[PATCH 2/5] spi: fix statistics allocation

[Johan Hovold]

The controller per-cpu statistics is not allocated until after the
controller has been registered with driver core, which leaves a window
where accessing the sysfs attributes can trigger a NULL-pointer
dereference.

Fix this by moving the statistics allocation to controller allocation
while tying its lifetime to that of the controller (rather than using
implicit devres).

Fixes: 6598b91b5ac3 ("spi: spi.c: Convert statistics to per-cpu u64_stats_t")
Cc: stable@xxxxxxxxxxxxxxx	# 6.0
Cc: David Jander <david@xxxxxxxxxxx>
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
---
 drivers/spi/spi.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 9b2e307dc30a..53dee314d76a 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -3049,6 +3049,8 @@ static void spi_controller_release(struct device *dev)
 	struct spi_controller *ctlr;
 
 	ctlr = container_of(dev, struct spi_controller, dev);
+
+	free_percpu(ctlr->pcpu_statistics);
 	kfree(ctlr);
 }
 
@@ -3192,6 +3194,12 @@ struct spi_controller *__spi_alloc_controller(struct device *dev,
 	if (!ctlr)
 		return NULL;
 
+	ctlr->pcpu_statistics = spi_alloc_pcpu_stats(NULL);
+	if (!ctlr->pcpu_statistics) {
+		kfree(ctlr);
+		return NULL;
+	}
+
 	device_initialize(&ctlr->dev);
 	INIT_LIST_HEAD(&ctlr->queue);
 	spin_lock_init(&ctlr->queue_lock);
@@ -3483,13 +3491,6 @@ int spi_register_controller(struct spi_controller *ctlr)
 		if (status)
 			goto del_ctrl;
 	}
-	/* Add statistics */
-	ctlr->pcpu_statistics = spi_alloc_pcpu_stats(dev);
-	if (!ctlr->pcpu_statistics) {
-		dev_err(dev, "Error allocating per-cpu statistics\n");
-		status = -ENOMEM;
-		goto destroy_queue;
-	}
 
 	mutex_lock(&board_lock);
 	list_add_tail(&ctlr->list, &spi_controller_list);
@@ -3502,8 +3503,6 @@ int spi_register_controller(struct spi_controller *ctlr)
 	acpi_register_spi_devices(ctlr);
 	return status;
 
-destroy_queue:
-	spi_destroy_queue(ctlr);
 del_ctrl:
 	device_del(&ctlr->dev);
 free_bus_id:
-- 
2.52.0