Re: [PATCH 07/12] rpmsg: use generic driver_override infrastructure

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Mon, 23 Mar 2026 at 19:00, Danilo Krummrich <dakr@kernel.org> wrote:
>
> 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]
>
> 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: e95060478244 ("rpmsg: Introduce a driver override mechanism")
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  drivers/rpmsg/qcom_glink_native.c |  2 --

For the below files:

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>

>  drivers/rpmsg/rpmsg_core.c        | 43 +++++--------------------------
>  drivers/rpmsg/virtio_rpmsg_bus.c  |  1 -
>  include/linux/rpmsg.h             |  4 ---
>  4 files changed, 7 insertions(+), 43 deletions(-)
>
> diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
> index 9ef17c2e45b0..e9d1b2082477 100644
> --- a/drivers/rpmsg/qcom_glink_native.c
> +++ b/drivers/rpmsg/qcom_glink_native.c
> @@ -1623,7 +1623,6 @@ static void qcom_glink_rpdev_release(struct device *dev)
>  {
>         struct rpmsg_device *rpdev = to_rpmsg_device(dev);
>
> -       kfree(rpdev->driver_override);
>         kfree(rpdev);
>  }
>
> @@ -1859,7 +1858,6 @@ static void qcom_glink_device_release(struct device *dev)
>
>         /* Release qcom_glink_alloc_channel() reference */
>         kref_put(&channel->refcount, qcom_glink_channel_release);
> -       kfree(rpdev->driver_override);
>         kfree(rpdev);
>  }
>
> diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c
> index 96964745065b..2b9f6d5a9a4f 100644
> --- a/drivers/rpmsg/rpmsg_core.c
> +++ b/drivers/rpmsg/rpmsg_core.c
> @@ -358,33 +358,6 @@ rpmsg_show_attr(src, src, "0x%x\n");
>  rpmsg_show_attr(dst, dst, "0x%x\n");
>  rpmsg_show_attr(announce, announce ? "true" : "false", "%s\n");
>
> -static ssize_t driver_override_store(struct device *dev,
> -                                    struct device_attribute *attr,
> -                                    const char *buf, size_t count)
> -{
> -       struct rpmsg_device *rpdev = to_rpmsg_device(dev);
> -       int ret;
> -
> -       ret = driver_set_override(dev, &rpdev->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 rpmsg_device *rpdev = to_rpmsg_device(dev);
> -       ssize_t len;
> -
> -       device_lock(dev);
> -       len = sysfs_emit(buf, "%s\n", rpdev->driver_override);
> -       device_unlock(dev);
> -       return len;
> -}
> -static DEVICE_ATTR_RW(driver_override);
> -
>  static ssize_t modalias_show(struct device *dev,
>                              struct device_attribute *attr, char *buf)
>  {
> @@ -405,7 +378,6 @@ static struct attribute *rpmsg_dev_attrs[] = {
>         &dev_attr_dst.attr,
>         &dev_attr_src.attr,
>         &dev_attr_announce.attr,
> -       &dev_attr_driver_override.attr,
>         NULL,
>  };
>  ATTRIBUTE_GROUPS(rpmsg_dev);
> @@ -424,9 +396,11 @@ static int rpmsg_dev_match(struct device *dev, const struct device_driver *drv)
>         const struct rpmsg_driver *rpdrv = to_rpmsg_driver(drv);
>         const struct rpmsg_device_id *ids = rpdrv->id_table;
>         unsigned int i;
> +       int ret;
>
> -       if (rpdev->driver_override)
> -               return !strcmp(rpdev->driver_override, drv->name);
> +       ret = device_match_driver_override(dev, drv);
> +       if (ret >= 0)
> +               return ret;
>
>         if (ids)
>                 for (i = 0; ids[i].name[0]; i++)
> @@ -535,6 +509,7 @@ static const struct bus_type rpmsg_bus = {
>         .name           = "rpmsg",
>         .match          = rpmsg_dev_match,
>         .dev_groups     = rpmsg_dev_groups,
> +       .driver_override = true,
>         .uevent         = rpmsg_uevent,
>         .probe          = rpmsg_dev_probe,
>         .remove         = rpmsg_dev_remove,
> @@ -560,11 +535,9 @@ int rpmsg_register_device_override(struct rpmsg_device *rpdev,
>
>         device_initialize(dev);
>         if (driver_override) {
> -               ret = driver_set_override(dev, &rpdev->driver_override,
> -                                         driver_override,
> -                                         strlen(driver_override));
> +               ret = device_set_driver_override(dev, driver_override);
>                 if (ret) {
> -                       dev_err(dev, "device_set_override failed: %d\n", ret);
> +                       dev_err(dev, "device_set_driver_override() failed: %d\n", ret);
>                         put_device(dev);
>                         return ret;
>                 }
> @@ -573,8 +546,6 @@ int rpmsg_register_device_override(struct rpmsg_device *rpdev,
>         ret = device_add(dev);
>         if (ret) {
>                 dev_err(dev, "device_add failed: %d\n", ret);
> -               kfree(rpdev->driver_override);
> -               rpdev->driver_override = NULL;
>                 put_device(dev);
>         }
>
> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
> index 8d9e2b4dc7c1..e0dacb736ef9 100644
> --- a/drivers/rpmsg/virtio_rpmsg_bus.c
> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
> @@ -373,7 +373,6 @@ static void virtio_rpmsg_release_device(struct device *dev)
>         struct rpmsg_device *rpdev = to_rpmsg_device(dev);
>         struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
>
> -       kfree(rpdev->driver_override);
>         kfree(vch);
>  }
>
> diff --git a/include/linux/rpmsg.h b/include/linux/rpmsg.h
> index fb7ab9165645..c2e3ef8480d5 100644
> --- a/include/linux/rpmsg.h
> +++ b/include/linux/rpmsg.h
> @@ -41,9 +41,6 @@ struct rpmsg_channel_info {
>   * rpmsg_device - device that belong to the rpmsg bus
>   * @dev: the device struct
>   * @id: device id (used to match between rpmsg drivers and devices)
> - * @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.
>   * @src: local address
>   * @dst: destination address
>   * @ept: the rpmsg endpoint of this channel
> @@ -53,7 +50,6 @@ struct rpmsg_channel_info {
>  struct rpmsg_device {
>         struct device dev;
>         struct rpmsg_device_id id;
> -       const char *driver_override;
>         u32 src;
>         u32 dst;
>         struct rpmsg_endpoint *ept;
> --
> 2.53.0
>