[Patch net v2] tun: fix a memory leak for tfile->tx_array

[Cong Wang <xiyou.wangcong@gmail.com>]

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, 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, it is 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>
---
 drivers/net/tun.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 4f4a842a1c9c..4c85474ffbaf 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -657,7 +657,7 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
 			    tun->dev->reg_state == NETREG_REGISTERED)
 				unregister_netdevice(tun->dev);
 		}
-		if (tun)
+		if (tfile->tx_array.ring.queue)
 			skb_array_cleanup(&tfile->tx_array);
 		sock_put(&tfile->sk);
 	}
@@ -2851,6 +2851,8 @@ static int tun_chr_open(struct inode *inode, struct file * file)
 
 	sock_set_flag(&tfile->sk, SOCK_ZEROCOPY);
 
+	memset(&tfile->tx_array, 0, sizeof(tfile->tx_array));
+
 	return 0;
 }
 
-- 
2.13.0