The patch titled Subject: mm: list_lru: fix UAF for memory cgroup has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-list_lru-fix-uaf-for-memory-cgroup.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-list_lru-fix-uaf-for-memory-cgroup.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Muchun Song <songmuchun@xxxxxxxxxxxxx> Subject: mm: list_lru: fix UAF for memory cgroup Date: Thu, 18 Jul 2024 16:36:07 +0800 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. Link: https://lkml.kernel.org/r/20240718083607.42068-1-songmuchun@xxxxxxxxxxxxx Fixes: 0a97c01cd20bb ("list_lru: allow explicit memcg and NUMA node selection) Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> Acked-by: Shakeel Butt <shakeel.butt@xxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Nhat Pham <nphamcs@xxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/list_lru.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) --- a/mm/list_lru.c~mm-list_lru-fix-uaf-for-memory-cgroup +++ a/mm/list_lru.c @@ -85,6 +85,7 @@ list_lru_from_memcg_idx(struct list_lru } #endif /* CONFIG_MEMCG */ +/* 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; + + 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 list_lru_del(lru, item, nid, memcg); + return ret; } EXPORT_SYMBOL_GPL(list_lru_del_obj); _ Patches currently in -mm which might be from songmuchun@xxxxxxxxxxxxx are mm-list_lru-fix-uaf-for-memory-cgroup.patch mm-kmem-remove-mem_cgroup_from_obj.patch