linux-kernel - [PATCH] tty_port: Fix refcounting leak in tty_port_tty

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Message-Id: <1374729977-7164-1-git-send-email-gianluca@sottospazio.it>
Date:	Thu, 25 Jul 2013 07:26:16 +0200
From:	Gianluca Anzolin <gianluca@...tospazio.it>
To:	gregkh@...uxfoundation.org
Cc:	jslaby@...e.cz, gustavo@...ovan.org, peter@...leysoftware.com,
	linux-kernel@...r.kernel.org,
	Gianluca Anzolin <gianluca@...tospazio.it>
Subject: [PATCH] tty_port: Fix refcounting leak in tty_port_tty_hangup()

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@...labora.co.uk>
Signed-off-by: Gianluca Anzolin <gianluca@...tospazio.it>
---
 drivers/tty/tty_port.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index 121aeb9..f597e88 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -256,10 +256,9 @@ void tty_port_tty_hangup(struct tty_port *port, bool check_clocal)
 {
 	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);
 
-- 
1.8.3.3

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