mm-damon-core-get-memcg-reference-before-access.patch removed from -mm tree

The quilt patch titled
Subject: mm/damon/core: get memcg reference before access
has been removed from the -mm tree. Its filename was
mm-damon-core-get-memcg-reference-before-access.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Shakeel Butt <[email protected]>
Subject: mm/damon/core: get memcg reference before access
Date: Wed, 24 Dec 2025 16:29:04 -0800

The commit b74a120bcf507 ("mm/damon/core: implement DAMOS_QUOTA_NODE_MEMCG_USED_BP") added accesses to memcg structure without getting reference to it. This is unsafe. Let's get the reference before accessing the memcg.

---

 mm/damon/core.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

@@ -2051,13 +2051,15 @@ static unsigned long damos_get_node_memc
 
 	rcu_read_lock();
 	memcg = mem_cgroup_from_id(goal->memcg_id);
-	rcu_read_unlock();
-	if (!memcg) {
+	if (!memcg || !mem_cgroup_tryget(memcg)) {
+		rcu_read_unlock();
 		if (goal->metric == DAMOS_QUOTA_NODE_MEMCG_USED_BP)
 			return 0;
 		else	/* DAMOS_QUOTA_NODE_MEMCG_FREE_BP */
 			return 10000;
 	}
+	rcu_read_unlock();
+
 	mem_cgroup_flush_stats(memcg);
 	lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(goal->nid));
 	used_pages = lruvec_page_state(lruvec, NR_ACTIVE_ANON);

@@ -2065,6 +2067,8 @@ static unsigned long damos_get_node_memc
 	used_pages += lruvec_page_state(lruvec, NR_ACTIVE_FILE);
 	used_pages += lruvec_page_state(lruvec, NR_INACTIVE_FILE);
 
+	mem_cgroup_put(memcg);
+
 	si_meminfo_node(&i, goal->nid);
 	if (goal->metric == DAMOS_QUOTA_NODE_MEMCG_USED_BP)
 		numerator = used_pages;

_

Patches currently in -mm which might be from [email protected] are

memcg-introduce-private-id-api-for-in-kernel-users.patch memcg-expose-mem_cgroup_ino-and-mem_cgroup_get_from_ino-unconditionally.patch memcg-mem_cgroup_get_from_ino-returns-null-on-error.patch memcg-use-cgroup_id-instead-of-cgroup_ino-for-memcg-id.patch mm-damon-use-cgroup-id-instead-of-private-memcg-id.patch mm-vmscan-use-cgroup-id-instead-of-private-memcg-id-in-lru_gen-interface.patch memcg-remove-unused-mem_cgroup_id-and-mem_cgroup_from_id.patch memcg-rename-mem_cgroup_ino-to-mem_cgroup_id.patch memcg-rename-mem_cgroup_ino-to-mem_cgroup_id-fix.patch