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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CC181C00144 for ; Tue, 2 Aug 2022 01:33:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234882AbiHBBdY (ORCPT ); Mon, 1 Aug 2022 21:33:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55572 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231215AbiHBBdV (ORCPT ); Mon, 1 Aug 2022 21:33:21 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 78118EE0B for ; Mon, 1 Aug 2022 18:33:19 -0700 (PDT) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.57]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Lxcpj4d2SzWf48; Tue, 2 Aug 2022 09:29:17 +0800 (CST) Received: from dggpemm500014.china.huawei.com (7.185.36.153) by dggpemm500024.china.huawei.com (7.185.36.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 2 Aug 2022 09:33:16 +0800 Received: from localhost.localdomain (10.175.112.125) by dggpemm500014.china.huawei.com (7.185.36.153) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 2 Aug 2022 09:33:15 +0800 From: Wupeng Ma To: , , , CC: , , , , Subject: [PATCH stable 4.14,4.19 1/1] mm: Fix page counter mismatch in shmem_mfill_atomic_pte Date: Tue, 2 Aug 2022 09:32:51 +0800 Message-ID: <20220802013251.3022141-1-mawupeng1@huawei.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.112.125] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemm500014.china.huawei.com (7.185.36.153) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ma Wupeng shmem_mfill_atomic_pte() wrongly called mem_cgroup_cancel_charge() in "success" path, it should mem_cgroup_uncharge() to dec memory counter instead. mem_cgroup_cancel_charge() should only be used if this transaction is unsuccessful and mem_cgroup_uncharge() is used to do this if this transaction succeed. This will lead to page->memcg not null and will uncharge one more in put_page(). The page counter will underflow to maximum value and trigger oom to kill all process include sshd and leave system unaccessible. page->memcg is set in the following path: mem_cgroup_commit_charge commit_charge page->mem_cgroup = memcg; extra uncharge will be done in the following path: put_page __put_page __put_single_page mem_cgroup_uncharge if (!page->mem_cgroup) <-- should return here return uncharge_page uncharge_batch To fix this, call mem_cgroup_commit_charge() at the end of this transaction to make sure this transaction is really finished. Fixes: 4c27fe4c4c84 ("userfaultfd: shmem: add shmem_mcopy_atomic_pte for userfaultfd support") Signed-off-by: Ma Wupeng --- mm/shmem.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 0788616696dc..0b06724c189e 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2339,8 +2339,6 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, if (ret) goto out_release_uncharge; - mem_cgroup_commit_charge(page, memcg, false, false); - _dst_pte = mk_pte(page, dst_vma->vm_page_prot); if (dst_vma->vm_flags & VM_WRITE) _dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte)); @@ -2366,6 +2364,8 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, if (!pte_none(*dst_pte)) goto out_release_uncharge_unlock; + mem_cgroup_commit_charge(page, memcg, false, false); + lru_cache_add_anon(page); spin_lock_irq(&info->lock); -- 2.25.1