Re: FAILED: patch "[PATCH] spi: pxa2xx: Fix use-after-free on unbind" failed to apply to 4.14-stable tree

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

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Hi Greg,

On Mon, Dec 28, 2020 at 11:49:38AM +0100, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 4.14-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, will also apply to 4.9-stable and 4.4-stable.

--
Regards
Sudip

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From d0263dea6365ee31ca590e3866b8ca6a24cf456a Mon Sep 17 00:00:00 2001
From: Lukas Wunner <lukas@wunner.de>
Date: Mon, 7 Dec 2020 09:17:05 +0100
Subject: [PATCH] spi: pxa2xx: Fix use-after-free on unbind

commit 5626308bb94d9f930aa5f7c77327df4c6daa7759 upstream

pxa2xx_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/slave() helper
which keeps the private data accessible until the driver has unbound.

Fixes: 32e5b57232c0 ("spi: pxa2xx: Fix controller unregister order")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: <stable@vger.kernel.org> # v2.6.17+: 5e844cc37a5c: spi: Introduce device-managed SPI controller allocation
Cc: <stable@vger.kernel.org> # v2.6.17+: 32e5b57232c0: spi: pxa2xx: Fix controller unregister order
Cc: <stable@vger.kernel.org> # v2.6.17+
Link: https://lore.kernel.org/r/5764b04d4a6e43069ebb7808f64c2f774ac6f193.1607286887.git.lukas@wunner.de
Signed-off-by: Mark Brown <broonie@kernel.org>
[sudip: adjust context]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
---
 drivers/spi/spi-pxa2xx.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/spi/spi-pxa2xx.c b/drivers/spi/spi-pxa2xx.c
index 1579eb2bc29f..06eb7d259b7f 100644
--- a/drivers/spi/spi-pxa2xx.c
+++ b/drivers/spi/spi-pxa2xx.c
@@ -1660,7 +1660,7 @@ static int pxa2xx_spi_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
-	master = spi_alloc_master(dev, sizeof(struct driver_data));
+	master = devm_spi_alloc_master(dev, sizeof(*drv_data));
 	if (!master) {
 		dev_err(&pdev->dev, "cannot alloc spi_master\n");
 		pxa_ssp_free(ssp);
@@ -1841,7 +1841,6 @@ static int pxa2xx_spi_probe(struct platform_device *pdev)
 	free_irq(ssp->irq, drv_data);
 
 out_error_master_alloc:
-	spi_master_put(master);
 	pxa_ssp_free(ssp);
 	return status;
 }
-- 
2.11.0