2012-03-02 Kees Cook <keescook@chromium.org>

        [BZ #13656]
        * stdio-common/vfprintf.c (vfprintf): Check for nargs overflow and
        possibly allocate from heap instead of stack.
        * stdio-common/bug-vfprintf-nargs.c: New file.
        * stdio-common/Makefile (tests): Add nargs overflow test.

1 files changed, 78 insertions, 0 deletions

diff --git a/stdio-common/bug-vfprintf-nargs.c b/stdio-common/bug-vfprintf-nargs.c
new file mode 100644
index 0000000..13c66c0
--- /dev/null
+++ b/stdio-common/bug-vfprintf-nargs.c
@@ -0,0 +1,78 @@
+/* Test for vfprintf nargs allocation overflow (BZ #13656).
+   Copyright (C) 2012 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Kees Cook <keescook@chromium.org>, 2012.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <inttypes.h>
+#include <string.h>
+#include <signal.h>
+
+static int
+format_failed (const char *fmt, const char *expected)
+{
+  char output[80];
+
+  printf ("%s : ", fmt);
+
+  memset (output, 0, sizeof output);
+  /* Having sprintf itself detect a failure is good.  */
+  if (sprintf (output, fmt, 1, 2, 3, "test") > 0
+      && strcmp (output, expected) != 0)
+    {
+      printf ("FAIL (output '%s' != expected '%s')\n", output, expected);
+      return 1;
+    }
+  puts ("ok");
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  int rc = 0;
+  char buf[64];
+
+  /* Regular positionals work.  */
+  if (format_failed ("%1$d", "1") != 0)
+    rc = 1;
+
+  /* Regular width positionals work.  */
+  if (format_failed ("%1$*2$d", " 1") != 0)
+    rc = 1;
+
+  /* Positional arguments are constructed via read_int, so nargs can only
+     overflow on 32-bit systems.  On 64-bit systems, it will attempt to
+     allocate a giant amount of memory and possibly crash, which is the
+     expected situation.  Since the 64-bit behavior is arch-specific, only
+     test this on 32-bit systems.  */
+  if (sizeof (long int) == 4)
+    {
+      sprintf (buf, "%%1$d %%%" PRIdPTR "$d", UINT32_MAX / sizeof (int));
+      if (format_failed (buf, "1 %$d") != 0)
+        rc = 1;
+    }
+
+  return rc;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"