linux-kernel - [PATCH 4.4 32/39] spi: bcm2835: Fix use-after-free on unbind

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Date:   Thu, 10 Dec 2020 15:26:43 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Sascha Hauer <s.hauer@...gutronix.de>,
        Florian Fainelli <f.fainelli@...il.com>,
        Lukas Wunner <lukas@...ner.de>,
        Vladimir Oltean <olteanv@...il.com>,
        Mark Brown <broonie@...nel.org>
Subject: [PATCH 4.4 32/39] spi: bcm2835: Fix use-after-free on unbind

From: Lukas Wunner <lukas@...ner.de>

[ Upstream commit e1483ac030fb4c57734289742f1c1d38dca61e22 ]

bcm2835_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: f8043872e796 ("spi: add driver for BCM2835")
Reported-by: Sascha Hauer <s.hauer@...gutronix.de>
Reported-by: Florian Fainelli <f.fainelli@...il.com>
Signed-off-by: Lukas Wunner <lukas@...ner.de>
Cc: <stable@...r.kernel.org> # v3.10+: 5e844cc37a5c: spi: Introduce device-managed SPI controller allocation
Cc: <stable@...r.kernel.org> # v3.10+
Cc: Vladimir Oltean <olteanv@...il.com>
Tested-by: Florian Fainelli <f.fainelli@...il.com>
Acked-by: Florian Fainelli <f.fainelli@...il.com>
Link: https://lore.kernel.org/r/ad66e0a0ad96feb848814842ecf5b6a4539ef35c.1605121038.git.lukas@wunner.de
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/spi/spi-bcm2835.c |   15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -742,7 +742,7 @@ static int bcm2835_spi_probe(struct plat
 	struct resource *res;
 	int err;
 
-	master = spi_alloc_master(&pdev->dev, sizeof(*bs));
+	master = devm_spi_alloc_master(&pdev->dev, sizeof(*bs));
 	if (!master) {
 		dev_err(&pdev->dev, "spi_alloc_master() failed\n");
 		return -ENOMEM;
@@ -764,23 +764,20 @@ static int bcm2835_spi_probe(struct plat
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	bs->regs = devm_ioremap_resource(&pdev->dev, res);
-	if (IS_ERR(bs->regs)) {
-		err = PTR_ERR(bs->regs);
-		goto out_master_put;
-	}
+	if (IS_ERR(bs->regs))
+		return PTR_ERR(bs->regs);
 
 	bs->clk = devm_clk_get(&pdev->dev, NULL);
 	if (IS_ERR(bs->clk)) {
 		err = PTR_ERR(bs->clk);
 		dev_err(&pdev->dev, "could not get clk: %d\n", err);
-		goto out_master_put;
+		return err;
 	}
 
 	bs->irq = platform_get_irq(pdev, 0);
 	if (bs->irq <= 0) {
 		dev_err(&pdev->dev, "could not get IRQ: %d\n", bs->irq);
-		err = bs->irq ? bs->irq : -ENODEV;
-		goto out_master_put;
+		return bs->irq ? bs->irq : -ENODEV;
 	}
 
 	clk_prepare_enable(bs->clk);
@@ -808,8 +805,6 @@ static int bcm2835_spi_probe(struct plat
 
 out_clk_disable:
 	clk_disable_unprepare(bs->clk);
-out_master_put:
-	spi_master_put(master);
 	return err;
 }