Unverified Commit cc34d77d authored by Danilo Krummrich's avatar Danilo Krummrich Committed by Mark Brown
Browse files

spi: use generic driver_override infrastructure 

When a driver is probed through __driver_attach(), the bus' match()
callback is called without the device lock held, thus accessing the
driver_override field without a lock, which can cause a UAF.

Fix this by using the driver-core driver_override infrastructure taking
care of proper locking internally.

Note that calling match() from __driver_attach() without the device lock
held is intentional. [1]

Also note that we do not enable the driver_override feature of struct
bus_type, as SPI - in contrast to most other buses - passes "" to
sysfs_emit() when the driver_override pointer is NULL. Thus, printing
"\n" instead of "(null)\n".

Link: https://lore.kernel.org/driver-core/DGRGTIRHA62X.3RY09D9SOK77P@kernel.org/

 [1]
Reported-by: default avatarGui-Dong Han <hanguidong02@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220789


Fixes: 5039563e ("spi: Add driver_override SPI device attribute")
Signed-off-by: default avatarDanilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/20260324005919.2408620-12-dakr@kernel.org


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 63542bb4

drivers/spi/spi.c

+7 −12
Original line number Diff line number Diff line
@@ -50,7 +50,6 @@ static void spidev_release(struct device *dev) 
	struct spi_device	*spi = to_spi_device(dev);



	spi_controller_put(spi->controller);

	kfree(spi->driver_override);

	free_percpu(spi->pcpu_statistics);

	kfree(spi);

}
@@ -73,10 +72,9 @@ static ssize_t driver_override_store(struct device *dev, 
				     struct device_attribute *a,

				     const char *buf, size_t count)

{

	struct spi_device *spi = to_spi_device(dev);

	int ret;



	ret = driver_set_override(dev, &spi->driver_override, buf, count);

	ret = __device_set_driver_override(dev, buf, count);

	if (ret)

		return ret;
@@ -86,13 +84,8 @@ static ssize_t driver_override_store(struct device *dev, 
static ssize_t driver_override_show(struct device *dev,

				    struct device_attribute *a, char *buf)

{

	const struct spi_device *spi = to_spi_device(dev);

	ssize_t len;



	device_lock(dev);

	len = sysfs_emit(buf, "%s\n", spi->driver_override ? : "");

	device_unlock(dev);

	return len;

	guard(spinlock)(&dev->driver_override.lock);

	return sysfs_emit(buf, "%s\n", dev->driver_override.name ?: "");

}

static DEVICE_ATTR_RW(driver_override);
@@ -376,10 +369,12 @@ static int spi_match_device(struct device *dev, const struct device_driver *drv) 
{

	const struct spi_device	*spi = to_spi_device(dev);

	const struct spi_driver	*sdrv = to_spi_driver(drv);

	int ret;



	/* Check override first, and if set, only use the named driver */

	if (spi->driver_override)

		return strcmp(spi->driver_override, drv->name) == 0;

	ret = device_match_driver_override(dev, drv);

	if (ret >= 0)

		return ret;



	/* Attempt an OF style match */

	if (of_driver_match_device(dev, drv))

include/linux/spi/spi.h

+0 −5
Original line number Diff line number Diff line
@@ -159,10 +159,6 @@ extern void spi_transfer_cs_change_delay_exec(struct spi_message *msg, 
 * @modalias: Name of the driver to use with this device, or an alias

 *	for that name.  This appears in the sysfs "modalias" attribute

 *	for driver coldplugging, and in uevents used for hotplugging

 * @driver_override: If the name of a driver is written to this attribute, then

 *	the device will bind to the named driver and only the named driver.

 *	Do not set directly, because core frees it; use driver_set_override() to

 *	set or clear it.

 * @pcpu_statistics: statistics for the spi_device

 * @word_delay: delay to be inserted between consecutive

 *	words of a transfer
@@ -224,7 +220,6 @@ struct spi_device { 
	void			*controller_state;

	void			*controller_data;

	char			modalias[SPI_NAME_SIZE];

	const char		*driver_override;



	/* The statistics */

	struct spi_statistics __percpu	*pcpu_statistics;