PR22047, Heap out of bounds read in parse_comp_unit

Like the PR22230 fix, we can allocate a buffer with an extra byte
rather than letting bfd_simple_get_relocated_section_contents malloc
and return a buffer.  Much better than allocating another buffer
afterwards.

	PR 22047
	* dwarf2.c (read_section): Allocate buffer with extra byte for
	bfd_simple_get_relocated_section_contents rather than copying
	afterwards.

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 8b44ceb..9a6af67 100644 (file)
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,10 @@
+2017-10-01  Alan Modra  <amodra@gmail.com>
+
+       PR 22047
+       * dwarf2.c (read_section): Allocate buffer with extra byte for
+       bfd_simple_get_relocated_section_contents rather than copying
+       afterwards.
+
 2017-09-29  Alan Modra  <amodra@gmail.com>
 
        * merge.c (merge_strings): Return FALSE on malloc failure.

diff --git a/bfd/dwarf2.c b/bfd/dwarf2.c
index be415e3..4cf50cc 100644 (file)
--- a/bfd/dwarf2.c
+++ b/bfd/dwarf2.c
@@ -526,9 +526,10 @@ read_section (bfd *           abfd,
 {
   asection *msec;
   const char *section_name = sec->uncompressed_name;
+  bfd_byte *contents = *section_buffer;
 
   /* The section may have already been read.  */
-  if (*section_buffer == NULL)
+  if (contents == NULL)
     {
       msec = bfd_get_section_by_name (abfd, section_name);
       if (! msec)
@@ -546,45 +547,21 @@ read_section (bfd *           abfd,
        }
 
       *section_size = msec->rawsize ? msec->rawsize : msec->size;
-      if (syms)
-       {
-         *section_buffer
-           = bfd_simple_get_relocated_section_contents (abfd, msec, NULL, syms);
-         if (! *section_buffer)
-           return FALSE;
-       }
-      else
-       {
-         *section_buffer = (bfd_byte *) bfd_malloc (*section_size);
-         if (! *section_buffer)
-           return FALSE;
-         if (! bfd_get_section_contents (abfd, msec, *section_buffer,
-                                         0, *section_size))
-           return FALSE;
-       }
-
-      /* Paranoia - if we are reading in a string section, make sure that it
-        is NUL terminated.  This is to prevent string functions from running
-        off the end of the buffer.  Note - knowing the size of the buffer is
-        not enough as some functions, eg strchr, do not have a range limited
-        equivalent.
-
-        FIXME: We ought to use a flag in the dwarf_debug_sections[] table to
-        determine the nature of a debug section, rather than checking the
-        section name as we do here.  */
-      if (*section_size > 0
-         && (*section_buffer)[*section_size - 1] != 0
-         && (strstr (section_name, "_str") || strstr (section_name, "names")))
+      /* Paranoia - alloc one extra so that we can make sure a string
+        section is NUL terminated.  */
+      contents = (bfd_byte *) bfd_malloc (*section_size + 1);
+      if (contents == NULL)
+       return FALSE;
+      if (syms
+         ? !bfd_simple_get_relocated_section_contents (abfd, msec, contents,
+                                                       syms)
+         : !bfd_get_section_contents (abfd, msec, contents, 0, *section_size))
        {
-         bfd_byte * new_buffer = malloc (*section_size + 1);
-
-         _bfd_error_handler (_("warning: dwarf string section '%s' is not NUL terminated"),
-                             section_name);
-         memcpy (new_buffer, *section_buffer, *section_size);
-         new_buffer[*section_size] = 0;
-         free (*section_buffer);
-         *section_buffer = new_buffer;
+         free (contents);
+         return FALSE;
        }
+      contents[*section_size] = 0;
+      *section_buffer = contents;
     }
 
   /* It is possible to get a bad value for the offset into the section