[PATCH v2 2/2] hw: usb: hcd-ohci: check for processed TD before retire

[P J P <ppandit@redhat.com>]

From: Prasad J Pandit <pjp@fedoraproject.org>

While servicing OHCI transfer descriptors(TD), ohci_service_iso_td
retires a TD if it has passed its time frame. It does not check if
the TD was already processed once and holds an error code in TD_CC.
It may happen if the TD list has a loop. Add check to avoid an
infinite loop condition.

Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/usb/hcd-ohci.c | 4 ++++
 1 file changed, 4 insertions(+)

Update v2: one patch for loop issue
  -> https://lists.nongnu.org/archive/html/qemu-devel/2020-09/msg05145.html

diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c
index 9dc59101f9..8b912e95d3 100644
--- a/hw/usb/hcd-ohci.c
+++ b/hw/usb/hcd-ohci.c
@@ -691,6 +691,10 @@ static int ohci_service_iso_td(OHCIState *ohci, struct ohci_ed *ed,
            the next ISO TD of the same ED */
         trace_usb_ohci_iso_td_relative_frame_number_big(relative_frame_number,
                                                         frame_count);
+        if (OHCI_CC_DATAOVERRUN == OHCI_BM(iso_td.flags, TD_CC)) {
+            /* avoid infinite loop */
+            return 1;
+        }
         OHCI_SET_BM(iso_td.flags, TD_CC, OHCI_CC_DATAOVERRUN);
         ed->head &= ~OHCI_DPTR_MASK;
         ed->head |= (iso_td.next & OHCI_DPTR_MASK);
-- 
2.26.2