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DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns,suse.cz:dkim] X-Spam-Flag: NO X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Score: -4.50 X-Spam-Level: X-Rspamd-Queue-Id: E1564218C8 On 7/18/24 10:36 AM, Muchun Song wrote: > 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. Was the UAF ever observed, or is this due to code review? Should there be some lockdep_assert somwhere? > Fixes: 0a97c01cd20bb ("list_lru: allow explicit memcg and NUMA node selection) > Signed-off-by: Muchun Song > --- > mm/list_lru.c | 24 ++++++++++++++++++------ > 1 file changed, 18 insertions(+), 6 deletions(-) > > diff --git a/mm/list_lru.c b/mm/list_lru.c > index 3fd64736bc458..225da0778a3be 100644 > --- a/mm/list_lru.c > +++ b/mm/list_lru.c > @@ -85,6 +85,7 @@ list_lru_from_memcg_idx(struct list_lru *lru, int nid, int idx) > } > #endif /* CONFIG_MEMCG_KMEM */ > > +/* The caller must ensure the memcg lifetime. */ > bool list_lru_add(struct list_lru *lru, struct list_head *item, int nid, > struct mem_cgroup *memcg) > { > @@ -109,14 +110,20 @@ EXPORT_SYMBOL_GPL(list_lru_add); > > bool list_lru_add_obj(struct list_lru *lru, struct list_head *item) > { > + bool ret; > int nid = page_to_nid(virt_to_page(item)); > - struct mem_cgroup *memcg = list_lru_memcg_aware(lru) ? > - mem_cgroup_from_slab_obj(item) : NULL; > + struct mem_cgroup *memcg; > > - return list_lru_add(lru, item, nid, memcg); > + rcu_read_lock(); > + memcg = list_lru_memcg_aware(lru) ? mem_cgroup_from_slab_obj(item) : NULL; > + ret = list_lru_add(lru, item, nid, memcg); > + rcu_read_unlock(); > + > + return ret; > } > EXPORT_SYMBOL_GPL(list_lru_add_obj); > > +/* The caller must ensure the memcg lifetime. */ > bool list_lru_del(struct list_lru *lru, struct list_head *item, int nid, > struct mem_cgroup *memcg) > { > @@ -139,11 +146,16 @@ EXPORT_SYMBOL_GPL(list_lru_del); > > bool list_lru_del_obj(struct list_lru *lru, struct list_head *item) > { > + bool ret; > int nid = page_to_nid(virt_to_page(item)); > - struct mem_cgroup *memcg = list_lru_memcg_aware(lru) ? > - mem_cgroup_from_slab_obj(item) : NULL; > + struct mem_cgroup *memcg; > > - return list_lru_del(lru, item, nid, memcg); > + rcu_read_lock(); > + memcg = list_lru_memcg_aware(lru) ? mem_cgroup_from_slab_obj(item) : NULL; > + ret = list_lru_del(lru, item, nid, memcg); > + rcu_read_unlock(); > + > + return ret; > } > EXPORT_SYMBOL_GPL(list_lru_del_obj); >