netdev - [PATCH net-next v2 2/2] netdev: Enforce index cap in netdev_get_tx

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Message-Id: <20230321150725.127229-2-nnac123@linux.ibm.com>
Date:   Tue, 21 Mar 2023 10:07:25 -0500
From:   Nick Child <nnac123@...ux.ibm.com>
To:     netdev@...r.kernel.org
Cc:     Nick Child <nnac123@...ux.ibm.com>
Subject: [PATCH net-next v2 2/2] netdev: Enforce index cap in netdev_get_tx_queue

When requesting a TX queue at a given index, warn on out-of-bounds
referencing if the index is greater than the allocated number of
queues.

Specifically, since this function is used heavily in the networking
stack use DEBUG_NET_WARN_ON_ONCE to avoid executing a new branch on
every packet.

Signed-off-by: Nick Child <nnac123@...ux.ibm.com>
---
Changes since v1 (respond to Jakubs review):
 - send to net-next instead of net
 - use DEBUG_NET_WARN_ON_ONCE instead of a conditonal returning 1st queue

v1 - https://lore.kernel.org/netdev/20230320214942.38395e6e@kicinski-fedora-PC1C0HJN/

 include/linux/netdevice.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 23b0d7eaaadd..838b7310a80b 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2482,6 +2482,7 @@ static inline
 struct netdev_queue *netdev_get_tx_queue(const struct net_device *dev,
 					 unsigned int index)
 {
+	DEBUG_NET_WARN_ON_ONCE(index >= dev->num_tx_queues);
 	return &dev->_tx[index];
 }
 
-- 
2.31.1