CVE-2024-43888

In the Linux kernel, the following vulnerability has been resolved:

mm: list_lru: fix UAF for memory cgroup

The mem_cgroup_from_slab_obj() is supposed to be called under rcu lock or
cgroup_mutex or others which could prevent returned memcg from being
freed. Fix it by adding missing rcu read lock.

Found by code inspection.

[songmuchun@bytedance.com: only grab rcu lock when necessary, per Vlastimil]