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

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 7/30/19 7:45 PM, Guenter Roeck wrote:
> 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.

Your patch is not wrong as it corrects your case, but I wonder why we
get there. This assert seems to have catched a bug.

Gerd, shouldn't we call usb_packet_cleanup() in ehci_reset() rather than
ehci_finalize()? Then we shouldn't need this patch.

> 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");
>