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    Subject[PATCH 5.10 648/717] spi: gpio: Dont leak SPI master in probe error path
    Date
    From: Lukas Wunner <lukas@wunner.de>

    commit 7174dc655ef0578877b0b4598e69619d2be28b4d upstream.

    If the call to devm_spi_register_master() fails on probe of the GPIO SPI
    driver, the spi_master struct is erroneously not freed:

    After allocating the spi_master, its reference count is 1. The driver
    unconditionally decrements the reference count on unbind using a devm
    action. Before calling devm_spi_register_master(), the driver
    unconditionally increments the reference count because on success,
    that function will decrement the reference count on unbind. However on
    failure, devm_spi_register_master() does *not* decrement the reference
    count, so the spi_master is leaked.

    The issue was introduced by commits 8b797490b4db ("spi: gpio: Make sure
    spi_master_put() is called in every error path") and 79567c1a321e ("spi:
    gpio: Use devm_spi_register_master()"), which sought to plug leaks
    introduced by 9b00bc7b901f ("spi: spi-gpio: Rewrite to use GPIO
    descriptors") but missed this remaining leak.

    The situation was later aggravated by commit d3b0ffa1d75d ("spi: gpio:
    prevent memory leak in spi_gpio_probe"), which introduced a
    use-after-free because it releases a reference on the spi_master if
    devm_add_action_or_reset() fails even though the function already
    does that.

    Fix by switching over to the new devm_spi_alloc_master() helper.

    Fixes: 9b00bc7b901f ("spi: spi-gpio: Rewrite to use GPIO descriptors")
    Signed-off-by: Lukas Wunner <lukas@wunner.de>
    Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
    Cc: <stable@vger.kernel.org> # v4.17+: 5e844cc37a5c: spi: Introduce device-managed SPI controller allocation
    Cc: <stable@vger.kernel.org> # v5.1-: 8b797490b4db: spi: gpio: Make sure spi_master_put() is called in every error path
    Cc: <stable@vger.kernel.org> # v5.1-: 45beec351998: spi: bitbang: Introduce spi_bitbang_init()
    Cc: <stable@vger.kernel.org> # v5.1-: 79567c1a321e: spi: gpio: Use devm_spi_register_master()
    Cc: <stable@vger.kernel.org> # v5.4-: d3b0ffa1d75d: spi: gpio: prevent memory leak in spi_gpio_probe
    Cc: <stable@vger.kernel.org> # v4.17+
    Cc: Navid Emamdoost <navid.emamdoost@gmail.com>
    Cc: Andrey Smirnov <andrew.smirnov@gmail.com>
    Link: https://lore.kernel.org/r/86eaed27431c3d709e3748eb76ceecbfc790dd37.1607286887.git.lukas@wunner.de
    Signed-off-by: Mark Brown <broonie@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/spi/spi-gpio.c | 15 ++-------------
    1 file changed, 2 insertions(+), 13 deletions(-)

    --- a/drivers/spi/spi-gpio.c
    +++ b/drivers/spi/spi-gpio.c
    @@ -350,11 +350,6 @@ static int spi_gpio_probe_pdata(struct p
    return 0;
    }

    -static void spi_gpio_put(void *data)
    -{
    - spi_master_put(data);
    -}
    -
    static int spi_gpio_probe(struct platform_device *pdev)
    {
    int status;
    @@ -363,16 +358,10 @@ static int spi_gpio_probe(struct platfor
    struct device *dev = &pdev->dev;
    struct spi_bitbang *bb;

    - master = spi_alloc_master(dev, sizeof(*spi_gpio));
    + master = devm_spi_alloc_master(dev, sizeof(*spi_gpio));
    if (!master)
    return -ENOMEM;

    - status = devm_add_action_or_reset(&pdev->dev, spi_gpio_put, master);
    - if (status) {
    - spi_master_put(master);
    - return status;
    - }
    -
    if (pdev->dev.of_node)
    status = spi_gpio_probe_dt(pdev, master);
    else
    @@ -432,7 +421,7 @@ static int spi_gpio_probe(struct platfor
    if (status)
    return status;

    - return devm_spi_register_master(&pdev->dev, spi_master_get(master));
    + return devm_spi_register_master(&pdev->dev, master);
    }

    MODULE_ALIAS("platform:" DRIVER_NAME);

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