linux-kernel - [PATCH net] enetc: Fix illegal access when reading affinity

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Date:   Fri, 17 Sep 2021 13:22:05 +0300
From:   Claudiu Manoil <claudiu.manoil@....com>
To:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH net] enetc: Fix illegal access when reading affinity_hint

irq_set_affinity_hit() stores a reference to the cpumask_t
parameter in the irq descriptor, and that reference can be
accessed later from irq_affinity_hint_proc_show(). Since
the cpu_mask parameter passed to irq_set_affinity_hit() has
only temporary storage (it's on the stack memory), later
accesses to it are illegal. Thus reads from the corresponding
procfs affinity_hint file can result in paging request oops.

The issue is fixed by the get_cpu_mask() helper, which provides
a permanent storage for the cpumask_t parameter.

Fixes: d4fd0404c1c9 ("enetc: Introduce basic PF and VF ENETC ethernet drivers")
Signed-off-by: Claudiu Manoil <claudiu.manoil@....com>
---
 drivers/net/ethernet/freescale/enetc/enetc.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
index 3ca93adb9662..7f90c27c0e79 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc.c
@@ -1879,7 +1879,6 @@ static void enetc_clear_bdrs(struct enetc_ndev_priv *priv)
 static int enetc_setup_irqs(struct enetc_ndev_priv *priv)
 {
 	struct pci_dev *pdev = priv->si->pdev;
-	cpumask_t cpu_mask;
 	int i, j, err;
 
 	for (i = 0; i < priv->bdr_int_num; i++) {
@@ -1908,9 +1907,7 @@ static int enetc_setup_irqs(struct enetc_ndev_priv *priv)
 
 			enetc_wr(hw, ENETC_SIMSITRV(idx), entry);
 		}
-		cpumask_clear(&cpu_mask);
-		cpumask_set_cpu(i % num_online_cpus(), &cpu_mask);
-		irq_set_affinity_hint(irq, &cpu_mask);
+		irq_set_affinity_hint(irq, get_cpu_mask(i % num_online_cpus()));
 	}
 
 	return 0;
-- 
2.25.1