[PATCH net 2/2] netdev: Enforce index cap in netdev_get_tx_queue

[Nick Child <nnac123@linux.ibm.com>]

When requesting a TX queue at a given index, prevent out-of-bounds
referencing by ensuring that the index is within the allocated number
of queues.

If there is an out-of-bounds reference then inform the user and return
a reference to the first tx queue instead.

Fixes: e8a0464cc950 ("netdev: Allocate multiple queues for TX.")
Signed-off-by: Nick Child <nnac123@linux.ibm.com>
---
 include/linux/netdevice.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 23b0d7eaaadd..fe88b1a7393d 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2482,6 +2482,13 @@ static inline
 struct netdev_queue *netdev_get_tx_queue(const struct net_device *dev,
 					 unsigned int index)
 {
+	if (unlikely(index >= dev->num_tx_queues)) {
+		net_warn_ratelimited("%s selects TX queue %d, but number of TX queues is %d\n",
+				     dev->name, index,
+				     dev->num_tx_queues);
+		return &dev->_tx[0];
+	}
+
 	return &dev->_tx[index];
 }
 
-- 
2.31.1