Hexagon: check to if we will overflow the signal stack

Signed-off-by: Richard Kuo <rkuo@codeaurora.org>

arch/hexagon/kernel/signal.c

@@ -41,6 +41,10 @@ static void __user *get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
 {
 	unsigned long sp = regs->r29;
 
+	/* check if we would overflow the alt stack */
+	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size)))
+		return (void __user __force *)-1UL;
+
 	/* Switch to signal stack if appropriate */
 	if ((ka->sa.sa_flags & SA_ONSTACK) && (sas_ss_flags(sp) == 0))
 		sp = current->sas_ss_sp + current->sas_ss_size;