release/5.2.39/usb-gadget-f_fs-set-req-num_sgs-as-0-for-non-sg-tran.patch

From 631ae1f3155eff19e29e2254098054cf776b1df1 Mon Sep 17 00:00:00 2001
From: Peter Chen <peter.chen@nxp.com>
Date: Thu, 12 Dec 2019 16:35:03 +0800
Subject: [PATCH] usb: gadget: f_fs: set req->num_sgs as 0 for non-sg transfer

commit d2450c6937018d40d4111fe830fa48d4ddceb8d0 upstream.

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>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 213ff03c8a9f..9a4707a934a6 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -1061,6 +1061,7 @@ 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;
 
@@ -1104,6 +1105,7 @@ 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;
 
-- 
2.7.4