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

[Shakeel Butt <shakeelb@google.com>]

(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;
> +}