diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index a9d256d6e909c1aecfc854732694d608256aeb15..6e1f1505f04e4b0ae948dfad4be3319df1debdb7 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -210,6 +210,9 @@ static int pty_signal(struct tty_struct *tty, int sig)
 {
 	struct pid *pgrp;
 
+	if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
+		return -EINVAL;
+
 	if (tty->link) {
 		pgrp = tty_get_pgrp(tty->link);
 		if (pgrp)