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/
Reported-by: Gui-Dong Han <hanguidong02@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220789
Fixes: 5039563e7c25 ("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>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 53dee314d76ae91f37f2f137fcf7bc2fad69a381..4101c2803eb31e67fc5c28a51043ac2bf7b751ba 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -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))

diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index af7cfee7b8f60d7e022cb82e7fe2dbd3e37bf617..0dc671c07d3a8ab1b0e361440962090455dcf987 100644 (file)
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -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;