FAILED: patch "[PATCH] spi: pxa2xx: Fix use-after-free on unbind" failed to apply to 4.9-stable tree

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 5626308bb94d9f930aa5f7c77327df4c6daa7759 Mon Sep 17 00:00:00 2001
From: Lukas Wunner <[email protected]>
Date: Mon, 7 Dec 2020 09:17:05 +0100
Subject: [PATCH] spi: pxa2xx: Fix use-after-free on unbind

pxa2xx_spi_remove() accesses the driver's private data after calling spi_unregister_controller() even though that function releases the last reference on the spi_controller and thereby frees the private data.

Fix by switching over to the new devm_spi_alloc_master/slave() helper which keeps the private data accessible until the driver has unbound.

index 62a0f0f86553..bd2354fd438d 100644
@@ -1691,9 +1691,9 @@ static int pxa2xx_spi_probe(struct platform_device *pdev)
 	}
 
 	if (platform_info->is_slave)
-		controller = spi_alloc_slave(dev, sizeof(struct driver_data));
+		controller = devm_spi_alloc_slave(dev, sizeof(*drv_data));
 	else
-		controller = spi_alloc_master(dev, sizeof(struct driver_data));
+		controller = devm_spi_alloc_master(dev, sizeof(*drv_data));
 
 	if (!controller) {
 		dev_err(&pdev->dev, "cannot alloc spi_controller\n");

@@ -1916,7 +1916,6 @@ static int pxa2xx_spi_probe(struct platform_device *pdev)
 	free_irq(ssp->irq, drv_data);
 
 out_error_controller_alloc:
-	spi_controller_put(controller);
 	pxa_ssp_free(ssp);
 	return status;
 }