[PATCH net,v2] net: mana: Fix accessing freed irq affinity_hint

[Haiyang Zhang <haiyangz@microsoft.com>]

After calling irq_set_affinity_and_hint(), the cpumask pointer is
saved in desc->affinity_hint, and will be used later when reading
/proc/irq/<num>/affinity_hint. So the cpumask variable needs to be
persistent. Otherwise, we are accessing freed memory when reading
the affinity_hint file.

Also, need to clear affinity_hint before free_irq(), otherwise there
is a one-time warning and stack trace during module unloading:

 [  243.948687] WARNING: CPU: 10 PID: 1589 at kernel/irq/manage.c:1913 free_irq+0x318/0x360
 ...
 [  243.948753] Call Trace:
 [  243.948754]  <TASK>
 [  243.948760]  mana_gd_remove_irqs+0x78/0xc0 [mana]
 [  243.948767]  mana_gd_remove+0x3e/0x80 [mana]
 [  243.948773]  pci_device_remove+0x3d/0xb0
 [  243.948778]  device_remove+0x46/0x70
 [  243.948782]  device_release_driver_internal+0x1fe/0x280
 [  243.948785]  driver_detach+0x4e/0xa0
 [  243.948787]  bus_remove_driver+0x70/0xf0
 [  243.948789]  driver_unregister+0x35/0x60
 [  243.948792]  pci_unregister_driver+0x44/0x90
 [  243.948794]  mana_driver_exit+0x14/0x3fe [mana]
 [  243.948800]  __do_sys_delete_module.constprop.0+0x185/0x2f0

To fix the bug, use the persistent mask, cpumask_of(cpu#), and set
affinity_hint to NULL before freeing the IRQ, as required by free_irq().

Cc: stable@vger.kernel.org
Fixes: 71fa6887eeca ("net: mana: Assign interrupts to CPUs based on NUMA nodes")
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
---
 .../net/ethernet/microsoft/mana/gdma_main.c   | 35 ++++++-------------
 1 file changed, 10 insertions(+), 25 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
index b144f2237748..a55d42332e20 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -1218,8 +1218,6 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
 	struct gdma_context *gc = pci_get_drvdata(pdev);
 	struct gdma_irq_context *gic;
 	unsigned int max_irqs;
-	u16 *cpus;
-	cpumask_var_t req_mask;
 	int nvec, irq;
 	int err, i = 0, j;
 
@@ -1240,21 +1238,7 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
 		goto free_irq_vector;
 	}
 
-	if (!zalloc_cpumask_var(&req_mask, GFP_KERNEL)) {
-		err = -ENOMEM;
-		goto free_irq;
-	}
-
-	cpus = kcalloc(nvec, sizeof(*cpus), GFP_KERNEL);
-	if (!cpus) {
-		err = -ENOMEM;
-		goto free_mask;
-	}
-	for (i = 0; i < nvec; i++)
-		cpus[i] = cpumask_local_spread(i, gc->numa_node);
-
 	for (i = 0; i < nvec; i++) {
-		cpumask_set_cpu(cpus[i], req_mask);
 		gic = &gc->irq_contexts[i];
 		gic->handler = NULL;
 		gic->arg = NULL;
@@ -1269,17 +1253,16 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
 		irq = pci_irq_vector(pdev, i);
 		if (irq < 0) {
 			err = irq;
-			goto free_mask;
+			goto free_irq;
 		}
 
 		err = request_irq(irq, mana_gd_intr, 0, gic->name, gic);
 		if (err)
-			goto free_mask;
-		irq_set_affinity_and_hint(irq, req_mask);
-		cpumask_clear(req_mask);
+			goto free_irq;
+
+		irq_set_affinity_and_hint(irq, cpumask_of(cpumask_local_spread
+					  (i, gc->numa_node)));
 	}
-	free_cpumask_var(req_mask);
-	kfree(cpus);
 
 	err = mana_gd_alloc_res_map(nvec, &gc->msix_resource);
 	if (err)
@@ -1290,13 +1273,12 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
 
 	return 0;
 
-free_mask:
-	free_cpumask_var(req_mask);
-	kfree(cpus);
 free_irq:
 	for (j = i - 1; j >= 0; j--) {
 		irq = pci_irq_vector(pdev, j);
 		gic = &gc->irq_contexts[j];
+
+		irq_update_affinity_hint(irq, NULL);
 		free_irq(irq, gic);
 	}
 
@@ -1324,6 +1306,9 @@ static void mana_gd_remove_irqs(struct pci_dev *pdev)
 			continue;
 
 		gic = &gc->irq_contexts[i];
+
+		/* Need to clear the hint before free_irq */
+		irq_update_affinity_hint(irq, NULL);
 		free_irq(irq, gic);
 	}
 
-- 
2.25.1