Commit 6c8dfb03 authored by Danilo Krummrich's avatar Danilo Krummrich
Browse files

bus: fsl-mc: 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]

Tested-by: default avatarIoana Ciornei <ioana.ciornei@nxp.com>
Acked-by: default avatarIoana Ciornei <ioana.ciornei@nxp.com>
Acked-by: default avatarChristophe Leroy (CS GROUP) <chleroy@kernel.org>
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: 1f86a00c ("bus/fsl-mc: add support for 'driver_override' in the mc-bus")
Link: https://patch.msgid.link/20260324005919.2408620-3-dakr@kernel.org


Signed-off-by: default avatarDanilo Krummrich <dakr@kernel.org>
parent 81d6f7c3

drivers/bus/fsl-mc/fsl-mc-bus.c

+7 −36
Original line number Diff line number Diff line
@@ -86,12 +86,16 @@ static int fsl_mc_bus_match(struct device *dev, const struct device_driver *drv) 
	struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);

	const struct fsl_mc_driver *mc_drv = to_fsl_mc_driver(drv);

	bool found = false;

	int ret;



	/* When driver_override is set, only bind to the matching driver */

	if (mc_dev->driver_override) {

		found = !strcmp(mc_dev->driver_override, mc_drv->driver.name);

	ret = device_match_driver_override(dev, drv);

	if (ret > 0) {

		found = true;

		goto out;

	}

	if (ret == 0)

		goto out;



	if (!mc_drv->match_id_table)

		goto out;
@@ -210,39 +214,8 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *attr, 
}

static DEVICE_ATTR_RO(modalias);



static ssize_t driver_override_store(struct device *dev,

				     struct device_attribute *attr,

				     const char *buf, size_t count)

{

	struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);

	int ret;



	if (WARN_ON(dev->bus != &fsl_mc_bus_type))

		return -EINVAL;



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

	if (ret)

		return ret;



	return count;

}



static ssize_t driver_override_show(struct device *dev,

				    struct device_attribute *attr, char *buf)

{

	struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);

	ssize_t len;



	device_lock(dev);

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

	device_unlock(dev);

	return len;

}

static DEVICE_ATTR_RW(driver_override);



static struct attribute *fsl_mc_dev_attrs[] = {

	&dev_attr_modalias.attr,

	&dev_attr_driver_override.attr,

	NULL,

};
@@ -345,6 +318,7 @@ ATTRIBUTE_GROUPS(fsl_mc_bus); 


const struct bus_type fsl_mc_bus_type = {

	.name = "fsl-mc",

	.driver_override = true,

	.match = fsl_mc_bus_match,

	.uevent = fsl_mc_bus_uevent,

	.probe = fsl_mc_probe,
@@ -910,9 +884,6 @@ static struct notifier_block fsl_mc_nb; 
 */

void fsl_mc_device_remove(struct fsl_mc_device *mc_dev)

{

	kfree(mc_dev->driver_override);

	mc_dev->driver_override = NULL;



	/*

	 * The device-specific remove callback will get invoked by device_del()

	 */

drivers/vfio/fsl-mc/vfio_fsl_mc.c

+1 −3
Original line number Diff line number Diff line
@@ -424,9 +424,7 @@ static int vfio_fsl_mc_bus_notifier(struct notifier_block *nb, 


	if (action == BUS_NOTIFY_ADD_DEVICE &&

	    vdev->mc_dev == mc_cont) {

		mc_dev->driver_override = kasprintf(GFP_KERNEL, "%s",

						    vfio_fsl_mc_ops.name);

		if (!mc_dev->driver_override)

		if (device_set_driver_override(dev, vfio_fsl_mc_ops.name))

			dev_warn(dev, "VFIO_FSL_MC: Setting driver override for device in dprc %s failed\n",

				 dev_name(&mc_cont->dev));

		else

include/linux/fsl/mc.h

+0 −4
Original line number Diff line number Diff line
@@ -178,9 +178,6 @@ struct fsl_mc_obj_desc { 
 * @regions: pointer to array of MMIO region entries

 * @irqs: pointer to array of pointers to interrupts allocated to this device

 * @resource: generic resource associated with this MC object device, if any.

 * @driver_override: driver name to force a match; do not set directly,

 *                   because core frees it; use driver_set_override() to

 *                   set or clear it.

 *

 * Generic device object for MC object devices that are "attached" to a

 * MC bus.
@@ -214,7 +211,6 @@ struct fsl_mc_device { 
	struct fsl_mc_device_irq **irqs;

	struct fsl_mc_resource *resource;

	struct device_link *consumer_link;

	const char *driver_override;

};



#define to_fsl_mc_device(_dev) \