xhci fixes for usb-linus

Hi Greg

One patch for usb-linus that fixes the audio sideband crash Lianqin recently found during suspend/resume testing

Thanks
Mathias

Mathias Nyman (1):
xhci: sideband: don't dereference freed ring when removing sideband
endpoint

 drivers/usb/host/xhci-sideband.c |  1 -
 drivers/usb/host/xhci.c          | 15 ++++++++++++---
 2 files changed, 12 insertions(+), 4 deletions(-)

2.43.0

xhci_sideband_remove_endpoint() incorrecly assumes that the endpoint is running and has a valid transfer ring.

Lianqin reported a crash during suspend/wake-up stress testing, and found the cause to be dereferencing a non-existing transfer ring 'ep->ring' during xhci_sideband_remove_endpoint().

The endpoint and its ring may be in unknown state if this function is called after xHCI was reinitialized in resume (lost power), or if device is being re-enumerated, disconnected or endpoint already dropped.

Fix this by both removing unnecessary ring access, and by checking ep->ring exists before dereferencing it. Also make sure endpoint is running before attempting to stop it.

Remove the xhci_initialize_ring_info() call during sideband endpoint removal as is it only initializes ring structure enqueue, dequeue and cycle state values to their starting values without changing actual hardware enqueue, dequeue and cycle state. Leaving them out of sync is worse than leaving it as it is. The endpoint will get freed in after this in most usecases.

If the (audio) class driver want's to reuse the endpoint after offload then it is up to the class driver to ensure endpoint is properly set up.

---
 drivers/usb/host/xhci-sideband.c |  1 -
 drivers/usb/host/xhci.c          | 15 ++++++++++++---
 2 files changed, 12 insertions(+), 4 deletions(-)

index a85f62a73313..2bd77255032b 100644
@@ -210,7 +210,6 @@ xhci_sideband_remove_endpoint(struct xhci_sideband *sb,
 		return -ENODEV;
 
 	__xhci_sideband_remove_endpoint(sb, ep);
-	xhci_initialize_ring_info(ep->ring);
 
 	return 0;
 }

index 02c9bfe21ae2..b3ba16b9718c 100644
@@ -2898,16 +2898,25 @@ int xhci_stop_endpoint_sync(struct xhci_hcd *xhci, struct xhci_virt_ep *ep, int
 			    gfp_t gfp_flags)
 {
 	struct xhci_command *command;
+	struct xhci_ep_ctx *ep_ctx;
 	unsigned long flags;
-	int ret;
+	int ret = -ENODEV;
 
 	command = xhci_alloc_command(xhci, true, gfp_flags);
 	if (!command)
 		return -ENOMEM;
 
 	spin_lock_irqsave(&xhci->lock, flags);
-	ret = xhci_queue_stop_endpoint(xhci, command, ep->vdev->slot_id,
-				       ep->ep_index, suspend);
+
+	/* make sure endpoint exists and is running before stopping it */
+	if (ep->ring) {
+		ep_ctx = xhci_get_ep_ctx(xhci, ep->vdev->out_ctx, ep->ep_index);
+		if (GET_EP_CTX_STATE(ep_ctx) == EP_STATE_RUNNING)
+			ret = xhci_queue_stop_endpoint(xhci, command,
+						       ep->vdev->slot_id,
+						       ep->ep_index, suspend);
+	}
+
 	if (ret < 0) {
 		spin_unlock_irqrestore(&xhci->lock, flags);
 		goto out;

2.43.0