Re: FAILED: patch "[PATCH] spi: bcm2835aux: Fix use-after-free on unbind" failed to apply to 4.19-stable tree

[Lukas Wunner <lukas@wunner.de>]

On Mon, Nov 23, 2020 at 09:54:04AM +0100, gregkh@linuxfoundation.org wrote:
> The patch below does not apply to the 4.19-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 <stable@vger.kernel.org>.

Below please find the backport of e13ee6cc4781 to linux-4.19.y.

Be aware that it depends on commit 5e844cc37a5c ("spi: Introduce
device-managed SPI controller allocation").

Thanks!

-- >8 --
Subject: [PATCH] spi: bcm2835aux: Fix use-after-free on unbind

[ Upstream commit e13ee6cc4781edaf8c7321bee19217e3702ed481 ]

bcm2835aux_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: b9dd3f6d4172 ("spi: bcm2835aux: Fix controller unregister order")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: <stable@vger.kernel.org> # v4.4+: 5e844cc37a5c: spi: Introduce device-managed SPI controller allocation
Cc: <stable@vger.kernel.org> # v4.4+: b9dd3f6d4172: spi: bcm2835aux: Fix controller unregister order
Cc: <stable@vger.kernel.org> # v4.4+
Link: https://lore.kernel.org/r/b290b06357d0c0bdee9cecc539b840a90630f101.1605121038.git.lukas@wunner.de
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi-bcm2835aux.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
index 11895c98aae3..8ea7e31b8c2f 100644
--- a/drivers/spi/spi-bcm2835aux.c
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -407,7 +407,7 @@ static int bcm2835aux_spi_probe(struct platform_device *pdev)
 	unsigned long clk_hz;
 	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;
@@ -439,30 +439,27 @@ static int bcm2835aux_spi_probe(struct platform_device *pdev)
 	/* the main area */
 	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 ((!bs->clk) || (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;
 	}
 
 	/* this also enables the HW block */
 	err = clk_prepare_enable(bs->clk);
 	if (err) {
 		dev_err(&pdev->dev, "could not prepare clock: %d\n", err);
-		goto out_master_put;
+		return err;
 	}
 
 	/* just checking if the clock returns a sane value */
@@ -495,8 +492,6 @@ static int bcm2835aux_spi_probe(struct platform_device *pdev)
 
 out_clk_disable:
 	clk_disable_unprepare(bs->clk);
-out_master_put:
-	spi_master_put(master);
 	return err;
 }
 
-- 
2.29.2