Re: [Xen-devel] [PATCH v5 26/28] xsplice: Prevent duplicate payloads from being loaded.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.03.16 at 21:00, <konrad.wilk@xxxxxxxxxx> wrote:
> --- a/xen/common/xsplice.c
> +++ b/xen/common/xsplice.c
> @@ -566,6 +566,27 @@ static int prepare_payload(struct payload *payload,
>          if ( !payload->id.len || !payload->id.p )
>              return -EINVAL;
>      }
> +    /* Make sure it is not a duplicate. */
> +    if ( payload->id.len )

The conditional is pointless considering the one visible in context
above.

> +    {
> +        struct payload *data;
> +
> +        spin_lock_recursive(&payload_lock);
> +        list_for_each_entry ( data, &payload_list, list )
> +        {
> +            /* No way payload is on the list. */
> +            ASSERT( data != payload );
> +            if ( data->id.len &&
> +                 !memcmp(data->id.p, payload->id.p, data->id.len) )
> +            {
> +                spin_unlock_recursive(&payload_lock);
> +                dprintk(XENLOG_DEBUG, "%s%s: Already loaded as %s!\n",
> +                        XSPLICE, elf->name, data->name);
> +                return -EEXIST;
> +            }
> +        }
> +        spin_unlock_recursive(&payload_lock);

Similar question as asked elsewhere - with the lock getting dropped
here, how is the "no duplicate" state going to be ensured by the
time you actually load and insert this payload?

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel