Re: [Xen-devel] [PATCH 1/3] xen/blkback: Don't trust the handle from the frontend.

Jan Beulich
2013-01-28T11:09:22Z

>>> On 25.01.13 at 18:32, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
> The 'handle' is the device that the request is from. For the life-time
> of the ring we copy it from a request to a response so that the frontend
> is not surprised by it. But we do not need it - when we start processing
> I/Os we have our own 'struct phys_req' which has only most essential
> information about the request. In fact the 'vbd_translate' ends up
> over-writing the preq.dev with a value from the backend.
>
> This assignment of preq.dev with the 'handle' value is superfluous
> so lets not do it.
>
> Cc: stable@vger.kernel.org

Is this really stable material? It fixes nothing but the (wrong)
impression that the driver might be using frontend provided data
without checking.

Jan

> Acked-by: Jan Beulich <jbeulich@suse.com>
> Acked-by: Ian Campbell <ian.campbell@citrix.com>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
> drivers/block/xen-blkback/blkback.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/drivers/block/xen-blkback/blkback.c
> b/drivers/block/xen-blkback/blkback.c
> index 742871d..2de3da9 100644
> --- a/drivers/block/xen-blkback/blkback.c
> +++ b/drivers/block/xen-blkback/blkback.c
> @@ -890,7 +890,6 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
> goto fail_response;
> }
>
> - preq.dev = req->u.rw.handle;
> preq.sector_number = req->u.rw.sector_number;
> preq.nr_sects = 0;
>
> --
> 1.8.0.2
>
>
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