xdp: fix race on generic receive path

[ Upstream commit bf0bdd1343efbbf65b4d53aef1fce14acbd79d50 ]

Unlike driver mode, generic xdp receive could be triggered
by different threads on different CPU cores at the same time
leading to the fill and rx queue breakage. For example, this
could happen while sending packets from two processes to the
first interface of veth pair while the second part of it is
open with AF_XDP socket.

Need to take a lock for each generic receive to avoid race.

Fixes: c497176cb2e4 ("xsk: add Rx receive functions and poll support")
Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Tested-by: William Tu <u9012063@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index d074b6d60f8af77a355b6755ef3d096237ff55bc..ac3c047d058c95adf361d13224b1cdc319bd8d20 100644 (file)
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h
@@ -67,6 +67,8 @@ struct xdp_sock {
         * in the SKB destructor callback.
         */
        spinlock_t tx_completion_lock;
+       /* Protects generic receive. */
+       spinlock_t rx_lock;
        u64 rx_dropped;
 };
 

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index a14e8864e4fa46ab898e996de3a84bb94b8dc97a..5e0637db92ea42d52a138ec5165802683be73e43 100644 (file)
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -123,13 +123,17 @@ int xsk_generic_rcv(struct xdp_sock *xs, struct xdp_buff *xdp)
        u64 addr;
        int err;
 
-       if (xs->dev != xdp->rxq->dev || xs->queue_id != xdp->rxq->queue_index)
-               return -EINVAL;
+       spin_lock_bh(&xs->rx_lock);
+
+       if (xs->dev != xdp->rxq->dev || xs->queue_id != xdp->rxq->queue_index) {
+               err = -EINVAL;
+               goto out_unlock;
+       }
 
        if (!xskq_peek_addr(xs->umem->fq, &addr) ||
            len > xs->umem->chunk_size_nohr - XDP_PACKET_HEADROOM) {
-               xs->rx_dropped++;
-               return -ENOSPC;
+               err = -ENOSPC;
+               goto out_drop;
        }
 
        addr += xs->umem->headroom;
@@ -138,13 +142,21 @@ int xsk_generic_rcv(struct xdp_sock *xs, struct xdp_buff *xdp)
        memcpy(buffer, xdp->data_meta, len + metalen);
        addr += metalen;
        err = xskq_produce_batch_desc(xs->rx, addr, len);
-       if (!err) {
-               xskq_discard_addr(xs->umem->fq);
-               xsk_flush(xs);
-               return 0;
-       }
+       if (err)
+               goto out_drop;
+
+       xskq_discard_addr(xs->umem->fq);
+       xskq_produce_flush_desc(xs->rx);
 
+       spin_unlock_bh(&xs->rx_lock);
+
+       xs->sk.sk_data_ready(&xs->sk);
+       return 0;
+
+out_drop:
        xs->rx_dropped++;
+out_unlock:
+       spin_unlock_bh(&xs->rx_lock);
        return err;
 }
 
@@ -765,6 +777,7 @@ static int xsk_create(struct net *net, struct socket *sock, int protocol,
 
        xs = xdp_sk(sk);
        mutex_init(&xs->mutex);
+       spin_lock_init(&xs->rx_lock);
        spin_lock_init(&xs->tx_completion_lock);
 
        mutex_lock(&net->xdp.lock);