[ 91/99] tty_port: Fix refcounting leak in tty_port_tty_hangup()

[Greg Kroah-Hartman]

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Gianluca Anzolin <gianluca@xxxxxxxxxxxxxx>

commit 1d9e689c934bd5ecb0f273c6c65e0655c5cfee5f upstream.

The function tty_port_tty_hangup() could leak a reference to the tty_struct:

        struct tty_struct *tty = tty_port_tty_get(port);

        if (tty && (!check_clocal || !C_CLOCAL(tty))) {
                tty_hangup(tty);
                tty_kref_put(tty);
        }

If tty != NULL and the second condition is false we never call tty_kref_put and
the reference is leaked.

Fix by always calling tty_kref_put() which accepts a NULL argument.

The patch fixes a regression introduced by commit aa27a094.

Acked-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
Signed-off-by: Gianluca Anzolin <gianluca@xxxxxxxxxxxxxx>
Acked-by: Jiri Slaby <jslaby@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/tty/tty_port.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -256,10 +256,9 @@ void tty_port_tty_hangup(struct tty_port
 {
 	struct tty_struct *tty = tty_port_tty_get(port);
 
-	if (tty && (!check_clocal || !C_CLOCAL(tty))) {
+	if (tty && (!check_clocal || !C_CLOCAL(tty)))
 		tty_hangup(tty);
-		tty_kref_put(tty);
-	}
+	tty_kref_put(tty);
 }
 EXPORT_SYMBOL_GPL(tty_port_tty_hangup);
 


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