Re: [Xen-devel] [PATCH] xen: Add RING_COPY_RESPONSE()

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Apr 30, 2018 at 11:54:36PM +0200, Marek Marczykowski-Górecki wrote:
> Using RING_GET_RESPONSE() on a shared ring is easy to use incorrectly
> (i.e., by not considering that the other end may alter the data in the
> shared ring while it is being inspected).  Safe usage of a response
> generally requires taking a local copy.
> 
> Provide a RING_COPY_RESPONSE() macro to use instead of
> RING_GET_RESPONSE() and an open-coded memcpy().  This takes care of
> ensuring that the copy is done correctly regardless of any possible
> compiler optimizations.
> 
> Use a volatile source to prevent the compiler from reordering or
> omitting the copy.
> 
> This is complementary to XSA155.
> 
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>

Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>

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