tty: handle NULL parameters in free_tty_struct()

We sometimes pass NULL pointers to free_tty_struct().  One example where
it can happen is in the error handling code in pty_common_install().

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 608749978df4..6784aae210e3 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -181,6 +181,8 @@ struct tty_struct *alloc_tty_struct(void)
 
 void free_tty_struct(struct tty_struct *tty)
 {
+        if (!tty)
+                return;
         if (tty->dev)
                 put_device(tty->dev);
         kfree(tty->write_buf);