[patch] Fix crash in read_pe_exported_syms

[Corinna Vinschen <vinschen@redhat.com>]

Hi,

when running GDB from current CVS on a PE/COFF target, and if this
target has no debug symbols, nor any exported symbols, then GDB crashes
with a SEGV in the first do_cleanup called from coff_symfile_read.

The reason is that read_pe_exported_syms creates two cleanup handlers,
one of them referring to a symbol on the local stack:

  struct read_pe_section_data *section_data;
  [...]
  section_data = xzalloc (...)
  make_cleanup (free_current_contents, &section_data);

but then returns from the function early in three different scenarios
without calling do_cleanup.  The subsequent do_cleanup call in
coff_symfile_read now tries to dereference from an invalid stack address
and ultimately crashes.

Below is a patch.  Ok to apply?


Thanks,
Corinna


	* coff-pe-read.c (read_pe_exported_syms): Don't return without
	calling do_cleanup.


Index: coff-pe-read.c
===================================================================
RCS file: /cvs/src/src/gdb/coff-pe-read.c,v
retrieving revision 1.23
diff -u -p -r1.23 coff-pe-read.c
--- coff-pe-read.c	1 Jan 2013 06:32:40 -0000	1.23
+++ coff-pe-read.c	2 Mar 2013 11:00:42 -0000
@@ -379,7 +379,7 @@ read_pe_exported_syms (struct objfile *o
       /* This is not a recognized PE format file.  Abort now, because
 	 the code is untested on anything else.  *FIXME* test on
 	 further architectures and loosen or remove this test.  */
-      return;
+      goto cleanup;
     }
 
   /* Get pe_header, optional header and numbers of export entries.  */
@@ -392,7 +392,7 @@ read_pe_exported_syms (struct objfile *o
 
   if (num_entries < 1)		/* No exports.  */
     {
-      return;
+      goto cleanup;
     }
   if (is_pe64)
     {
@@ -448,7 +448,7 @@ read_pe_exported_syms (struct objfile *o
   if (export_size == 0)
     {
       /* Empty export table.  */
-      return;
+      goto cleanup;
     }
 
   /* Scan sections and store the base and size of the relevant
@@ -614,6 +614,7 @@ read_pe_exported_syms (struct objfile *o
     fprintf_unfiltered (gdb_stdlog, _("Finished reading \"%s\", exports %ld,"
 			" forwards %ld, total %ld/%ld.\n"), dll_name, nbnormal,
 			nbforward, nbnormal + nbforward, nexp);
+cleanup:
   /* Discard expdata and section_data.  */
   do_cleanups (back_to);
 }

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat