Re: [PATCH] uacce: use filep->f_mapping to replace inode->i_mapping

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, May 11, 2023 at 10:15:53AM +0800, Zhangfei Gao wrote:
> The inode can be different in a container, for example, a docker and host
> both open the same uacce parent device, which uses the same uacce struct
> but different inode, so uacce->inode is not enough.
> 
> What's worse, when docker stops, the inode will be destroyed as well,
> causing use-after-free in uacce_remove.
> 
> So use q->filep->f_mapping to replace uacce->inode->i_mapping.
> 
> Signed-off-by: Weili Qian <qianweili@huawei.com>
> Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
> ---
>  drivers/misc/uacce/uacce.c | 16 +++++++++-------
>  include/linux/uacce.h      |  4 ++--
>  2 files changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/misc/uacce/uacce.c b/drivers/misc/uacce/uacce.c
> index 346bd7cf2e94..740ace422baa 100644
> --- a/drivers/misc/uacce/uacce.c
> +++ b/drivers/misc/uacce/uacce.c
> @@ -166,8 +166,8 @@ static int uacce_fops_open(struct inode *inode, struct file *filep)
>  
>  	init_waitqueue_head(&q->wait);
>  	filep->private_data = q;
> -	uacce->inode = inode;
>  	q->state = UACCE_Q_INIT;
> +	q->private_data = filep;
>  	mutex_init(&q->mutex);
>  	list_add(&q->list, &uacce->queues);
>  	mutex_unlock(&uacce->mutex);
> @@ -574,12 +574,6 @@ void uacce_remove(struct uacce_device *uacce)
>  
>  	if (!uacce)
>  		return;
> -	/*
> -	 * unmap remaining mapping from user space, preventing user still
> -	 * access the mmaped area while parent device is already removed
> -	 */
> -	if (uacce->inode)
> -		unmap_mapping_range(uacce->inode->i_mapping, 0, 0, 1);
>  
>  	/*
>  	 * uacce_fops_open() may be running concurrently, even after we remove
> @@ -589,6 +583,8 @@ void uacce_remove(struct uacce_device *uacce)
>  	mutex_lock(&uacce->mutex);
>  	/* ensure no open queue remains */
>  	list_for_each_entry_safe(q, next_q, &uacce->queues, list) {
> +		struct file *filep = q->private_data;
> +
>  		/*
>  		 * Taking q->mutex ensures that fops do not use the defunct
>  		 * uacce->ops after the queue is disabled.
> @@ -597,6 +593,12 @@ void uacce_remove(struct uacce_device *uacce)
>  		uacce_put_queue(q);
>  		mutex_unlock(&q->mutex);
>  		uacce_unbind_queue(q);
> +
> +		/*
> +		 * unmap remaining mapping from user space, preventing user still
> +		 * access the mmaped area while parent device is already removed
> +		 */
> +		unmap_mapping_range(filep->f_mapping, 0, 0, 1);
>  	}
>  
>  	/* disable sva now since no opened queues */
> diff --git a/include/linux/uacce.h b/include/linux/uacce.h
> index 0a81c3dfd26c..64b800b74436 100644
> --- a/include/linux/uacce.h
> +++ b/include/linux/uacce.h
> @@ -86,6 +86,7 @@ enum uacce_q_state {
>   * @state: queue state machine
>   * @pasid: pasid associated to the mm
>   * @handle: iommu_sva handle returned by iommu_sva_bind_device()
> + * @private_data: private data for saving filep
>   */
>  struct uacce_queue {
>  	struct uacce_device *uacce;
> @@ -97,6 +98,7 @@ struct uacce_queue {
>  	enum uacce_q_state state;
>  	u32 pasid;
>  	struct iommu_sva *handle;
> +	void *private_data;

Make this a real pointer to the inode, no need to make this "void *",
right?

thanks,

greg k-h