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[188.141.5.72]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43b64717e97sm25121657f8f.35.2026.03.22.12.36.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 22 Mar 2026 12:36:34 -0700 (PDT) From: David Carlier To: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Qi Zheng Cc: linux-mm@kvack.org, David Carlier , stable@vger.kernel.org Subject: [PATCH] mm/memcontrol: fix obj_cgroup leak in mem_cgroup_css_online() error path Date: Sun, 22 Mar 2026 19:36:31 +0000 Message-ID: <20260322193631.45457-1-devnexen@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260322080142.5834-1-devnexen@gmail.com> References: <20260322080142.5834-1-devnexen@gmail.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When obj_cgroup_alloc() fails partway through the NUMA node loop in mem_cgroup_css_online(), the free_objcg error path drops the extra reference held by pn->orig_objcg but never kills the initial percpu_ref from obj_cgroup_alloc() stored in pn->objcg. Since css_offline is never called when css_online fails, memcg_reparent_objcgs() never runs, so the percpu_ref_kill() that normally drops this initial reference never executes. The obj_cgroup and its per-cpu ref allocations are leaked. Clear pn->objcg via rcu_replace_pointer() and add the missing percpu_ref_kill() in the error path, matching the normal teardown sequence in memcg_reparent_objcgs(). Also add a NULL check for pn in __mem_cgroup_free() to prevent a NULL pointer dereference when alloc_mem_cgroup_per_node_info() fails partway through the node loop in mem_cgroup_alloc(). Fixes: 098fad3e1621 ("mm: memcontrol: convert objcg to be per-memcg per-node type") Cc: stable@vger.kernel.org Signed-off-by: David Carlier --- mm/memcontrol.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index a47fb68dd65f..00b3bb81aee4 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3936,6 +3936,8 @@ static void __mem_cgroup_free(struct mem_cgroup *memcg) for_each_node(node) { struct mem_cgroup_per_node *pn = memcg->nodeinfo[node]; + if (!pn) + continue; obj_cgroup_put(pn->orig_objcg); free_mem_cgroup_per_node_info(pn); @@ -4137,8 +4139,11 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css) free_objcg: for_each_node(nid) { struct mem_cgroup_per_node *pn = memcg->nodeinfo[nid]; + objcg = rcu_replace_pointer(pn->objcg, NULL, true); + if (objcg) + percpu_ref_kill(&objcg->refcnt); - if (pn && pn->orig_objcg) { + if (pn->orig_objcg) { obj_cgroup_put(pn->orig_objcg); /* * Reset pn->orig_objcg to NULL to prevent -- 2.53.0