From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C6C4DC3A59C for ; Fri, 16 Aug 2019 11:06:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 92612205F4 for ; Fri, 16 Aug 2019 11:06:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727018AbfHPLGf (ORCPT ); Fri, 16 Aug 2019 07:06:35 -0400 Received: from mailgw01.mediatek.com ([210.61.82.183]:61533 "EHLO mailgw01.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726981AbfHPLGe (ORCPT ); Fri, 16 Aug 2019 07:06:34 -0400 X-UUID: cd793b558f0942f691fd8eb225d0e317-20190816 X-UUID: cd793b558f0942f691fd8eb225d0e317-20190816 Received: from mtkmrs01.mediatek.inc [(172.21.131.159)] by mailgw01.mediatek.com (envelope-from ) (Cellopoint E-mail Firewall v4.1.10 Build 0707 with TLS) with ESMTP id 52482549; Fri, 16 Aug 2019 19:06:25 +0800 Received: from mtkcas07.mediatek.inc (172.21.101.84) by mtkmbs01n2.mediatek.inc (172.21.101.79) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Fri, 16 Aug 2019 19:06:29 +0800 Received: from [172.21.77.33] (172.21.77.33) by mtkcas07.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1395.4 via Frontend Transport; Fri, 16 Aug 2019 19:06:29 +0800 Message-ID: <1565953586.26404.3.camel@mtkswgap22> Subject: Re: FAILED: patch "[PATCH] mm/memcontrol.c: fix use after free in mem_cgroup_iter()" failed to apply to 4.9-stable tree From: Miles Chen To: CC: , , , , , , Date: Fri, 16 Aug 2019 19:06:26 +0800 In-Reply-To: <156594986424362@kroah.com> References: <156594986424362@kroah.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit MIME-Version: 1.0 X-TM-SNTS-SMTP: AA29D158DC8AE9E3A25CD8DA13CF6DF96282DB20484D8A7870887E8394AC4B942000:8 X-MTK: N Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Fri, 2019-08-16 at 12:04 +0200, gregkh@linuxfoundation.org wrote: > The patch below does not apply to the 4.9-stable tree. > If someone wants it applied there, or to any other stable or longterm > tree, then please email the backport, including the original git commit > id to . > > thanks, > > greg k-h > Hi Greg, Below this the backport for 4.9 cheers, Miles >From e4d7e8ef4d279216930bd7f651e97db64c928b23 Mon Sep 17 00:00:00 2001 From: Miles Chen Date: Fri, 16 Aug 2019 18:31:58 +0800 Subject: [PATCH] BACKPORT: mm/memcontrol.c: fix use after free in mem_cgroup_iter() original commit id: 54a83d6bcbf8f4700013766b974bf9190d40b689 (this is This patch is sent to report an use after free in mem_cgroup_iter() after merging commit be2657752e9e ("mm: memcg: fix use after free in mem_cgroup_iter()"). I work with android kernel tree (4.9 & 4.14), and commit be2657752e9e ("mm: memcg: fix use after free in mem_cgroup_iter()") has been merged to the trees. However, I can still observe use after free issues addressed in the commit be2657752e9e. (on low-end devices, a few times this month) backtrace: css_tryget <- crash here mem_cgroup_iter shrink_node shrink_zones do_try_to_free_pages try_to_free_pages __perform_reclaim __alloc_pages_direct_reclaim __alloc_pages_slowpath __alloc_pages_nodemask To debug, I poisoned mem_cgroup before freeing it: static void __mem_cgroup_free(struct mem_cgroup *memcg) for_each_node(node) free_mem_cgroup_per_node_info(memcg, node); free_percpu(memcg->stat); + /* poison memcg before freeing it */ + memset(memcg, 0x78, sizeof(struct mem_cgroup)); kfree(memcg); } The coredump shows the position=0xdbbc2a00 is freed. (gdb) p/x ((struct mem_cgroup_per_node *)0xe5009e00)->iter[8] $13 = {position = 0xdbbc2a00, generation = 0x2efd} 0xdbbc2a00: 0xdbbc2e00 0x00000000 0xdbbc2800 0x00000100 0xdbbc2a10: 0x00000200 0x78787878 0x00026218 0x00000000 0xdbbc2a20: 0xdcad6000 0x00000001 0x78787800 0x00000000 0xdbbc2a30: 0x78780000 0x00000000 0x0068fb84 0x78787878 0xdbbc2a40: 0x78787878 0x78787878 0x78787878 0xe3fa5cc0 0xdbbc2a50: 0x78787878 0x78787878 0x00000000 0x00000000 0xdbbc2a60: 0x00000000 0x00000000 0x00000000 0x00000000 0xdbbc2a70: 0x00000000 0x00000000 0x00000000 0x00000000 0xdbbc2a80: 0x00000000 0x00000000 0x00000000 0x00000000 0xdbbc2a90: 0x00000001 0x00000000 0x00000000 0x00100000 0xdbbc2aa0: 0x00000001 0xdbbc2ac8 0x00000000 0x00000000 0xdbbc2ab0: 0x00000000 0x00000000 0x00000000 0x00000000 0xdbbc2ac0: 0x00000000 0x00000000 0xe5b02618 0x00001000 0xdbbc2ad0: 0x00000000 0x78787878 0x78787878 0x78787878 0xdbbc2ae0: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2af0: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b00: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b10: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b20: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b30: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b40: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b50: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b60: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b70: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b80: 