[libvirt] [PATCH for v4.6.0] cgroups: Don't leave stale pointers around after virCgroupFree

[Daniel P. Berrangé]

On Mon, Jul 30, 2018 at 09:48:51AM +0100, Daniel P. Berrangé wrote:
> On Mon, Jul 30, 2018 at 10:25:05AM +0200, Michal Privoznik wrote:
> > One of the attributes that original virCgroupFree() had was it
> > set passed pointer to NULL. For instance in the following code
> > the latter call would be practically a no-op:
> > 
> >   virCgroupFree(&var);
> >   virCgroupFree(&var);
> > 
> > However, this behaviour of the function was changed in
> > 0f80c71822d824 but corresponding 'var = NULL' lines were not
> > added leading to double free:
> 
> Sigh, can we please just revert that change. It is going in completely the
> oppposite of what we should be doing. We want to change more functions to
> take a ptr to a ptr, precisely because it avoids this double-free problem.

Even more crazy, this change was done so that VIR_DEFINE_AUTOPTR_FUNC()
could be used to define a free function which takes a ptr to a ptr.

Both of these changes should be reverted, as the previously existing
virCgroupFree should be used as the attribute((cleanup)) function directly
with no wrapper created.

Regards,
Daniel
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