[PATCH for-5.10] spi: rpc-if: Fix use-after-free on unbind

[Lukas Wunner <lukas@wunner.de>]

rpcif_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() helper which
keeps the private data accessible until the driver has unbound.

Fixes: eb8d6d464a27 ("spi: add Renesas RPC-IF driver")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: <stable@vger.kernel.org> # v5.9+: 5e844cc37a5c: spi: Introduce device-managed SPI controller allocation
Cc: <stable@vger.kernel.org> # v5.9+
Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
---
 drivers/spi/spi-rpc-if.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/spi/spi-rpc-if.c b/drivers/spi/spi-rpc-if.c
index ed3e548227f4..3579675485a5 100644
--- a/drivers/spi/spi-rpc-if.c
+++ b/drivers/spi/spi-rpc-if.c
@@ -134,7 +134,7 @@ static int rpcif_spi_probe(struct platform_device *pdev)
 	struct rpcif *rpc;
 	int error;
 
-	ctlr = spi_alloc_master(&pdev->dev, sizeof(*rpc));
+	ctlr = devm_spi_alloc_master(&pdev->dev, sizeof(*rpc));
 	if (!ctlr)
 		return -ENOMEM;
 
@@ -159,13 +159,8 @@ static int rpcif_spi_probe(struct platform_device *pdev)
 	error = spi_register_controller(ctlr);
 	if (error) {
 		dev_err(&pdev->dev, "spi_register_controller failed\n");
-		goto err_put_ctlr;
+		rpcif_disable_rpm(rpc);
 	}
-	return 0;
-
-err_put_ctlr:
-	rpcif_disable_rpm(rpc);
-	spi_controller_put(ctlr);
 
 	return error;
 }
-- 
2.28.0