linux-kernel - [PATCH] net: caif: fix memory leak in ldisc

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Date:   Sat, 12 Jun 2021 17:51:22 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     davem@...emloft.net, kuba@...nel.org, gregkh@...uxfoundation.org
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pavel Skripkin <paskripkin@...il.com>,
        syzbot+f303e045423e617d2cad@...kaller.appspotmail.com
Subject: [PATCH] net: caif: fix memory leak in ldisc_open

Syzbot reported memory leak in tty_init_dev().
The problem was in unputted tty in ldisc_open()

static int ldisc_open(struct tty_struct *tty)
{
...
	ser->tty = tty_kref_get(tty);
...
	result = register_netdevice(dev);
	if (result) {
		rtnl_unlock();
		free_netdev(dev);
		return -ENODEV;
	}
...
}

Ser pointer is netdev private_data, so after free_netdev()
this pointer goes away with unputted tty reference. So, fix
it by adding tty_kref_put() before freeing netdev.

Reported-and-tested-by: syzbot+f303e045423e617d2cad@...kaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
---
 drivers/net/caif/caif_serial.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/caif/caif_serial.c b/drivers/net/caif/caif_serial.c
index d17482395a4d..4ffbfd534f18 100644
--- a/drivers/net/caif/caif_serial.c
+++ b/drivers/net/caif/caif_serial.c
@@ -350,6 +350,7 @@ static int ldisc_open(struct tty_struct *tty)
 	rtnl_lock();
 	result = register_netdevice(dev);
 	if (result) {
+		tty_kref_put(tty);
 		rtnl_unlock();
 		free_netdev(dev);
 		return -ENODEV;
-- 
2.32.0