the header word.

diff --git a/bfd/elf-properties.c b/bfd/elf-properties.c
index f367aa6..bfb106e 100644 (file)
--- a/bfd/elf-properties.c
+++ b/bfd/elf-properties.c
@@ -93,15 +93,20 @@ bad_size:
       return FALSE;
     }
 
-  while (1)
+  while (ptr != ptr_end)
     {
-      unsigned int type = bfd_h_get_32 (abfd, ptr);
-      unsigned int datasz = bfd_h_get_32 (abfd, ptr + 4);
+      unsigned int type;
+      unsigned int datasz;
       elf_property *prop;
 
+      if ((size_t) (ptr_end - ptr) < 8)
+       goto bad_size;
+
+      type = bfd_h_get_32 (abfd, ptr);
+      datasz = bfd_h_get_32 (abfd, ptr + 4);
       ptr += 8;
 
-      if ((ptr + datasz) > ptr_end)
+      if (datasz > (size_t) (ptr_end - ptr))
        {
          _bfd_error_handler
            (_("warning: %B: corrupt GNU_PROPERTY_TYPE (%ld) type (0x%x) datasz: 0x%x"),
@@ -183,11 +188,6 @@ bad_size:
 
 next:
       ptr += (datasz + (align_size - 1)) & ~ (align_size - 1);
-      if (ptr == ptr_end)
-       break;
-
-      if (ptr > (ptr_end - 8))
-       goto bad_size;
     }
 
   return TRUE;