netdev - [PATCH net-next 2/2] net/dpaa2: Avoid explicit cpumask var allocation on stack

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Message-Id: <20240329105610.922675-3-dawei.li@shingroup.cn>
Date: Fri, 29 Mar 2024 18:56:10 +0800
From: Dawei Li <dawei.li@...ngroup.cn>
To: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	ioana.ciornei@....com,
	wintera@...ux.ibm.com,
	twinkler@...ux.ibm.com
Cc: netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-s390@...r.kernel.org,
	Dawei Li <dawei.li@...ngroup.cn>
Subject: [PATCH net-next 2/2] net/dpaa2: Avoid explicit cpumask var allocation on stack

For CONFIG_CPUMASK_OFFSTACK=y kernel, explicit allocation of cpumask
variable on stack is not recommended since it can cause potential stack
overflow.

Instead, kernel code should always use *cpumask_var API(s) to allocate
cpumask var in config-neutral way, leaving allocation strategy to
CONFIG_CPUMASK_OFFSTACK.

Use *cpumask_var API(s) to address it.

Signed-off-by: Dawei Li <dawei.li@...ngroup.cn>
---
 drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
index 888509cf1f21..40e881829595 100644
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
@@ -2896,11 +2896,14 @@ static int dpaa2_eth_xdp_xmit(struct net_device *net_dev, int n,
 static int update_xps(struct dpaa2_eth_priv *priv)
 {
 	struct net_device *net_dev = priv->net_dev;
-	struct cpumask xps_mask;
-	struct dpaa2_eth_fq *fq;
 	int i, num_queues, netdev_queues;
+	struct dpaa2_eth_fq *fq;
+	cpumask_var_t xps_mask;
 	int err = 0;
 
+	if (!alloc_cpumask_var(&xps_mask, GFP_KERNEL))
+		return -ENOMEM;
+
 	num_queues = dpaa2_eth_queue_count(priv);
 	netdev_queues = (net_dev->num_tc ? : 1) * num_queues;
 
@@ -2910,16 +2913,17 @@ static int update_xps(struct dpaa2_eth_priv *priv)
 	for (i = 0; i < netdev_queues; i++) {
 		fq = &priv->fq[i % num_queues];
 
-		cpumask_clear(&xps_mask);
-		cpumask_set_cpu(fq->target_cpu, &xps_mask);
+		cpumask_clear(xps_mask);
+		cpumask_set_cpu(fq->target_cpu, xps_mask);
 
-		err = netif_set_xps_queue(net_dev, &xps_mask, i);
+		err = netif_set_xps_queue(net_dev, xps_mask, i);
 		if (err) {
 			netdev_warn_once(net_dev, "Error setting XPS queue\n");
 			break;
 		}
 	}
 
+	free_cpumask_var(xps_mask);
 	return err;
 }
 
-- 
2.27.0