Merge branch 'waitid-fix'

Merge waitid() fix from Kees Cook.

I'd have hoped that the unsafe_{get|put}_user() naming would have
avoided these kinds of stupid bugs, but no such luck.

* waitid-fix:
  waitid(): Add missing access_ok() checks
diff --git a/kernel/exit.c b/kernel/exit.c
index f2cd53e..cf28528 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1610,6 +1610,9 @@
 	if (!infop)
 		return err;
 
+	if (!access_ok(VERIFY_WRITE, infop, sizeof(*infop)))
+		goto Efault;
+
 	user_access_begin();
 	unsafe_put_user(signo, &infop->si_signo, Efault);
 	unsafe_put_user(0, &infop->si_errno, Efault);
@@ -1735,6 +1738,9 @@
 	if (!infop)
 		return err;
 
+	if (!access_ok(VERIFY_WRITE, infop, sizeof(*infop)))
+		goto Efault;
+
 	user_access_begin();
 	unsafe_put_user(signo, &infop->si_signo, Efault);
 	unsafe_put_user(0, &infop->si_errno, Efault);