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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jun Li <jun.li@nxp.com>,
        Peter Chen <peter.chen@nxp.com>,
        Felipe Balbi <balbi@kernel.org>
Subject: [PATCH 5.5 047/367] usb: gadget: f_fs: set req->num_sgs as 0 for non-sg transfer
Date:   Mon, 10 Feb 2020 04:29:20 -0800
Message-Id: <20200210122428.383827294@linuxfoundation.org>
In-Reply-To: <20200210122423.695146547@linuxfoundation.org>
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From: Peter Chen <peter.chen@nxp.com>

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>

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

--- 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
 			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
 			req->num_sgs = io_data->sgt.nents;
 		} else {
 			req->buf = data;
+			req->num_sgs = 0;
 		}
 		req->length = data_len;