[PATCH v2] usb: musb: Fix musb_gadget.c rxstate overflow bug

[Robin Guo <guoweibin@inspur.com>]

The usb function device call musb_gadget_queue() adds the passed
request to musb_ep::req_list,If the (request->length > musb_ep->packet_sz)
and (is_buffer_mapped(req) return false),the rxstate() will copy all data
in fifo to request->buf which may cause request->buf out of bounds.

Fix it by add the length check :
fifocnt = min_t(unsigned, request->length - request->actual, fifocnt);

Signed-off-by: Robin Guo <guoweibin@inspur.com>
---
Changelog:

v1 -> v2:

1. Change the email name
2. Modify the commit log
---
 drivers/usb/musb/musb_gadget.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index 51274b87f46c..dc67fff8e941 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -760,6 +760,9 @@ static void rxstate(struct musb *musb, struct musb_request *req)
 			musb_writew(epio, MUSB_RXCSR, csr);
 
 buffer_aint_mapped:
+			fifo_count = min_t(unsigned int,
+					request->length - request->actual,
+					(unsigned int)fifo_count);
 			musb_read_fifo(musb_ep->hw_ep, fifo_count, (u8 *)
 					(request->buf + request->actual));
 			request->actual += fifo_count;
-- 
2.17.1