linux-kernel - [PATCH] ttyprintk: Fix NULL pointer deref by setting tty

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Message-ID: <20130510224013.GA5706@blackbox.djwong.org>
Date:	Fri, 10 May 2013 15:40:13 -0700
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	Jiri Slaby <jslaby@...e.cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Arnd Bergmann <arnd@...db.de>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH] ttyprintk: Fix NULL pointer deref by setting tty_port ops
 after initializing port

tty_port_init() zeroes out the tty port, which means that we have to set the
ops pointer /after/, not before this call.  Otherwise, tty_port_open will crash
when it tries to deref ops, which is now a NULL pointer.

Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
 drivers/char/ttyprintk.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/ttyprintk.c b/drivers/char/ttyprintk.c
index 4945bd3..d5d2e4a 100644
--- a/drivers/char/ttyprintk.c
+++ b/drivers/char/ttyprintk.c
@@ -179,7 +179,6 @@ static int __init ttyprintk_init(void)
 {
 	int ret = -ENOMEM;
 
-	tpk_port.port.ops = &null_ops;
 	mutex_init(&tpk_port.port_write_mutex);
 
 	ttyprintk_driver = tty_alloc_driver(1,
@@ -190,6 +189,7 @@ static int __init ttyprintk_init(void)
 		return PTR_ERR(ttyprintk_driver);
 
 	tty_port_init(&tpk_port.port);
+	tpk_port.port.ops = &null_ops;
 
 	ttyprintk_driver->driver_name = "ttyprintk";
 	ttyprintk_driver->name = "ttyprintk";
--
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