| Message ID | 49102f5bbb3f1592d9cfd7b39ac5e131a031f950.1605512876.git.lukas@wunner.de |
|---|---|
| State | Accepted |
| Commit | 7174dc655ef0578877b0b4598e69619d2be28b4d |
| Headers | show |
| Series | [for-5.10] spi: gpio: Don't leak SPI master in probe error path | expand |
On Mon, Nov 16, 2020 at 9:44 AM Lukas Wunner <lukas@wunner.de> wrote: > 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> > 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> > Cc: Linus Walleij <linus.walleij@linaro.org> That's a really good fix. Thanks to looking into this! Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Yours, Linus Walleij
diff --git a/drivers/spi/spi-gpio.c b/drivers/spi/spi-gpio.c index 7ceb0ba27b75..0584f4d2fde2 100644 --- a/drivers/spi/spi-gpio.c +++ b/drivers/spi/spi-gpio.c @@ -350,11 +350,6 @@ static int spi_gpio_probe_pdata(struct platform_device *pdev, 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 platform_device *pdev) 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 platform_device *pdev) 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);
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> 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> Cc: Linus Walleij <linus.walleij@linaro.org> --- drivers/spi/spi-gpio.c | 15 ++------------- 1 file changed, 2 insertions(+), 13 deletions(-)