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

[George Dunlap <george.dunlap@eu.citrix.com>]

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@citrix.com>
> CC: Ian Campbell <Ian.Campbell@citrix.com>
> CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
> CC: George Dunlap <george.dunlap@eu.citrix.com>
>
> ---
>
> 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@eu.citrix.com>