Message-ID: <6141d292-692d-9828-48c1-2d00e0285903@oracle.com>
Date:   Fri, 19 Nov 2021 17:32:15 -0500
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Subject: Re: [PATCH v2] xen: detect uninitialized xenbus in xenbus_init
Content-Language: en-US
To:     Stefano Stabellini <sstabellini@kernel.org>, jgross@suse.com
Cc:     xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org,
        jbeulich@suse.com,
        Stefano Stabellini <stefano.stabellini@xilinx.com>,
        stable@vger.kernel.org
References: <20211119202951.403525-1-sstabellini@kernel.org>
From:   Boris Ostrovsky <boris.ostrovsky@oracle.com>
In-Reply-To: <20211119202951.403525-1-sstabellini@kernel.org>
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On 11/19/21 3:29 PM, Stefano Stabellini wrote:
> From: Stefano Stabellini <stefano.stabellini@xilinx.com>
>
> If the xenstore page hasn't been allocated properly, reading the value
> of the related hvm_param (HVM_PARAM_STORE_PFN) won't actually return
> error. Instead, it will succeed and return zero. Instead of attempting
> to xen_remap a bad guest physical address, detect this condition and
> return early.
>
> Note that although a guest physical address of zero for
> HVM_PARAM_STORE_PFN is theoretically possible, it is not a good choice
> and zero has never been validly used in that capacity.
>
> Also recognize the invalid value of INVALID_PFN which is ULLONG_MAX.
>
> For 32-bit Linux, any pfn above ULONG_MAX would get truncated. Pfns
> above ULONG_MAX should never be passed by the Xen tools to HVM guests
> anyway, so check for this condition and return early.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>


Reviewed-by: Boris Ostrovsky <boris.ostrvsky@oracle.com>