From nobody Sat Sep 13 22:28:06 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6B9AC38142 for ; Sun, 29 Jan 2023 02:22:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234039AbjA2CWZ (ORCPT ); Sat, 28 Jan 2023 21:22:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57010 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231126AbjA2CWX (ORCPT ); Sat, 28 Jan 2023 21:22:23 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DC0D976B0 for ; Sat, 28 Jan 2023 18:22:21 -0800 (PST) Received: from dggpemm500001.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4P4FR31FQ4zJrKm; Sun, 29 Jan 2023 10:20:47 +0800 (CST) Received: from localhost.localdomain.localdomain (10.175.113.25) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.34; Sun, 29 Jan 2023 10:22:19 +0800 From: Kefeng Wang To: Andrew Morton CC: Tejun Heo , Jens Axboe , Jan Kara , Shakeel Butt , Naoya Horiguchi , , , Kefeng Wang , Ma Wupeng Subject: [PATCH] mm: memcg: fix NULL pointer in mem_cgroup_track_foreign_dirty() Date: Sun, 29 Jan 2023 10:44:51 +0800 Message-ID: <20230129024451.121590-1-wangkefeng.wang@huawei.com> X-Mailer: git-send-email 2.35.3 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.175.113.25] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" As commit 18365225f044 ("hwpoison, memcg: forcibly uncharge LRU pages"), hwpoison will forcibly uncharg a LRU hwpoisoned page, the folio_memcg could be NULl, then, mem_cgroup_track_foreign_dirty_slowpath() could occurs a NULL pointer dereference, let's do not record the foreign writebacks for folio memcg is null in mem_cgroup_track_foreign() to fix it. Reported-by: Ma Wupeng Fixes: 97b27821b485 ("writeback, memcg: Implement foreign dirty flushing") Signed-off-by: Kefeng Wang Acked-by: Michal Hocko Reported-by!) --- include/linux/memcontrol.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index eb6e5b18e1ad..35478695cabf 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1688,10 +1688,13 @@ void mem_cgroup_track_foreign_dirty_slowpath(struct= folio *folio, static inline void mem_cgroup_track_foreign_dirty(struct folio *folio, struct bdi_writeback *wb) { + struct mem_cgroup *memcg; + if (mem_cgroup_disabled()) return; =20 - if (unlikely(&folio_memcg(folio)->css !=3D wb->memcg_css)) + memcg =3D folio_memcg(folio); + if (unlikely(memcg && &memcg->css !=3D wb->memcg_css)) mem_cgroup_track_foreign_dirty_slowpath(folio, wb); } =20 --=20 2.35.3