From: Xin Long <lucien.xin@gmail.com>
Date: Sun, 19 Nov 2017 11:31:04 +0000 (+0800)
Subject: tun: fix rcu_read_lock imbalance in tun_build_skb
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=29d631e5941366ee5eb50b3b592ca99186115a63;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

tun: fix rcu_read_lock imbalance in tun_build_skb


[ Upstream commit 654d573845f35017dc397840fa03610fef3d08b0 ]

rcu_read_lock in tun_build_skb is used to rcu_dereference tun->xdp_prog
safely, rcu_read_unlock should be done in every return path.

Now I could see one place missing it, where it returns NULL in switch-case
XDP_REDIRECT,  another palce using rcu_read_lock wrongly, where it returns
NULL in if (xdp_xmit) chunk.

So fix both in this patch.

Fixes: 761876c857cb ("tap: XDP support")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index a5c47db94846..d06f88312e1e 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1326,6 +1326,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
 			err = xdp_do_redirect(tun->dev, &xdp, xdp_prog);
 			if (err)
 				goto err_redirect;
+			rcu_read_unlock();
 			return NULL;
 		case XDP_TX:
 			xdp_xmit = true;
@@ -1358,7 +1359,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
 	if (xdp_xmit) {
 		skb->dev = tun->dev;
 		generic_xdp_tx(skb, xdp_prog);
-		rcu_read_lock();
+		rcu_read_unlock();
 		return NULL;
 	}