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Subject: Re: [PATCH] xen/privcmd: allow fetching resource sizes
To:     Roger Pau Monne <roger.pau@citrix.com>,
        linux-kernel@vger.kernel.org
Cc:     Juergen Gross <jgross@suse.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Paul Durrant <paul.durrant@citrix.com>,
        xen-devel@lists.xenproject.org
References: <20210111152958.7166-1-roger.pau@citrix.com>
From:   boris.ostrovsky@oracle.com
Organization: Oracle Corporation
Message-ID: <555ba53c-1b6b-6cf7-9887-52d4179f7456@oracle.com>
Date:   Mon, 11 Jan 2021 17:09:54 -0500
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On 1/11/21 10:29 AM, Roger Pau Monne wrote:
>  
> +	xdata.domid = kdata.dom;
> +	xdata.type = kdata.type;
> +	xdata.id = kdata.id;
> +
> +	if (!kdata.addr && !kdata.num) {


I think we should not allow only one of them to be zero. If it's only kdata.num then we will end up with pfns array set to ZERO_SIZE_PTR (which is 0x10). We seem to be OK in that we are not derefencing pfns (either in kernel or in hypervisor) if number of frames is zero but IMO we shouldn't be tempting the fate.


(And if it's only kdata.addr then we will get a vma but I am not sure it will do what we want.)


-boris