Re: [Xen-devel] [PATCH v2 4/6] x86/xstate: Fix latent bugs in expand_xsave_states()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.09.16 at 18:21, <andrew.cooper3@xxxxxxxxxx> wrote:
> Without checking the size input, the memcpy() for the uncompressed path might
> read off the end of the vcpu's xsave_area.  Both callers pass the approprite
> size, so hold them to it with a BUG_ON().
> 
> The compressed path is currently dead code, but its attempt to avoid leaking
> uninitalised data was incomplete.  Work around this by zeroing the whole rest
> of the buffer before decompression.
> 
> The loop skips all bits which aren't set in xstate_bv, meaning that the
> memset() was dead code.  The logic is more obvious with get_xsave_addr()
> expanded inline, allowing for quite a lot of simplification, including all the
> NULL pointer logic.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <JBeulich@xxxxxxxx>
with one suggestion:

>  void expand_xsave_states(struct vcpu *v, void *dest, unsigned int size)
>  {
>      struct xsave_struct *xsave = v->arch.xsave_area;
> +    const void *src;

I think with the addition of this variable and the removal of the use of
get_xsave_addr() "xsave" can now also be const.

Jan


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