From 7174dc655ef0578877b0b4598e69619d2be28b4d Mon Sep 17 00:00:00 2001 From: Lukas Wunner Date: Mon, 7 Dec 2020 09:17:09 +0100 Subject: [PATCH] spi: gpio: Don't leak SPI master in probe error path 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 Reviewed-by: Linus Walleij Cc: # v4.17+: 5e844cc37a5c: spi: Introduce device-managed SPI controller allocation Cc: # v5.1-: 8b797490b4db: spi: gpio: Make sure spi_master_put() is called in every error path Cc: # v5.1-: 45beec351998: spi: bitbang: Introduce spi_bitbang_init() Cc: # v5.1-: 79567c1a321e: spi: gpio: Use devm_spi_register_master() Cc: # v5.4-: d3b0ffa1d75d: spi: gpio: prevent memory leak in spi_gpio_probe Cc: # v4.17+ Cc: Navid Emamdoost Cc: Andrey Smirnov Link: https://lore.kernel.org/r/86eaed27431c3d709e3748eb76ceecbfc790dd37.1607286887.git.lukas@wunner.de Signed-off-by: Mark Brown --- drivers/spi/spi-gpio.c | 15 ++------------- 1 file changed, 2 insertions(+), 13 deletions(-) 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);