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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Lukas Wunner <lukas@wunner.de>,
        Han Xu <han.xu@nxp.com>, Mark Brown <broonie@kernel.org>
Subject: [PATCH 5.9 218/252] spi: lpspi: Fix use-after-free on unbind
Date:   Mon, 23 Nov 2020 13:22:48 +0100
Message-Id: <20201123121846.095915656@linuxfoundation.org>
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From: Lukas Wunner <lukas@wunner.de>

commit 4def49da620c84a682d9361d6bef0a97eed46fe0 upstream.

Normally the last reference on an spi_controller is released by
spi_unregister_controller().  In the case of the i.MX lpspi driver,
the spi_controller is registered with devm_spi_register_controller(),
so spi_unregister_controller() is invoked automatically after the driver
has unbound.

However the driver already releases the last reference in
fsl_lpspi_remove() through a gratuitous call to spi_master_put(),
causing a use-after-free when spi_unregister_controller() is
subsequently invoked by the devres framework.

Fix by dropping the superfluous spi_master_put().

Fixes: 944c01a889d9 ("spi: lpspi: enable runtime pm for lpspi")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: <stable@vger.kernel.org> # v5.2+
Cc: Han Xu <han.xu@nxp.com>
Link: https://lore.kernel.org/r/ab3c0b18bd820501a12c85e440006e09ec0e275f.1604874488.git.lukas@wunner.de
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/spi/spi-fsl-lpspi.c |    3 ---
 1 file changed, 3 deletions(-)

--- a/drivers/spi/spi-fsl-lpspi.c
+++ b/drivers/spi/spi-fsl-lpspi.c
@@ -938,9 +938,6 @@ static int fsl_lpspi_remove(struct platf
 				spi_controller_get_devdata(controller);
 
 	pm_runtime_disable(fsl_lpspi->dev);
-
-	spi_master_put(controller);
-
 	return 0;
 }