[PATCH v2 1/1] usb: gadget: f_fs: set req->num_sgs as 0 for non-sg transfer

[Peter Chen <peter.chen@xxxxxxx>]

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@xxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Fixes: 772a7a724f69 ("usb: gadget: f_fs: Allow scatter-gather buffers")
Signed-off-by: Peter Chen <peter.chen@xxxxxxx>
---
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