[PATCH] Potential null pointer dereference in amiga serial driver

A pointer is dereferenced before it is null-checked.
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

drivers/char/amiserial.c

@@ -861,13 +861,18 @@ static void change_speed(struct async_struct *info,
 
 static void rs_put_char(struct tty_struct *tty, unsigned char ch)
 {
-	struct async_struct *info = (struct async_struct *)tty->driver_data;
+	struct async_struct *info;
 	unsigned long flags;
 
+	if (!tty)
+		return;
+
+	info = tty->driver_data;
+
 	if (serial_paranoia_check(info, tty->name, "rs_put_char"))
 		return;
 
-	if (!tty || !info->xmit.buf)
+	if (!info->xmit.buf)
 		return;
 
 	local_irq_save(flags);
@@ -910,13 +915,18 @@ static void rs_flush_chars(struct tty_struct *tty)
 static int rs_write(struct tty_struct * tty, const unsigned char *buf, int count)
 {
 	int	c, ret = 0;
-	struct async_struct *info = (struct async_struct *)tty->driver_data;
+	struct async_struct *info;
 	unsigned long flags;
 
+	if (!tty)
+		return 0;
+
+	info = tty->driver_data;
+
 	if (serial_paranoia_check(info, tty->name, "rs_write"))
 		return 0;
 
-	if (!tty || !info->xmit.buf || !tmp_buf)
+	if (!info->xmit.buf || !tmp_buf)
 		return 0;
 
 	local_save_flags(flags);