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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Dmitry Vyukov <dvyukov@google.com>,
        Jason Wang <jasowang@redhat.com>,
        Cong Wang <xiyou.wangcong@gmail.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.14 47/71] tun: fix a memory leak for tfile->tx_array
Date:   Mon, 29 Jan 2018 13:57:15 +0100
Message-Id: <20180129123830.359300819@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Cong Wang <xiyou.wangcong@gmail.com>


[ Upstream commit 4df0bfc79904b7169dc77dcce44598b1545721f9 ]

tfile->tun could be detached before we close the tun fd,
via tun_detach_all(), so it should not be used to check for
tfile->tx_array.

As Jason suggested, we probably have to clean it up
unconditionally both in __tun_deatch() and tun_detach_all(),
but this requires to check if it is initialized or not.
Currently skb_array_cleanup() doesn't have such a check,
so I check it in the caller and introduce a helper function,
it is a bit ugly but we can always improve it in net-next.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Fixes: 1576d9860599 ("tun: switch to use skb array for tx")
Cc: Jason Wang <jasowang@redhat.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/tun.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -534,6 +534,14 @@ static void tun_queue_purge(struct tun_f
 	skb_queue_purge(&tfile->sk.sk_error_queue);
 }
 
+static void tun_cleanup_tx_array(struct tun_file *tfile)
+{
+	if (tfile->tx_array.ring.queue) {
+		skb_array_cleanup(&tfile->tx_array);
+		memset(&tfile->tx_array, 0, sizeof(tfile->tx_array));
+	}
+}
+
 static void __tun_detach(struct tun_file *tfile, bool clean)
 {
 	struct tun_file *ntfile;
@@ -575,8 +583,7 @@ static void __tun_detach(struct tun_file
 			    tun->dev->reg_state == NETREG_REGISTERED)
 				unregister_netdevice(tun->dev);
 		}
-		if (tun)
-			skb_array_cleanup(&tfile->tx_array);
+		tun_cleanup_tx_array(tfile);
 		sock_put(&tfile->sk);
 	}
 }
@@ -616,11 +623,13 @@ static void tun_detach_all(struct net_de
 		/* Drop read queue */
 		tun_queue_purge(tfile);
 		sock_put(&tfile->sk);
+		tun_cleanup_tx_array(tfile);
 	}
 	list_for_each_entry_safe(tfile, tmp, &tun->disabled, next) {
 		tun_enable_queue(tfile);
 		tun_queue_purge(tfile);
 		sock_put(&tfile->sk);
+		tun_cleanup_tx_array(tfile);
 	}
 	BUG_ON(tun->numdisabled != 0);
 
@@ -2624,6 +2633,8 @@ static int tun_chr_open(struct inode *in
 
 	sock_set_flag(&tfile->sk, SOCK_ZEROCOPY);
 
+	memset(&tfile->tx_array, 0, sizeof(tfile->tx_array));
+
 	return 0;
 }