[PATCH] hso: fix refcnt leak in recent patch.

[NeilBrown <neilb@xxxxxxx>]

Prior to
commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
    hso: fix crash when device disappears while serial port is open

hso_serial_open would always kref_get(&serial->parent->ref) before
returning zero.
Since that commit, it only calls kref_get when returning 0 if
serial->port.count was zero.

This results in calls to
       kref_put(&serial->parent->ref, hso_serial_ref_free);

after hso_serial_ref_free has been called, which dereferences a freed
pointer.

This patch adds the missing kref_get().

Fixes: commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b
Cc: stable@xxxxxxxxxxxxxxx (v4.0)
Cc: Olivier Sobrie <olivier@xxxxxxxxx>
Signed-off-by: NeilBrown <neilb@xxxxxxx>

diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index 75befc1bd816..6848fc903340 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -1299,6 +1299,7 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
 		}
 	} else {
 		D1("Port was already open");
+		kref_get(&serial->parent->ref);
 	}
 
 	usb_autopm_put_interface(serial->parent->interface);

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