0x78787878 0x78787878 0x00000000 0x78787878 0xdbbc2b90: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2ba0: 0x78787878 0x78787878 0x78787878 0x78787878 In the reclaim path, try_to_free_pages() does not setup sc.target_mem_cgroup and sc is passed to do_try_to_free_pages(), ..., shrink_node(). In mem_cgroup_iter(), root is set to root_mem_cgroup because sc->target_mem_cgroup is NULL. It is possible to assign a memcg to root_mem_cgroup.nodeinfo.iter in mem_cgroup_iter(). try_to_free_pages struct scan_control sc = {...}, target_mem_cgroup is 0x0; do_try_to_free_pages shrink_zones shrink_node mem_cgroup *root = sc->target_mem_cgroup; memcg = mem_cgroup_iter(root, NULL, &reclaim); mem_cgroup_iter() if (!root) root = root_mem_cgroup; ... css = css_next_descendant_pre(css, &root->css); memcg = mem_cgroup_from_css(css); cmpxchg(&iter->position, pos, memcg); My device uses memcg non-hierarchical mode. When we release a memcg: invalidate_reclaim_iterators() reaches only dead_memcg and its parents. If non-hierarchical mode is used, invalidate_reclaim_iterators() never reaches root_mem_cgroup. static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg) { struct mem_cgroup *memcg = dead_memcg; for (; memcg; memcg = parent_mem_cgroup(memcg) ... } So the use after free scenario looks like: CPU1 CPU2 try_to_free_pages do_try_to_free_pages shrink_zones shrink_node mem_cgroup_iter() if (!root) root = root_mem_cgroup; ... css = css_next_descendant_pre(css, &root->css); memcg = mem_cgroup_from_css(css); cmpxchg(&iter->position, pos, memcg); invalidate_reclaim_iterators(memcg); ... __mem_cgroup_free() kfree(memcg); try_to_free_pages do_try_to_free_pages shrink_zones shrink_node mem_cgroup_iter() if (!root) root = root_mem_cgroup; ... mz = mem_cgroup_nodeinfo(root, reclaim->pgdat->node_id); iter = &mz->iter[reclaim->priority]; pos = READ_ONCE(iter->position); css_tryget(&pos->css) <- use after free To avoid this, we should also invalidate root_mem_cgroup.nodeinfo.iter in invalidate_reclaim_iterators(). [cai@lca.pw: fix -Wparentheses compilation warning] Link: http://lkml.kernel.org/r/1564580753-17531-1-git-send-email-cai@lca.pw Link: http://lkml.kernel.org/r/20190730015729.4406-1-miles.chen@mediatek.com Fixes: 5ac8fb31ad2e ("mm: memcontrol: convert reclaim iterator to simple css refcounting") Signed-off-by: Miles Chen Signed-off-by: Qian Cai Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Vladimir Davydov Cc: Signed-off-by: Andrew Morton Signed-off-by: Stephen Rothwell --- mm/memcontrol.c | 39 +++++++++++++++++++++++++++++---------- 1 file changed, 29 insertions(+), 10 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 661f046ad318..6bbe556b2155 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -871,26 +871,45 @@ void mem_cgroup_iter_break(struct mem_cgroup *root, css_put(&prev->css); } -static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg) +static void __invalidate_reclaim_iterators(struct mem_cgroup *from, + struct mem_cgroup *dead_memcg) { - struct mem_cgroup *memcg = dead_memcg; struct mem_cgroup_reclaim_iter *iter; struct mem_cgroup_per_node *mz; int nid; int i; - while ((memcg = parent_mem_cgroup(memcg))) { - for_each_node(nid) { - mz = mem_cgroup_nodeinfo(memcg, nid); - for (i = 0; i <= DEF_PRIORITY; i++) { - iter = &mz->iter[i]; - cmpxchg(&iter->position, - dead_memcg, NULL); - } + for_each_node(nid) { + mz = mem_cgroup_nodeinfo(from, nid); + for (i = 0; i <= DEF_PRIORITY; i++) { + iter = &mz->iter[i]; + cmpxchg(&iter->position, + dead_memcg, NULL); } } } +static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg) +{ + struct mem_cgroup *memcg = dead_memcg; + struct mem_cgroup *last; + + do { + __invalidate_reclaim_iterators(memcg, dead_memcg); + last = memcg; + } while ((memcg = parent_mem_cgroup(memcg))); + + /* + * When cgruop1 non-hierarchy mode is used, + * parent_mem_cgroup() does not walk all the way up to the + * cgroup root (root_mem_cgroup). So we have to handle + * dead_memcg from cgroup root separately. + */ + if (last != root_mem_cgroup) + __invalidate_reclaim_iterators(root_mem_cgroup, + dead_memcg); +} + /* * Iteration constructs for visiting all cgroups (under a tree). If * loops are exited prematurely (break), mem_cgroup_iter_break() must -- 2.18.0