From: Maxim Mikityanskiy maximmi@mellanox.com
[ Upstream commit 06870682087b58398671e8cdc896cd62314c4399 ]
The XSK wakeup callback in drivers makes some sanity checks before triggering NAPI. However, some configuration changes may occur during this function that affect the result of those checks. For example, the interface can go down, and all the resources will be destroyed after the checks in the wakeup function, but before it attempts to use these resources. Wrap this callback in rcu_read_lock to allow driver to synchronize_rcu before actually destroying the resources.
xsk_wakeup is a new function that encapsulates calling ndo_xsk_wakeup wrapped into the RCU lock. After this commit, xsk_poll starts using xsk_wakeup and checks xs->zc instead of ndo_xsk_wakeup != NULL to decide ndo_xsk_wakeup should be called. It also fixes a bug introduced with the need_wakeup feature: a non-zero-copy socket may be used with a driver supporting zero-copy, and in this case ndo_xsk_wakeup should not be called, so the xs->zc check is the correct one.
Fixes: 77cd0d7b3f25 ("xsk: add support for need_wakeup flag in AF_XDP rings") Signed-off-by: Maxim Mikityanskiy maximmi@mellanox.com Signed-off-by: Björn Töpel bjorn.topel@intel.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/20191217162023.16011-2-maximmi@mellanox.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/xdp/xsk.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-)
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index 9044073fbf22..d426fc01c529 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -305,12 +305,21 @@ bool xsk_umem_consume_tx(struct xdp_umem *umem, struct xdp_desc *desc) } EXPORT_SYMBOL(xsk_umem_consume_tx);
-static int xsk_zc_xmit(struct xdp_sock *xs) +static int xsk_wakeup(struct xdp_sock *xs, u8 flags) { struct net_device *dev = xs->dev; + int err; + + rcu_read_lock(); + err = dev->netdev_ops->ndo_xsk_wakeup(dev, xs->queue_id, flags); + rcu_read_unlock(); + + return err; +}
- return dev->netdev_ops->ndo_xsk_wakeup(dev, xs->queue_id, - XDP_WAKEUP_TX); +static int xsk_zc_xmit(struct xdp_sock *xs) +{ + return xsk_wakeup(xs, XDP_WAKEUP_TX); }
static void xsk_destruct_skb(struct sk_buff *skb) @@ -424,19 +433,16 @@ static unsigned int xsk_poll(struct file *file, struct socket *sock, unsigned int mask = datagram_poll(file, sock, wait); struct sock *sk = sock->sk; struct xdp_sock *xs = xdp_sk(sk); - struct net_device *dev; struct xdp_umem *umem;
if (unlikely(!xsk_is_bound(xs))) return mask;
- dev = xs->dev; umem = xs->umem;
if (umem->need_wakeup) { - if (dev->netdev_ops->ndo_xsk_wakeup) - dev->netdev_ops->ndo_xsk_wakeup(dev, xs->queue_id, - umem->need_wakeup); + if (xs->zc) + xsk_wakeup(xs, umem->need_wakeup); else /* Poll needs to drive Tx also in copy mode */ __xsk_sendmsg(sk);