[PATCH 3/3] tst-longjmp_chk3: new test for checking sigaltstack edge cases

[Mike Frysinger <vapier at gentoo dot org>]

Make sure the longjmp checking logic catches stacks that are slightly
outside of a valid alternative signal stack.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

2013-12-29   Mike Frysinger  <vapier@gentoo.org>

	* debug/Makefile (CFLAGS-tst-longjmp_chk3.c): Define.
	(CPPFLAGS-tst-longjmp_chk3.c): Likewise.
	* debug/tst-longjmp_chk3.c: New file.
---
 debug/Makefile           |  2 ++
 debug/tst-longjmp_chk3.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 87 insertions(+)
 create mode 100644 debug/tst-longjmp_chk3.c

diff --git a/debug/Makefile b/debug/Makefile
index 13ee5c8..5bfc75f 100644
--- a/debug/Makefile
+++ b/debug/Makefile
@@ -90,6 +90,8 @@ CFLAGS-tst-longjmp_chk.c = -fexceptions -fasynchronous-unwind-tables
 CPPFLAGS-tst-longjmp_chk.c = -D_FORTIFY_SOURCE=1
 CFLAGS-tst-longjmp_chk2.c = -fexceptions -fasynchronous-unwind-tables
 CPPFLAGS-tst-longjmp_chk2.c = -D_FORTIFY_SOURCE=1
+CFLAGS-tst-longjmp_chk3.c = -fexceptions -fasynchronous-unwind-tables
+CPPFLAGS-tst-longjmp_chk3.c = -D_FORTIFY_SOURCE=1
 
 # We know these tests have problems with format strings, this is what
 # we are testing.  Disable that warning.
diff --git a/debug/tst-longjmp_chk3.c b/debug/tst-longjmp_chk3.c
new file mode 100644
index 0000000..5b814ae
--- /dev/null
+++ b/debug/tst-longjmp_chk3.c
@@ -0,0 +1,85 @@
+/* Make sure longjmp fortification catches bad signal stacks.
+   Copyright (C) 2013 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <setjmp.h>
+#include <signal.h>
+#include <string.h>
+
+static int do_test (void);
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
+
+static char buf[SIGSTKSZ * 4];
+static jmp_buf jb;
+
+static void
+handler (int sig)
+{
+  if (sig == SIGUSR1)
+    {
+      if (setjmp (jb) != 0)
+	{
+	  puts ("setjmp should not have been called");
+	  kill (getpid (), SIGTERM);
+	}
+    }
+  else if (sig == SIGABRT)
+    {
+      /* Yeah it worked.  */
+      _exit (0);
+    }
+}
+
+static int
+do_test (void)
+{
+  stack_t ss;
+
+  set_fortify_handler (handler);
+
+  /* Create a valid signal stack and enable it.  */
+  ss.ss_sp = buf;
+  ss.ss_size = sizeof (buf);
+  ss.ss_flags = 0;
+  if (sigaltstack (&ss, NULL) < 0)
+    {
+      printf ("first sigaltstack failed: %m\n");
+      return 1;
+    }
+
+  /* Trigger the signal handler which will create a jmpbuf that points to the
+     end of the signal stack.  */
+  signal (SIGUSR1, handler);
+  kill (getpid (), SIGUSR1);
+
+  /* Shrink the signal stack so the jmpbuf is now invalid.
+     We adjust the start & end to handle stacks that grow up & down.  */
+  ss.ss_sp = buf + sizeof (buf) / 2;
+  ss.ss_size = sizeof (buf) / 4;
+  if (sigaltstack (&ss, NULL) < 0)
+    {
+      printf ("second sigaltstack failed: %m\n");
+      return 1;
+    }
+
+  /* This should fail.  */
+  longjmp (jb, 1);
+
+  puts ("longjmp returned and shouldn't");
+  return 1;
+}
-- 
1.8.4.3