This is a note to let you know that I've just added the patch titled

tun: fix rcu_read_lock imbalance in tun_build_skb

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: tun-fix-rcu_read_lock-imbalance-in-tun_build_skb.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Thu Dec 14 11:45:40 CET 2017

From: Xin Long lucien.xin@gmail.com Date: Sun, 19 Nov 2017 19:31:04 +0800 Subject: tun: fix rcu_read_lock imbalance in tun_build_skb

From: Xin Long lucien.xin@gmail.com

[ 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 --- drivers/net/tun.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1326,6 +1326,7 @@ static struct sk_buff *tun_build_skb(str 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(str if (xdp_xmit) { skb->dev = tun->dev; generic_xdp_tx(skb, xdp_prog); - rcu_read_lock(); + rcu_read_unlock(); return NULL; }

Patches currently in stable-queue which might be from lucien.xin@gmail.com are

queue-4.14/sctp-use-right-member-as-the-param-of-list_for_each_entry.patch queue-4.14/tun-fix-rcu_read_lock-imbalance-in-tun_build_skb.patch