n_tty: Fix auditing support for cannonical mode

commit 72586c60 upstream.

Commit 32f13521
("n_tty: Line copy to user buffer in canonical mode")
changed cannonical mode copying to use copy_to_user
but missed adding the call to the audit framework.
Add in the appropriate functions to get audit support.

Fixes: 32f13521 ("n_tty: Line copy to user buffer in canonical mode")
Reported-by: Miloslav Trmač <mitr@redhat.com>
Signed-off-by: Laura Abbott <labbott@fedoraproject.org>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/tty/n_tty.c

@@ -160,6 +160,17 @@ static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
 	return put_user(x, ptr);
 }
 
+static inline int tty_copy_to_user(struct tty_struct *tty,
+					void __user *to,
+					const void *from,
+					unsigned long n)
+{
+	struct n_tty_data *ldata = tty->disc_data;
+
+	tty_audit_add_data(tty, to, n, ldata->icanon);
+	return copy_to_user(to, from, n);
+}
+
 static int receive_room(struct tty_struct *tty)
 {
 	struct n_tty_data *ldata = tty->disc_data;
@@ -2064,12 +2075,12 @@ static int canon_copy_from_read_buf(struct tty_struct *tty,
 		    __func__, eol, found, n, c, size, more);
 
 	if (n > size) {
-		ret = copy_to_user(*b, read_buf_addr(ldata, tail), size);
+		ret = tty_copy_to_user(tty, *b, read_buf_addr(ldata, tail), size);
 		if (ret)
 			return -EFAULT;
-		ret = copy_to_user(*b + size, ldata->read_buf, n - size);
+		ret = tty_copy_to_user(tty, *b + size, ldata->read_buf, n - size);
 	} else
-		ret = copy_to_user(*b, read_buf_addr(ldata, tail), n);
+		ret = tty_copy_to_user(tty, *b, read_buf_addr(ldata, tail), n);
 
 	if (ret)
 		return -EFAULT;