usbhid: prevent deadlock during timeout
Oliver Neukum [Mon, 30 Apr 2012 07:13:46 +0000 (09:13 +0200)]
commit 8815bb09af21316aeb5f8948b24ac62181670db2 upstream.

On some HCDs usb_unlink_urb() can directly call the
completion handler. That limits the spinlocks that can
be taken in the handler to locks not held while calling
usb_unlink_urb()
To prevent a race with resubmission, this patch exposes
usbcore's infrastructure for blocking submission, uses it
and so drops the lock without causing a race in usbhid.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hid/usbhid/hid-core.c
drivers/usb/core/urb.c
include/linux/usb.h

index 5bf91db..4bbb883 100644 (file)
@@ -399,6 +399,16 @@ static int hid_submit_ctrl(struct hid_device *hid)
  * Output interrupt completion handler.
  */
 
+static int irq_out_pump_restart(struct hid_device *hid)
+{
+       struct usbhid_device *usbhid = hid->driver_data;
+
+       if (usbhid->outhead != usbhid->outtail)
+               return hid_submit_out(hid);
+       else
+               return -1;
+}
+
 static void hid_irq_out(struct urb *urb)
 {
        struct hid_device *hid = urb->context;
@@ -428,7 +438,7 @@ static void hid_irq_out(struct urb *urb)
        else
                usbhid->outtail = (usbhid->outtail + 1) & (HID_OUTPUT_FIFO_SIZE - 1);
 
-       if (usbhid->outhead != usbhid->outtail && !hid_submit_out(hid)) {
+       if (!irq_out_pump_restart(hid)) {
                /* Successfully submitted next urb in queue */
                spin_unlock_irqrestore(&usbhid->lock, flags);
                return;
@@ -443,6 +453,15 @@ static void hid_irq_out(struct urb *urb)
 /*
  * Control pipe completion handler.
  */
+static int ctrl_pump_restart(struct hid_device *hid)
+{
+       struct usbhid_device *usbhid = hid->driver_data;
+
+       if (usbhid->ctrlhead != usbhid->ctrltail)
+               return hid_submit_ctrl(hid);
+       else
+               return -1;
+}
 
 static void hid_ctrl(struct urb *urb)
 {
@@ -476,7 +495,7 @@ static void hid_ctrl(struct urb *urb)
        else
                usbhid->ctrltail = (usbhid->ctrltail + 1) & (HID_CONTROL_FIFO_SIZE - 1);
 
-       if (usbhid->ctrlhead != usbhid->ctrltail && !hid_submit_ctrl(hid)) {
+       if (!ctrl_pump_restart(hid)) {
                /* Successfully submitted next urb in queue */
                spin_unlock(&usbhid->lock);
                return;
@@ -535,11 +554,27 @@ static void __usbhid_submit_report(struct hid_device *hid, struct hid_report *re
                         * the queue is known to run
                         * but an earlier request may be stuck
                         * we may need to time out
-                        * no race because this is called under
+                        * no race because the URB is blocked under
                         * spinlock
                         */
-                       if (time_after(jiffies, usbhid->last_out + HZ * 5))
+                       if (time_after(jiffies, usbhid->last_out + HZ * 5)) {
+                               usb_block_urb(usbhid->urbout);
+                               /* drop lock to not deadlock if the callback is called */
+                               spin_unlock(&usbhid->lock);
                                usb_unlink_urb(usbhid->urbout);
+                               spin_lock(&usbhid->lock);
+                               usb_unblock_urb(usbhid->urbout);
+                               /*
+                                * if the unlinking has already completed
+                                * the pump will have been stopped
+                                * it must be restarted now
+                                */
+                               if (!test_bit(HID_OUT_RUNNING, &usbhid->iofl))
+                                       if (!irq_out_pump_restart(hid))
+                                               set_bit(HID_OUT_RUNNING, &usbhid->iofl);
+
+
+                       }
                }
                return;
        }
@@ -583,11 +618,25 @@ static void __usbhid_submit_report(struct hid_device *hid, struct hid_report *re
                 * the queue is known to run
                 * but an earlier request may be stuck
                 * we may need to time out
-                * no race because this is called under
+                * no race because the URB is blocked under
                 * spinlock
                 */
-               if (time_after(jiffies, usbhid->last_ctrl + HZ * 5))
+               if (time_after(jiffies, usbhid->last_ctrl + HZ * 5)) {
+                       usb_block_urb(usbhid->urbctrl);
+                       /* drop lock to not deadlock if the callback is called */
+                       spin_unlock(&usbhid->lock);
                        usb_unlink_urb(usbhid->urbctrl);
+                       spin_lock(&usbhid->lock);
+                       usb_unblock_urb(usbhid->urbctrl);
+                       /*
+                        * if the unlinking has already completed
+                        * the pump will have been stopped
+                        * it must be restarted now
+                        */
+                       if (!test_bit(HID_CTRL_RUNNING, &usbhid->iofl))
+                               if (!ctrl_pump_restart(hid))
+                                       set_bit(HID_CTRL_RUNNING, &usbhid->iofl);
+               }
        }
 }
 
index cd9b3a2..9d912bf 100644 (file)
@@ -681,6 +681,27 @@ void usb_unpoison_urb(struct urb *urb)
 EXPORT_SYMBOL_GPL(usb_unpoison_urb);
 
 /**
+ * usb_block_urb - reliably prevent further use of an URB
+ * @urb: pointer to URB to be blocked, may be NULL
+ *
+ * After the routine has run, attempts to resubmit the URB will fail
+ * with error -EPERM.  Thus even if the URB's completion handler always
+ * tries to resubmit, it will not succeed and the URB will become idle.
+ *
+ * The URB must not be deallocated while this routine is running.  In
+ * particular, when a driver calls this routine, it must insure that the
+ * completion handler cannot deallocate the URB.
+ */
+void usb_block_urb(struct urb *urb)
+{
+       if (!urb)
+               return;
+
+       atomic_inc(&urb->reject);
+}
+EXPORT_SYMBOL_GPL(usb_block_urb);
+
+/**
  * usb_kill_anchored_urbs - cancel transfer requests en masse
  * @anchor: anchor the requests are bound to
  *
index 73b68d1..26229fd 100644 (file)
@@ -1379,6 +1379,7 @@ extern int usb_unlink_urb(struct urb *urb);
 extern void usb_kill_urb(struct urb *urb);
 extern void usb_poison_urb(struct urb *urb);
 extern void usb_unpoison_urb(struct urb *urb);
+extern void usb_block_urb(struct urb *urb);
 extern void usb_kill_anchored_urbs(struct usb_anchor *anchor);
 extern void usb_poison_anchored_urbs(struct usb_anchor *anchor);
 extern void usb_unpoison_anchored_urbs(struct usb_anchor *anchor);
@@ -1391,6 +1392,8 @@ extern struct urb *usb_get_from_anchor(struct usb_anchor *anchor);
 extern void usb_scuttle_anchored_urbs(struct usb_anchor *anchor);
 extern int usb_anchor_empty(struct usb_anchor *anchor);
 
+#define usb_unblock_urb        usb_unpoison_urb
+
 /**
  * usb_urb_dir_in - check if an URB describes an IN transfer
  * @urb: URB to be checked