Re: [PATCH] x86/sgx: Set active memcg prior to shmem allocation

[Kristen Carlson Accardi]

On Wed, 2022-05-18 at 22:43 -0700, Shakeel Butt wrote:
> (Fixing the CC list and sending again)
> 
> On Tue, May 17, 2022 at 09:47:13AM -0700, Kristen Carlson Accardi
> wrote:
> [...]
> > +int sgx_encl_alloc_backing(struct sgx_encl *encl, unsigned long
> > page_index,
> > +                        struct sgx_backing *backing)
> > +{
> > +     struct mem_cgroup *old_memcg;
> > +     int ret;
> > +
> > +     old_memcg = sgx_encl_set_active_memcg(encl);
> 
> This function is leaking memcg reference. Please change
> sgx_encl_set_active_memcg() to sgx_encl_get_mem_cgroup() or something
> which will return the memcg with the refcount elevated. Then use
> set_active_memcg(returned_memcg) here.
> 
> > +
> > +     ret = sgx_encl_get_backing(encl, page_index, backing);
> > +
> > +     set_active_memcg(old_memcg);
> 
> mem_cgroup_put(returned_memcg) here.
> 
> > +
> > +     return ret;
> > +}

Thank you for your review. I will incorporate this fix into my next
version.