RE: Null-pointer access in netback_uevent

["James Harper" <james.harper@bendigoit.com.au>]

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Check if drvdata has been set up yet and return if it hasn't

Signed-off-by: James Harper <james.harper@bendigoit.com.au>
---
 drivers/xen/netback/xenbus.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/netback/xenbus.c b/drivers/xen/netback/xenbus.c
index 70636d0..a46d8b2 100644
--- a/drivers/xen/netback/xenbus.c
+++ b/drivers/xen/netback/xenbus.c
@@ -162,12 +162,16 @@ fail:
  */
 static int netback_uevent(struct xenbus_device *xdev, struct kobj_uevent_env *env)
 {
-       struct backend_info *be = dev_get_drvdata(&xdev->dev);
-       struct xen_netif *netif = be->netif;
+       struct backend_info *be;
+       struct xen_netif *netif;
        char *val;

        DPRINTK("netback_uevent");

+       be = dev_get_drvdata(&xdev->dev);
+       if (!be)
+               return 0;
+       netif = be->netif;
        val = xenbus_read(XBT_NIL, xdev->nodename, "script", NULL);
        if (IS_ERR(val)) {
                int err = PTR_ERR(val);
--
1.7.1


> -----Original Message-----
> From: Jeremy Fitzhardinge [mailto:jeremy@goop.org]
> Sent: Saturday, 29 May 2010 09:31
> To: James Harper
> Cc: Bastian Blank; xen-devel@lists.xensource.com
> Subject: Re: [Xen-devel] Null-pointer access in netback_uevent
> 
> On 05/28/2010 03:42 PM, James Harper wrote:
> >>>> Looking into this further, I suspect that the trigger here is a newer
> >>>> version of udev or something in that area. netback_uevent is getting
> called
> >>>> before the call to netback_probe containing the call to dev_set_drvdata.
> >>>>
> >>>>
> >>> There are two problems there. And yes, the uevent routine can be called
> >>> at any time.
> >>>
> >>>
> >> So would it be correct for it to just return if either of those are
> >> NULL?
> >>
> > Not sure. It works though.
> >
> 
> Can you send me a properly signed-off patch?
> 
> Thanks,
>     J

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