[Qemu-devel] [PATCH] ehci: Ensure that device is not NULL before calling usb_ep_get

[Guenter Roeck <linux@roeck-us.net>]

The following assert is seen once in a while while resetting the
Linux kernel.

qemu-system-x86_64: hw/usb/core.c:734: usb_ep_get:
	Assertion `dev != NULL' failed.

The call to usb_ep_get() originates from ehci_execute().
Analysis and debugging shows that p->queue->dev can indeed be NULL
in this function. Add check for this condition and return an error
if it is seen.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 hw/usb/hcd-ehci.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c
index 62dab05..c759f3e 100644
--- a/hw/usb/hcd-ehci.c
+++ b/hw/usb/hcd-ehci.c
@@ -1348,6 +1348,11 @@ static int ehci_execute(EHCIPacket *p, const char *action)
         return -1;
     }
 
+    if (p->queue->dev == NULL) {
+        ehci_trace_guest_bug(p->queue->ehci, "No device attached to queue\n");
+        return -1;
+    }
+
     if (get_field(p->qtd.token, QTD_TOKEN_TBYTES) > BUFF_SIZE) {
         ehci_trace_guest_bug(p->queue->ehci,
                              "guest requested more bytes than allowed");
-- 
2.7.4