score: do_sigaltstack() expects a userland pointer...

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

arch/score/kernel/signal.c

@@ -148,7 +148,6 @@ score_rt_sigreturn(struct pt_regs *regs)
 {
 	struct rt_sigframe __user *frame;
 	sigset_t set;
-	stack_t st;
 	int sig;
 
 	/* Always make any pending restarted system calls return -EINTR */
@@ -168,12 +167,10 @@ score_rt_sigreturn(struct pt_regs *regs)
 	else if (sig)
 		force_sig(sig, current);
 
-	if (__copy_from_user(&st, &frame->rs_uc.uc_stack, sizeof(st)))
-		goto badframe;
-
 	/* It is more difficult to avoid calling this function than to
 	   call it and ignore errors.  */
-	do_sigaltstack((stack_t __user *)&st, NULL, regs->regs[0]);
+	if (do_sigaltstack(&frame->rs_uc.uc_stack, NULL, regs->regs[0]) == -EFAULT)
+		goto badframe;
 	regs->is_syscall = 0;
 
 	__asm__ __volatile__(