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    Subject[PATCH 5.9 218/252] spi: lpspi: Fix use-after-free on unbind
    Date
    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;
    }


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