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spi: use generic driver_override infrastructure

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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: Gui-Dong Han <hanguidong02@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220789
Fixes: 5039563e7c ("spi: Add driver_override SPI device attribute")
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/20260324005919.2408620-12-dakr@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Danilo Krummrich 2026-03-24 01:59:15 +01:00 committed by Mark Brown
parent 63542bb402
commit cc34d77dd4
No known key found for this signature in database
GPG Key ID: 24D68B725D5487D0
2 changed files with 7 additions and 17 deletions
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19
drivers/spi/spi.c
View File

@ -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))

5
include/linux/spi/spi.h
View File

@ -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;