Re: [PATCH v4 1/2] usb: gadget: f_fs: change ep->status safe in ffs_epfile_io()

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

On Sat, Jun 04, 2022 at 10:54:54AM +0800, Linyu Yuan wrote:
> If a task read/write data in blocking mode, it will wait the completion
> in ffs_epfile_io(), if function unbind occurs, ffs_func_unbind() will
> kfree ffs ep, once the task wake up, it still dereference the ffs ep to
> obtain the request status.
> 
> Fix it by moving the request status to io_data which is stack-safe.
> 
> Cc: <stable@vger.kernel.org> # 5.15
> Reported-by: Michael Wu <michael@allwinnertech.com>
> Tested-by: Michael Wu <michael@allwinnertech.com>
> Reviewed-by: John Keeping <john@metanate.com>
> Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>
> ---
> v2: correct interrupted assignment
> v3: add Reviewed-by and Reported-by
> v4: add Tetsed-by from Michael Wu,
>     remove one empty line
>     cc stable kernel
> 
>  drivers/usb/gadget/function/f_fs.c | 31 ++++++++++++++++---------------
>  1 file changed, 16 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> index 4585ee3..3958c60 100644
> --- a/drivers/usb/gadget/function/f_fs.c
> +++ b/drivers/usb/gadget/function/f_fs.c
> @@ -122,8 +122,6 @@ struct ffs_ep {
>  	struct usb_endpoint_descriptor	*descs[3];
>  
>  	u8				num;
> -
> -	int				status;	/* P: epfile->mutex */
>  };
>  
>  struct ffs_epfile {
> @@ -227,6 +225,9 @@ struct ffs_io_data {
>  	bool use_sg;
>  
>  	struct ffs_data *ffs;
> +
> +	int status;
> +	struct completion done;
>  };
>  
>  struct ffs_desc_helper {
> @@ -707,12 +708,12 @@ static const struct file_operations ffs_ep0_operations = {
>  
>  static void ffs_epfile_io_complete(struct usb_ep *_ep, struct usb_request *req)
>  {
> +	struct ffs_io_data *io_data = req->context;
> +
>  	ENTER();
> -	if (req->context) {
> -		struct ffs_ep *ep = _ep->driver_data;
> -		ep->status = req->status ? req->status : req->actual;
> -		complete(req->context);
> -	}
> +
> +	io_data->status = req->status ? req->status : req->actual;

Please do not use ? : lines unless you have to.  Please write this as
normal if () lines.

thanks,

greg k-h