[PATCH 6.18 163/309] spi: use generic driver_override infrastructure

Greg Kroah-Hartman
2026-03-31T17:05:32Z

From: Danilo Krummrich <dakr@kernel.org>

[ Upstream commit cc34d77dd48708d810c12bfd6f5bf03304f6c824 ]

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: 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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/spi/spi.c | 19 +++++++------------
include/linux/spi/spi.h | 5 -----
2 files changed, 7 insertions(+), 17 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 201b9569ce690..87d829d2a8427 100644
--- 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 cb2c2df310899..fe9dd430cc03a 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -156,10 +156,6 @@ 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
@@ -217,7 +213,6 @@ 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;
--
2.53.0