+ mm-list_lru-fix-uaf-for-memory-cgroup.patch added to mm-hotfixes-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

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

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------------------------------------------------------
From: Muchun Song <songmuchun@bytedance.com>
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@bytedance.com
Fixes: 0a97c01cd20bb ("list_lru: allow explicit memcg and NUMA node selection)
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 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@bytedance.com are

mm-list_lru-fix-uaf-for-memory-cgroup.patch
mm-kmem-remove-mem_cgroup_from_obj.patch