Re: [Xen-devel] [PATCH v2] tools/libxc: Prevent erroneous success from xc_domain_restore

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-02-05 at 14:55 +0000, George Dunlap wrote:
> On 02/04/2014 06:01 PM, Andrew Cooper wrote:
> > The variable 'rc' is set to 1 at the top of xc_domain_restore, and for the
> > most part is left alone until success, at which point it is set to 0.
> >
> > There is a separate 'frc' which for the most part is used to check function
> > calls, keeping errors separate from 'rc'.
> >
> > For a toolstack which sets callbacks->toolstack_restore(), and the function
> > returns 0, any subsequent error will end up with code flow going to "out;",
> > resulting in the migration being declared a success.
> >
> > For consistency, update the callsites of xc_dom_gnttab{,_hvm}_seed() to use
> > 'frc', even though their use of 'rc' is currently safe.
> >
> > Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
> > CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
> > CC: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> >
> > ---
> >
> > Changes in v2:
> >   * Dont drop rc = -1 from toolstack_restore().
> >
> > Regarding 4.4: If the two "for consistency" changes to
> > xc_dom_gnttab{,_hvm}_seed() are considered too risky, they can be dropped
> > without affecting the bugfix nature of the patch, but I would argue that
> > leaving some examples of "rc = function_call()" leaves a bad precident which
> > is likely to lead to similar bugs in the future.
> 
> Yes, these are all pretty clear bug fixes.
> 
> Release-acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>

Applied.


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