Re: [Xen-devel] [PATCH] viridian: make viridian_time_domain_freeze() safe to call...

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Aug 21, 2019 at 09:22:58AM +0100, Paul Durrant wrote:
> ...on a partially destroyed domain.
> 
> viridian_time_domain_freeze() and viridian_time_vcpu_freeze() rely
> (respectively) on the dynamically allocated per-domain and per-vcpu viridian
> areas [1], which are freed during domain_relinquish_resources().
> Because arch_domain_pause() can call viridian_domain_time_freeze() this
> can lead to host crashes if e.g. a XEN_DOMCTL_pausedomain is issued after
> domain_relinquish_resources() has run.
> 
> To prevent such crashes, this patch adds a check of is_dying into
> viridian_time_domain_freeze(), and viridian_time_domain_thaw() which is
> similarly vulnerable to indirection into freed memory.
> 
> NOTE: The patch also makes viridian_time_vcpu_freeze/thaw() static, since
>       they have no callers outside of the same source module.
> 
> [1] See commit e7a9b5e72f26 "viridian: separately allocate domain and vcpu
>     structures".
> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Note you could also drop the viridian_ prefix to the now static
functions.

Thanks, Roger.

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