xtensa: don't mask signals if we fail to setup signal stack

setup_frame() needs to return an indication of whether it succeeded or
failed in setting up the signal stack frame.  If setup_frame() fails then
we must not modify current->blocked.
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/xtensa/kernel/signal.c

@@ -336,7 +336,7 @@ gen_return_code(unsigned char *codemem)
 }
 
 
-static void setup_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
+static int setup_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 		       sigset_t *set, struct pt_regs *regs)
 {
 	struct rt_sigframe *frame;
@@ -422,10 +422,11 @@ static void setup_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 		current->comm, current->pid, signal, frame, regs->pc);
 #endif
 
-	return;
+	return 0;
 
 give_sigsegv:
 	force_sigsegv(sig, current);
+	return -EFAULT;
 }
 
 /*
@@ -534,7 +535,9 @@ int do_signal(struct pt_regs *regs, sigset_t *oldset)
 
 		/* Whee!  Actually deliver the signal.  */
 		/* Set up the stack frame */
-		setup_frame(signr, &ka, &info, oldset, regs);
+		ret = setup_frame(signr, &ka, &info, oldset, regs);
+		if (ret)
+			return ret;
 
 		spin_lock_irq(&current->sighand->siglock);
 		sigorsets(&current->blocked, &current->blocked, &ka.sa.sa_mask);