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Re: [Xen-devel] [PATCH 21/22] libxc: range checks in xc_dom_p2m_host and _guest

On 12/06/13 17:06, Ian Jackson wrote:
George Dunlap writes ("Re: [Xen-devel] [PATCH 21/22] libxc: range checks in 
xc_dom_p2m_host and _guest"):
On Tue, Jun 11, 2013 at 7:21 PM, Ian Jackson <ian.jackson@xxxxxxxxxxxxx> wrote:
These functions take guest pfns and look them up in the p2m.  They did
no range checking.

However, some callers, notably xc_dom_boot.c:setup_hypercall_page want
to pass untrusted guest-supplied value(s).  It is most convenient to
detect this here and return INVALID_MFN.

This is part of the fix to a security issue, XSA-55.

Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Tim Deegan <tim@xxxxxxx>
I've taken a look at where things get returned here, and it seems like
they should all be OK with INVALID_MFN.
Good.  Does that mean that we should promote the check to be done in
the shadow_enabled case too ?

Oh sorry, missed that question.

I think it's safe, but you should get an ack from Tim to be sure.


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