diff mbox series

[1/3] driver core: bus: introduce can_remove()

Message ID 20240202222603.141240-1-hamza.mahfooz@amd.com
State New
Headers
Series [1/3] driver core: bus: introduce can_remove() |

Commit Message

Hamza Mahfooz Feb. 2, 2024, 10:25 p.m. UTC 
  Currently, drivers have no mechanism to block requests to unbind
devices. However, this can cause resource leaks and leave the device in
an inconsistent state, such that rebinding the device may cause a hang
or otherwise prevent the device from being rebound. So, introduce
the can_remove() callback to allow drivers to indicate if it isn't
appropriate to remove a device at the given time.

Cc: stable@vger.kernel.org
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
---
 drivers/base/bus.c         | 4 ++++
 include/linux/device/bus.h | 2 ++
 2 files changed, 6 insertions(+)

Comments

Greg KH Feb. 2, 2024, 11:38 p.m. UTC | #1 
On Fri, Feb 02, 2024 at 05:25:54PM -0500, Hamza Mahfooz wrote:
> Currently, drivers have no mechanism to block requests to unbind
> devices.

And that is by design.

> However, this can cause resource leaks and leave the device in
> an inconsistent state, such that rebinding the device may cause a hang
> or otherwise prevent the device from being rebound.

That is a driver bug, please fix your driver.

> So, introduce the can_remove() callback to allow drivers to indicate
> if it isn't appropriate to remove a device at the given time.

Nope, sorry, the driver needs to be fixed.

What broken driver are you needing this for?

Also realize, only root can unbind drivers (and it can also unload
modules), so if the root user really wants to do this, it can, and
should be possible to.

sorry,

greg k-h
Christian König Feb. 5, 2024, 8:48 a.m. UTC | #2 
Am 02.02.24 um 23:25 schrieb Hamza Mahfooz:
> Currently, drivers have no mechanism to block requests to unbind
> devices. However, this can cause resource leaks and leave the device in
> an inconsistent state, such that rebinding the device may cause a hang
> or otherwise prevent the device from being rebound. So, introduce
> the can_remove() callback to allow drivers to indicate if it isn't
> appropriate to remove a device at the given time.

Well that is nonsense. When you physically remove a device (e.g. unplug 
it) then there is nothing in software you can do to prevent that.

Regards,
Christian.

>
> Cc: stable@vger.kernel.org
> Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
> ---
>   drivers/base/bus.c         | 4 ++++
>   include/linux/device/bus.h | 2 ++
>   2 files changed, 6 insertions(+)
>
> diff --git a/drivers/base/bus.c b/drivers/base/bus.c
> index daee55c9b2d9..7c259b01ea99 100644
> --- a/drivers/base/bus.c
> +++ b/drivers/base/bus.c
> @@ -239,6 +239,10 @@ static ssize_t unbind_store(struct device_driver *drv, const char *buf,
>   
>   	dev = bus_find_device_by_name(bus, NULL, buf);
>   	if (dev && dev->driver == drv) {
> +		if (dev->bus && dev->bus->can_remove &&
> +		    !dev->bus->can_remove(dev))
> +			return -EBUSY;
> +
>   		device_driver_detach(dev);
>   		err = count;
>   	}
> diff --git a/include/linux/device/bus.h b/include/linux/device/bus.h
> index 5ef4ec1c36c3..c9d4af0ed3b8 100644
> --- a/include/linux/device/bus.h
> +++ b/include/linux/device/bus.h
> @@ -46,6 +46,7 @@ struct fwnode_handle;
>    *		be called at late_initcall_sync level. If the device has
>    *		consumers that are never bound to a driver, this function
>    *		will never get called until they do.
> + * @can_remove: Called before attempting to remove a device from this bus.
>    * @remove:	Called when a device removed from this bus.
>    * @shutdown:	Called at shut-down time to quiesce the device.
>    *
> @@ -85,6 +86,7 @@ struct bus_type {
>   	int (*uevent)(const struct device *dev, struct kobj_uevent_env *env);
>   	int (*probe)(struct device *dev);
>   	void (*sync_state)(struct device *dev);
> +	bool (*can_remove)(struct device *dev);
>   	void (*remove)(struct device *dev);
>   	void (*shutdown)(struct device *dev);
>
diff mbox series

Patch

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index daee55c9b2d9..7c259b01ea99 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -239,6 +239,10 @@  static ssize_t unbind_store(struct device_driver *drv, const char *buf,
 
 	dev = bus_find_device_by_name(bus, NULL, buf);
 	if (dev && dev->driver == drv) {
+		if (dev->bus && dev->bus->can_remove &&
+		    !dev->bus->can_remove(dev))
+			return -EBUSY;
+
 		device_driver_detach(dev);
 		err = count;
 	}
diff --git a/include/linux/device/bus.h b/include/linux/device/bus.h
index 5ef4ec1c36c3..c9d4af0ed3b8 100644
--- a/include/linux/device/bus.h
+++ b/include/linux/device/bus.h
@@ -46,6 +46,7 @@  struct fwnode_handle;
  *		be called at late_initcall_sync level. If the device has
  *		consumers that are never bound to a driver, this function
  *		will never get called until they do.
+ * @can_remove: Called before attempting to remove a device from this bus.
  * @remove:	Called when a device removed from this bus.
  * @shutdown:	Called at shut-down time to quiesce the device.
  *
@@ -85,6 +86,7 @@  struct bus_type {
 	int (*uevent)(const struct device *dev, struct kobj_uevent_env *env);
 	int (*probe)(struct device *dev);
 	void (*sync_state)(struct device *dev);
+	bool (*can_remove)(struct device *dev);
 	void (*remove)(struct device *dev);
 	void (*shutdown)(struct device *dev);