Call to rpmsg_ctrldev_ioctl() and rpmsg_ctrldev_remove() must be synchronized.
In present code rpmsg_ctrldev_remove() is not protected with lock, therefore
new char device creation can succeed through rpmsg_ctrldev_ioctl() call. At the
same time call to rpmsg_ctrldev_remove() funtion for ctrl device removal will
free associated rpdev device. As char device creation already succeeded, user
space is free to issue open() call which maps to rpmsg_create_ept() in kernel.
rpmsg_create_ept() function tries to reference rpdev which has already been
freed through rpmsg_ctrldev_remove(). Issue is predominantly seen in aggressive
reboot tests where rpmsg_ctrldev_ioctl() and rpmsg_ctrldev_remove() can race with
each other.
Adding lock in rpmsg_ctrldev_remove() avoids any new char device creation
throught rpmsg_ctrldev_ioctl() while remove call is already in progress.
Signed-off-by: Deepak Kumar Singh <[email protected]>
---
drivers/rpmsg/rpmsg_ctrl.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/rpmsg/rpmsg_ctrl.c b/drivers/rpmsg/rpmsg_ctrl.c
index 107da70..4332538 100644
--- a/drivers/rpmsg/rpmsg_ctrl.c
+++ b/drivers/rpmsg/rpmsg_ctrl.c
@@ -194,10 +194,12 @@ static void rpmsg_ctrldev_remove(struct rpmsg_device *rpdev)
struct rpmsg_ctrldev *ctrldev = dev_get_drvdata(&rpdev->dev);
int ret;
+ mutex_lock(&ctrldev->ctrl_lock);
/* Destroy all endpoints */
ret = device_for_each_child(&ctrldev->dev, NULL, rpmsg_chrdev_eptdev_destroy);
if (ret)
dev_warn(&rpdev->dev, "failed to nuke endpoints: %d\n", ret);
+ mutex_unlock(&ctrldev->ctrl_lock);
cdev_device_del(&ctrldev->cdev, &ctrldev->dev);
put_device(&ctrldev->dev);
--
2.7.4
On 9/15/2022 2:44 AM, Deepak Kumar Singh wrote:
> Call to rpmsg_ctrldev_ioctl() and rpmsg_ctrldev_remove() must be synchronized.
> In present code rpmsg_ctrldev_remove() is not protected with lock, therefore
> new char device creation can succeed through rpmsg_ctrldev_ioctl() call. At the
> same time call to rpmsg_ctrldev_remove() funtion for ctrl device removal will
nit: s/funtion/function/
> free associated rpdev device. As char device creation already succeeded, user
> space is free to issue open() call which maps to rpmsg_create_ept() in kernel.
> rpmsg_create_ept() function tries to reference rpdev which has already been
> freed through rpmsg_ctrldev_remove(). Issue is predominantly seen in aggressive
> reboot tests where rpmsg_ctrldev_ioctl() and rpmsg_ctrldev_remove() can race with
> each other.
>
> Adding lock in rpmsg_ctrldev_remove() avoids any new char device creation
> throught rpmsg_ctrldev_ioctl() while remove call is already in progress.
nit: s/throught/through/
>
> Signed-off-by: Deepak Kumar Singh <[email protected]>
> ---
> drivers/rpmsg/rpmsg_ctrl.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/rpmsg/rpmsg_ctrl.c b/drivers/rpmsg/rpmsg_ctrl.c
> index 107da70..4332538 100644
> --- a/drivers/rpmsg/rpmsg_ctrl.c
> +++ b/drivers/rpmsg/rpmsg_ctrl.c
> @@ -194,10 +194,12 @@ static void rpmsg_ctrldev_remove(struct rpmsg_device *rpdev)
> struct rpmsg_ctrldev *ctrldev = dev_get_drvdata(&rpdev->dev);
> int ret;
>
> + mutex_lock(&ctrldev->ctrl_lock);
> /* Destroy all endpoints */
> ret = device_for_each_child(&ctrldev->dev, NULL, rpmsg_chrdev_eptdev_destroy);
> if (ret)
> dev_warn(&rpdev->dev, "failed to nuke endpoints: %d\n", ret);
> + mutex_unlock(&ctrldev->ctrl_lock);
>
> cdev_device_del(&ctrldev->cdev, &ctrldev->dev);
> put_device(&ctrldev->dev);