USB: musb: host endpoint_disable() oops fixes

The musb_h_disable() routine can oops in some cases:

 - It's not safe to read hep->hcpriv outside musb->lock,
   since it gets changed on completion IRQ paths.

 - The list iterators aren't safe to use in that way;
   just remove the first element while !list_empty(),
   so deletions on other code paths can't make trouble.

We need two "scrub the list" loops because only one branch
should touch hardware and advance the schedule.

[ dbrownell@users.sourceforge.net: massively simplify
  patch description; add key points as code comments ]

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 26 insertions, 10 deletions

diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
index e32323938e98..c74ebadd4b9d 100644
--- a/drivers/usb/musb/musb_host.c
+++ b/drivers/usb/musb/musb_host.c
@@ -2103,15 +2103,16 @@ musb_h_disable(struct usb_hcd *hcd, struct usb_host_endpoint *hep)
         unsigned long           flags;
         struct musb             *musb = hcd_to_musb(hcd);
         u8                      is_in = epnum & USB_DIR_IN;
-        struct musb_qh          *qh = hep->hcpriv;
-        struct urb              *urb, *tmp;
+        struct musb_qh          *qh;
+        struct urb              *urb;
         struct list_head        *sched;
 
-        if (!qh)
-                return;
-
         spin_lock_irqsave(&musb->lock, flags);
 
+        qh = hep->hcpriv;
+        if (qh == NULL)
+                goto exit;
+
         switch (qh->type) {
         case USB_ENDPOINT_XFER_CONTROL:
                 sched = &musb->control;
@@ -2145,13 +2146,28 @@ musb_h_disable(struct usb_hcd *hcd, struct usb_host_endpoint *hep)
 
                 /* cleanup */
                 musb_cleanup_urb(urb, qh, urb->pipe & USB_DIR_IN);
-        } else
-                urb = NULL;
 
-        /* then just nuke all the others */
-        list_for_each_entry_safe_from(urb, tmp, &hep->urb_list, urb_list)
-                musb_giveback(qh, urb, -ESHUTDOWN);
+                /* Then nuke all the others ... and advance the
+                 * queue on hw_ep (e.g. bulk ring) when we're done.
+                 */
+                while (!list_empty(&hep->urb_list)) {
+                        urb = next_urb(qh);
+                        urb->status = -ESHUTDOWN;
+                        musb_advance_schedule(musb, urb, qh->hw_ep, is_in);
+                }
+        } else {
+                /* Just empty the queue; the hardware is busy with
+                 * other transfers, and since !qh->is_ready nothing
+                 * will activate any of these as it advances.
+                 */
+                while (!list_empty(&hep->urb_list))
+                        __musb_giveback(musb, next_urb(qh), -ESHUTDOWN);
 
+                hep->hcpriv = NULL;
+                list_del(&qh->ring);
+                kfree(qh);
+        }
+exit:
         spin_unlock_irqrestore(&musb->lock, flags);
 }