On Thu, Dec 12, 2019 at 4:38 PM Peter Chen peter.chen@nxp.com wrote:

The UDC core uses req->num_sgs to judge if scatter buffer list is used. Eg: usb_gadget_map_request_by_dev. For f_fs sync io mode, the request is re-used for each request, so if the 1st request->length > PAGE_SIZE, and the 2nd request->length is <= PAGE_SIZE, the f_fs uses the 1st req->num_sgs for the 2nd request, it causes the UDC core get the wrong req->num_sgs value (The 2nd request doesn't use sg). For f_fs async io mode, it is not harm to initialize req->num_sgs as 0 either, in case, the UDC driver doesn't zeroed request structure.

Cc: Jun Li jun.li@nxp.com Cc: stable stable@vger.kernel.org Fixes: 772a7a724f69 ("usb: gadget: f_fs: Allow scatter-gather buffers") Signed-off-by: Peter Chen peter.chen@nxp.com

---

Changes for v2:

• Using the correct patch, and initialize req->num_sgs as 0 for aio too.

drivers/usb/gadget/function/f_fs.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index 59d9d512dcda..ced2581cf99f 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -1062,6 +1062,7 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data) req->num_sgs = io_data->sgt.nents; } else { req->buf = data;

•                   req->num_sgs = 0;
            }
            req->length = data_len;
  
  

@@ -1105,6 +1106,7 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data) req->num_sgs = io_data->sgt.nents; } else { req->buf = data;

•                   req->num_sgs = 0;
            }
            req->length = data_len;
  
  

-- 2.17.1

A gental ping...

Thanks, Peter