linux-kernel - [PATCH 4.4 14/43] usb: gadget: f_midi: Fixed a bug when buflen was smaller than wMaxPacketSize

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Date:   Mon,  1 May 2017 14:27:14 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Michal Nazarewicz <mina86@...a86.com>,
        "Felipe F. Tonello" <eu@...ipetonello.com>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Julia Lawall <julia.lawall@...6.fr>
Subject: [PATCH 4.4 14/43] usb: gadget: f_midi: Fixed a bug when buflen was smaller than wMaxPacketSize

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Felipe F. Tonello <eu@...ipetonello.com>

commit 03d27ade4941076b34c823d63d91dc895731a595 upstream.

buflen by default (256) is smaller than wMaxPacketSize (512) in high-speed
devices.

That caused the OUT endpoint to freeze if the host send any data packet of
length greater than 256 bytes.

This is an example dump of what happended on that enpoint:
HOST:   [DATA][Length=260][...]
DEVICE: [NAK]
HOST:   [PING]
DEVICE: [NAK]
HOST:   [PING]
DEVICE: [NAK]
...
HOST:   [PING]
DEVICE: [NAK]

This patch fixes this problem by setting the minimum usb_request's buffer size
for the OUT endpoint as its wMaxPacketSize.

Acked-by: Michal Nazarewicz <mina86@...a86.com>
Signed-off-by: Felipe F. Tonello <eu@...ipetonello.com>
Signed-off-by: Felipe Balbi <felipe.balbi@...ux.intel.com>
Cc: Julia Lawall <julia.lawall@...6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/gadget/function/f_midi.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/usb/gadget/function/f_midi.c
+++ b/drivers/usb/gadget/function/f_midi.c
@@ -361,7 +361,9 @@ static int f_midi_set_alt(struct usb_fun
 	/* allocate a bunch of read buffers and queue them all at once. */
 	for (i = 0; i < midi->qlen && err == 0; i++) {
 		struct usb_request *req =
-			midi_alloc_ep_req(midi->out_ep, midi->buflen);
+			midi_alloc_ep_req(midi->out_ep,
+				max_t(unsigned, midi->buflen,
+					bulk_out_desc.wMaxPacketSize));
 		if (req == NULL)
 			return -ENOMEM;