[PATCH 5.10 648/717] spi: gpio: Dont leak SPI master in probe error path

Greg Kroah-Hartman
2020-12-28T14:32:54Z

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);