Re: FAILED: patch "[PATCH] spi: bcm2835: Fix use-after-free on unbind" failed to apply to 5.9-stable tree

[Sudip Mukherjee <sudipm.mukherjee@gmail.com>]

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Hi Greg,

On Mon, Nov 23, 2020 at 09:54:23AM +0100, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 5.9-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 <stable@vger.kernel.org>.

Here is the backport.

--
Regards
Sudip

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From 357cbec3337f1ac35ccb87aaaddbb783b33c83b4 Mon Sep 17 00:00:00 2001
From: Lukas Wunner <lukas@wunner.de>
Date: Wed, 11 Nov 2020 20:07:20 +0100
Subject: [PATCH] spi: bcm2835: Fix use-after-free on unbind

commit e1483ac030fb4c57734289742f1c1d38dca61e22 upstream

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@pengutronix.de>
Reported-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: <stable@vger.kernel.org> # v3.10+: 123456789abc: spi: Introduce device-managed SPI controller allocation
Cc: <stable@vger.kernel.org> # v3.10+
Cc: Vladimir Oltean <olteanv@gmail.com>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/ad66e0a0ad96feb848814842ecf5b6a4539ef35c.1605121038.git.lukas@wunner.de
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
---
 drivers/spi/spi-bcm2835.c | 27 ++++++++-------------------
 1 file changed, 8 insertions(+), 19 deletions(-)

diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index 9605abaaec67..197485f2c2b2 100644
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -1278,7 +1278,7 @@ static int bcm2835_spi_probe(struct platform_device *pdev)
 	struct bcm2835_spi *bs;
 	int err;
 
-	ctlr = spi_alloc_master(&pdev->dev, ALIGN(sizeof(*bs),
+	ctlr = devm_spi_alloc_master(&pdev->dev, ALIGN(sizeof(*bs),
 						  dma_get_cache_alignment()));
 	if (!ctlr)
 		return -ENOMEM;
@@ -1299,26 +1299,17 @@ static int bcm2835_spi_probe(struct platform_device *pdev)
 	bs->ctlr = ctlr;
 
 	bs->regs = devm_platform_ioremap_resource(pdev, 0);
-	if (IS_ERR(bs->regs)) {
-		err = PTR_ERR(bs->regs);
-		goto out_controller_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);
-		if (err == -EPROBE_DEFER)
-			dev_dbg(&pdev->dev, "could not get clk: %d\n", err);
-		else
-			dev_err(&pdev->dev, "could not get clk: %d\n", err);
-		goto out_controller_put;
-	}
+	if (IS_ERR(bs->clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(bs->clk),
+				     "could not get clk\n");
 
 	bs->irq = platform_get_irq(pdev, 0);
-	if (bs->irq <= 0) {
-		err = bs->irq ? bs->irq : -ENODEV;
-		goto out_controller_put;
-	}
+	if (bs->irq <= 0)
+		return bs->irq ? bs->irq : -ENODEV;
 
 	clk_prepare_enable(bs->clk);
 
@@ -1352,8 +1343,6 @@ static int bcm2835_spi_probe(struct platform_device *pdev)
 	bcm2835_dma_release(ctlr, bs);
 out_clk_disable:
 	clk_disable_unprepare(bs->clk);
-out_controller_put:
-	spi_controller_put(ctlr);
 	return err;
 }
 
-- 
2.11.0