[PATCH net, 2/2] net: mana: Fix accessing freed irq affinity_hint

[Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>]

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
allocated per irq, and available until freeing the irq. Otherwise,
we are accessing freed memory when reading the affinity_hint file.

To fix the bug, allocate the cpumask per irq, and free it just
before freeing the irq.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 71fa6887eeca ("net: mana: Assign interrupts to CPUs based on NUMA nodes")
Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
---
 .../net/ethernet/microsoft/mana/gdma_main.c   | 40 ++++++++++---------
 include/net/mana/gdma.h                       |  1 +
 2 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
index 3bae9d4c1f08..37473ae3859c 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -1219,7 +1219,6 @@ static int mana_gd_setup_irqs(struct pci_dev *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;
 
@@ -1240,25 +1239,26 @@ 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;
+		goto free_gic;
 	}
 	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;
 
+		if (!zalloc_cpumask_var(&gic->cpu_hint, GFP_KERNEL)) {
+			err = -ENOMEM;
+			goto free_irq;
+		}
+
+		cpumask_set_cpu(cpus[i], gic->cpu_hint);
+
 		if (!i)
 			snprintf(gic->name, MANA_IRQ_NAME_SZ, "mana_hwc@pci:%s",
 				 pci_name(pdev));
@@ -1269,17 +1269,18 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
 		irq = pci_irq_vector(pdev, i);
 		if (irq < 0) {
 			err = irq;
-			goto free_mask;
+			free_cpumask_var(gic->cpu_hint);
+			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);
+		if (err) {
+			free_cpumask_var(gic->cpu_hint);
+			goto free_irq;
+		}
+
+		irq_set_affinity_and_hint(irq, gic->cpu_hint);
 	}
-	free_cpumask_var(req_mask);
-	kfree(cpus);
 
 	err = mana_gd_alloc_res_map(nvec, &gc->msix_resource);
 	if (err)
@@ -1288,20 +1289,22 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
 	gc->max_num_msix = nvec;
 	gc->num_msix_usable = nvec;
 
+	kfree(cpus);
 	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_cpumask_var(gic->cpu_hint);
 		free_irq(irq, gic);
 	}
 
+	kfree(cpus);
+
+free_gic:
 	kfree(gc->irq_contexts);
 	gc->irq_contexts = NULL;
 free_irq_vector:
@@ -1329,6 +1332,7 @@ static void mana_gd_remove_irqs(struct pci_dev *pdev)
 
 		/* Need to clear the hint before free_irq */
 		irq_update_affinity_hint(irq, NULL);
+		free_cpumask_var(gic->cpu_hint);
 		free_irq(irq, gic);
 	}
 
diff --git a/include/net/mana/gdma.h b/include/net/mana/gdma.h
index 56189e4252da..4dcafecbd89e 100644
--- a/include/net/mana/gdma.h
+++ b/include/net/mana/gdma.h
@@ -342,6 +342,7 @@ struct gdma_irq_context {
 	void (*handler)(void *arg);
 	void *arg;
 	char name[MANA_IRQ_NAME_SZ];
+	cpumask_var_t cpu_hint;
 };
 
 struct gdma_context {
-- 
2.25.1