spi: stm32: Fix use-after-free on unbind

stm32_spi_remove() accesses the driver's private data after calling
spi_unregister_master() even though that function releases the last
reference on the spi_master 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: 8d559a64 ("spi: stm32: drop devres version of spi_register_master")
Reported-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
Link: https://lore.kernel.org/r/1616052290-10887-1-git-send-email-alain.volmat@foss.st.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-stm32.c

@@ -1803,7 +1803,7 @@ static int stm32_spi_probe(struct platform_device *pdev)
 	struct reset_control *rst;
 	int ret;
 
-	master = spi_alloc_master(&pdev->dev, sizeof(struct stm32_spi));
+	master = devm_spi_alloc_master(&pdev->dev, sizeof(struct stm32_spi));
 	if (!master) {
 		dev_err(&pdev->dev, "spi master allocation failed\n");
 		return -ENOMEM;
@@ -1821,18 +1821,16 @@ static int stm32_spi_probe(struct platform_device *pdev)
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	spi->base = devm_ioremap_resource(&pdev->dev, res);
-	if (IS_ERR(spi->base)) {
-		ret = PTR_ERR(spi->base);
-		goto err_master_put;
-	}
+	if (IS_ERR(spi->base))
+		return PTR_ERR(spi->base);
 
 	spi->phys_addr = (dma_addr_t)res->start;
 
 	spi->irq = platform_get_irq(pdev, 0);
-	if (spi->irq <= 0) {
-		ret = dev_err_probe(&pdev->dev, spi->irq, "failed to get irq\n");
-		goto err_master_put;
-	}
+	if (spi->irq <= 0)
+		return dev_err_probe(&pdev->dev, spi->irq,
+				     "failed to get irq\n");
+
 	ret = devm_request_threaded_irq(&pdev->dev, spi->irq,
 					spi->cfg->irq_handler_event,
 					spi->cfg->irq_handler_thread,
@@ -1840,20 +1838,20 @@ static int stm32_spi_probe(struct platform_device *pdev)
 	if (ret) {
 		dev_err(&pdev->dev, "irq%d request failed: %d\n", spi->irq,
 			ret);
-		goto err_master_put;
+		return ret;
 	}
 
 	spi->clk = devm_clk_get(&pdev->dev, NULL);
 	if (IS_ERR(spi->clk)) {
 		ret = PTR_ERR(spi->clk);
 		dev_err(&pdev->dev, "clk get failed: %d\n", ret);
-		goto err_master_put;
+		return ret;
 	}
 
 	ret = clk_prepare_enable(spi->clk);
 	if (ret) {
 		dev_err(&pdev->dev, "clk enable failed: %d\n", ret);
-		goto err_master_put;
+		return ret;
 	}
 	spi->clk_rate = clk_get_rate(spi->clk);
 	if (!spi->clk_rate) {
@@ -1949,8 +1947,6 @@ static int stm32_spi_probe(struct platform_device *pdev)
 		dma_release_channel(spi->dma_rx);
 err_clk_disable:
 	clk_disable_unprepare(spi->clk);
-err_master_put:
-	spi_master_put(master);
 
 	return ret;
 }