Re: [Qemu-devel] [PATCH 9/9] hcd-musb: fix dereference null return value

[Paolo Bonzini]

On 15/11/2014 11:06, arei.gong...@huawei.com wrote:
> From: Gonglei <arei.gong...@huawei.com>
> 
> Signed-off-by: Gonglei <arei.gong...@huawei.com>
> ---
>  hw/usb/hcd-musb.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/hw/usb/hcd-musb.c b/hw/usb/hcd-musb.c
> index 66bc61a..f2cb73c 100644
> --- a/hw/usb/hcd-musb.c
> +++ b/hw/usb/hcd-musb.c
> @@ -624,6 +624,10 @@ static void musb_packet(MUSBState *s, MUSBEndPoint *ep,
>  
>      /* A wild guess on the FADDR semantics... */
>      dev = usb_find_device(&s->port, ep->faddr[idx]);
> +    if (!dev) {
> +        TRACE("Do not find an usb device");
> +        return;
> +    }
>      uep = usb_ep_get(dev, pid, ep->type[idx] & 0xf);
>      usb_packet_setup(&ep->packey[dir].p, pid, uep, 0,
>                       (dev->addr << 16) | (uep->nr << 8) | pid, false, true);
> 

I think this patch is not the real fix.  usb_ep_get and
usb_handle_packet can deal with a NULL device, but we have to avoid 
dereferencing NULL pointers when building the id.

Paolo

diff --git a/hw/usb/hcd-musb.c b/hw/usb/hcd-musb.c
index 66bc61a..40809f6 100644
--- a/hw/usb/hcd-musb.c
+++ b/hw/usb/hcd-musb.c
@@ -608,6 +608,7 @@ static void musb_packet(MUSBState *s, MUSBEndPoint *ep,
     USBDevice *dev;
     USBEndpoint *uep;
     int idx = epnum && dir;
+    int id;
     int ttype;
 
     /* ep->type[0,1] contains:
@@ -625,8 +626,11 @@ static void musb_packet(MUSBState *s, MUSBEndPoint *ep,
     /* A wild guess on the FADDR semantics... */
     dev = usb_find_device(&s->port, ep->faddr[idx]);
     uep = usb_ep_get(dev, pid, ep->type[idx] & 0xf);
-    usb_packet_setup(&ep->packey[dir].p, pid, uep, 0,
-                     (dev->addr << 16) | (uep->nr << 8) | pid, false, true);
+    id = pid;
+    if (uep) {
+        id |= (dev->addr << 16) | (uep->nr << 8);
+    }
+    usb_packet_setup(&ep->packey[dir].p, pid, uep, 0, id, false, true);
     usb_packet_addbuf(&ep->packey[dir].p, ep->buf[idx], len);
     ep->packey[dir].ep = ep;
     ep->packey[dir].dir = dir;