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@mellanox.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Björn Töpel <bjorn.topel@intel.com>
Link: https://lore.kernel.org/bpf/20210118160333.333439-1-maximmi@mellanox.com

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 8037b04..4a83117 100644 (file)
--- 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;
 }