netdev - [PATCH bpf] xsk: Clear pool even for inactive queues

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Message-Id: <20210118160333.333439-1-maximmi@mellanox.com>
Date:   Mon, 18 Jan 2021 18:03:33 +0200
From:   Maxim Mikityanskiy <maximmi@...lanox.com>
To:     Magnus Karlsson <magnus.karlsson@...el.com>,
        Björn Töpel <bjorn.topel@...el.com>
Cc:     Jonathan Lemon <jonathan.lemon@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH bpf] xsk: Clear pool even for inactive queues

The number of queues can change by other means, rather than ethtool. For
example, attaching an mqprio qdisc with num_tc > 1 leads to creating
multiple sets of TX queues, which may be then destroyed when mqprio is
deleted. If an AF_XDP socket is created while mqprio is active,
dev->_tx[queue_id].pool will be filled, but then real_num_tx_queues may
decrease with deletion of mqprio, which will mean that the pool won't be
NULLed, and a further increase of the number of TX queues may expose a
dangling pointer.

To avoid any potential misbehavior, this commit clears pool for RX and
TX queues, regardless of real_num_*_queues, still taking into
consideration num_*_queues to avoid overflows.

Fixes: 1c1efc2af158 ("xsk: Create and free buffer pool independently from umem")
Fixes: a41b4f3c58dd ("xsk: simplify xdp_clear_umem_at_qid implementation")
Signed-off-by: Maxim Mikityanskiy <maximmi@...lanox.com>
---
 net/xdp/xsk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 8037b04a9edd..4a83117507f5 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -108,9 +108,9 @@ EXPORT_SYMBOL(xsk_get_pool_from_qid);

 void xsk_clear_pool_at_qid(struct net_device *dev, u16 queue_id)
 {
-	if (queue_id < dev->real_num_rx_queues)
+	if (queue_id < dev->num_rx_queues)
 		dev->_rx[queue_id].pool = NULL;
-	if (queue_id < dev->real_num_tx_queues)
+	if (queue_id < dev->num_tx_queues)
 		dev->_tx[queue_id].pool = NULL;
 }

-- 
2.25.1