usb: gadget: loopback: don't queue requests to bogus endpoints

A request allocated from e.g. ep1out cannot
be queued to any other endpoint. This bug has
been in f_loopback at least since mid-2011 and
since nobody has really screamed about it, we're
not backporting to any stable kernels.

Debugged with MUSB since that's the only controller
which complains about this case.

Signed-off-by: Felipe Balbi <balbi@ti.com>

1 files changed, 42 insertions, 45 deletions

diff --git a/drivers/usb/gadget/function/f_loopback.c b/drivers/usb/gadget/function/f_loopback.c
index bf04389137e6..298b46112b1a 100644
--- a/drivers/usb/gadget/function/f_loopback.c
+++ b/drivers/usb/gadget/function/f_loopback.c
@@ -253,22 +253,13 @@ static void loopback_complete(struct usb_ep *ep, struct usb_request *req)
 
         case 0:                         /* normal completion? */
                 if (ep == loop->out_ep) {
-                        /* loop this OUT packet back IN to the host */
                         req->zero = (req->actual < req->length);
                         req->length = req->actual;
-                        status = usb_ep_queue(loop->in_ep, req, GFP_ATOMIC);
-                        if (status == 0)
-                                return;
-
-                        /* "should never get here" */
-                        ERROR(cdev, "can't loop %s to %s: %d\n",
-                                ep->name, loop->in_ep->name,
-                                status);
                 }
 
                 /* queue the buffer for some later OUT packet */
                 req->length = buflen;
-                status = usb_ep_queue(loop->out_ep, req, GFP_ATOMIC);
+                status = usb_ep_queue(ep, req, GFP_ATOMIC);
                 if (status == 0)
                         return;
 
@@ -308,60 +299,66 @@ static inline struct usb_request *lb_alloc_ep_req(struct usb_ep *ep, int len)
         return alloc_ep_req(ep, len, buflen);
 }
 
-static int
-enable_loopback(struct usb_composite_dev *cdev, struct f_loopback *loop)
+static int enable_endpoint(struct usb_composite_dev *cdev, struct f_loopback *loop,
+                struct usb_ep *ep)
 {
-        int                                     result = 0;
-        struct usb_ep                           *ep;
         struct usb_request                      *req;
         unsigned                                i;
+        int                                     result;
 
-        /* one endpoint writes data back IN to the host */
-        ep = loop->in_ep;
+        /*
+         * one endpoint writes data back IN to the host while another endpoint
+         * just reads OUT packets
+         */
         result = config_ep_by_speed(cdev->gadget, &(loop->function), ep);
         if (result)
-                return result;
+                goto fail0;
         result = usb_ep_enable(ep);
         if (result < 0)
-                return result;
-        ep->driver_data = loop;
-
-        /* one endpoint just reads OUT packets */
-        ep = loop->out_ep;
-        result = config_ep_by_speed(cdev->gadget, &(loop->function), ep);
-        if (result)
                 goto fail0;
-
-        result = usb_ep_enable(ep);
-        if (result < 0) {
-fail0:
-                ep = loop->in_ep;
-                usb_ep_disable(ep);
-                ep->driver_data = NULL;
-                return result;
-        }
         ep->driver_data = loop;
 
-        /* allocate a bunch of read buffers and queue them all at once.
+        /*
+         * allocate a bunch of read buffers and queue them all at once.
          * we buffer at most 'qlen' transfers; fewer if any need more
          * than 'buflen' bytes each.
          */
         for (i = 0; i < qlen && result == 0; i++) {
                 req = lb_alloc_ep_req(ep, 0);
-                if (req) {
-                        req->complete = loopback_complete;
-                        result = usb_ep_queue(ep, req, GFP_ATOMIC);
-                        if (result)
-                                ERROR(cdev, "%s queue req --> %d\n",
-                                                ep->name, result);
-                } else {
-                        usb_ep_disable(ep);
-                        ep->driver_data = NULL;
-                        result = -ENOMEM;
-                        goto fail0;
+                if (!req)
+                        goto fail1;
+
+                req->complete = loopback_complete;
+                result = usb_ep_queue(ep, req, GFP_ATOMIC);
+                if (result) {
+                        ERROR(cdev, "%s queue req --> %d\n",
+                                        ep->name, result);
+                        goto fail1;
                 }
         }
 
+        return 0;
+
+fail1:
+        usb_ep_disable(ep);
+
+fail0:
+        return result;
+}
+
+static int
+enable_loopback(struct usb_composite_dev *cdev, struct f_loopback *loop)
+{
+        int                                     result = 0;
+
+        result = enable_endpoint(cdev, loop, loop->in_ep);
+        if (result)
+                return result;
+
+        result = enable_endpoint(cdev, loop, loop->out_ep);
+        if (result)
+                return result;
+
         DBG(cdev, "%s enabled\n", loop->function.name);
         return result;
 }