usb: gadget: f_fs: Only return delayed status when len is 0

commit 4d644abf25698362bd33d17c9ddc8f7122c30f17 upstream.

Commit 1b9ba000 ("Allow function drivers to pause control
transfers") states that USB_GADGET_DELAYED_STATUS is only
supported if data phase is 0 bytes.

It seems that when the length is not 0 bytes, there is no
need to explicitly delay the data stage since the transfer
is not completed until the user responds. However, when the
length is 0, there is no data stage and the transfer is
finished once setup() returns, hence there is a need to
explicitly delay completion.

This manifests as the following bugs:

Prior to 946ef68ad4e4 ('Let setup() return
USB_GADGET_DELAYED_STATUS'), when setup is 0 bytes, ffs
would require user to queue a 0 byte request in order to
clear setup state. However, that 0 byte request was actually
not needed and would hang and cause errors in other setup
requests.

After the above commit, 0 byte setups work since the gadget
now accepts empty queues to ep0 to clear the delay, but all
other setups hang.

Fixes: 946ef68ad4e4 ("Let setup() return USB_GADGET_DELAYED_STATUS")
Signed-off-by: Jerry Zhang <zhangjerry@google.com>
Cc: stable <stable@vger.kernel.org>
Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[dwoo08.lee: cherry-pick linux-4.9.y stable commit 9e10043b6bdc to stablize f_fs]
Signed-off-by: Dongwoo Lee <dwoo08.lee@samsung.com>
Change-Id: Idf5d504bd5059cc5141f4a3e98c572708c631079

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index da7a4865b361966de743ad78c8b40d770045b455..a29dfe848c4ce7746e935f78f6a2946f9b8984a5 100644 (file)
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -3254,7 +3254,7 @@ static int ffs_func_setup(struct usb_function *f,
        __ffs_event_add(ffs, FUNCTIONFS_SETUP);
        spin_unlock_irqrestore(&ffs->ev.waitq.lock, flags);
 
-       return USB_GADGET_DELAYED_STATUS;
+       return creq->wLength == 0 ? USB_GADGET_DELAYED_STATUS : 0;
 }
 
 static bool ffs_func_req_match(struct usb_function *f,