Re: [Xen-devel] [PATCH 7/9] xen/xenbus: Check before dereferencing it.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2011-09-29 at 20:52 +0100, Konrad Rzeszutek Wilk wrote:
> . we do the check whether 'xdev' is NULL - but after we have
> dereferenced it.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
>  drivers/xen/xenbus/xenbus_probe_backend.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/xen/xenbus/xenbus_probe_backend.c 
> b/drivers/xen/xenbus/xenbus_probe_backend.c
> index 60adf91..331589a 100644
> --- a/drivers/xen/xenbus/xenbus_probe_backend.c
> +++ b/drivers/xen/xenbus/xenbus_probe_backend.c
> @@ -103,10 +103,11 @@ static int xenbus_uevent_backend(struct device *dev,
>               return -ENODEV;
>  
>       xdev = to_xenbus_device(dev);

to_xenbus_device is just container_of. The only way it would return NULL
is if dev == offsetof(struct xenbus_device, dev), which isn't terribly
likely. A more likely error would be dev == NULL and we just checked
above.

> -     bus = container_of(xdev->dev.bus, struct xen_bus_type, bus);
>       if (xdev == NULL)
>               return -ENODEV;
>  
> +     bus = container_of(xdev->dev.bus, struct xen_bus_type, bus);
> +
>       if (add_uevent_var(env, "MODALIAS=xen-backend:%s", xdev->devicetype))
>               return -ENOMEM;
>  



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