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 D9285C433EF for ; Fri, 27 May 2022 09:26:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350485AbiE0J0f (ORCPT ); Fri, 27 May 2022 05:26:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46850 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350488AbiE0J0T (ORCPT ); Fri, 27 May 2022 05:26:19 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F36A8B7D for ; Fri, 27 May 2022 02:26:16 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4L8fXm4YHvzcfdn; Fri, 27 May 2022 17:25:12 +0800 (CST) Received: from huawei.com (10.175.124.27) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 27 May 2022 17:26:14 +0800 From: Miaohe Lin To: CC: , , Subject: [PATCH 1/3] mm/swapfile: make security_vm_enough_memory_mm() work as expected Date: Fri, 27 May 2022 17:26:24 +0800 Message-ID: <20220527092626.31883-2-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20220527092626.31883-1-linmiaohe@huawei.com> References: <20220527092626.31883-1-linmiaohe@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.124.27] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org security_vm_enough_memory_mm() checks whether a process has enough memory to allocate a new virtual mapping. And total_swap_pages is considered as available memory while swapoff tries to make sure there's enough memory that can hold the swapped out memory. But total_swap_pages contains the swap space that is being swapoff. So security_vm_enough_memory_mm() will success even if there's no memory to hold the swapped out memory because total_swap_pages always greater than or equal to p->pages. In order to fix it, p->pages should be retracted from total_swap_pages first and then check whether there's enough memory for inuse swap pages. Signed-off-by: Miaohe Lin --- mm/swapfile.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index a2e66d855b19..960d14a4b19e 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2396,6 +2396,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) struct filename *pathname; int err, found = 0; unsigned int old_block_size; + unsigned int inuse_pages; if (!capable(CAP_SYS_ADMIN)) return -EPERM; @@ -2426,9 +2427,13 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) spin_unlock(&swap_lock); goto out_dput; } - if (!security_vm_enough_memory_mm(current->mm, p->pages)) - vm_unacct_memory(p->pages); + + total_swap_pages -= p->pages; + inuse_pages = READ_ONCE(p->inuse_pages); + if (!security_vm_enough_memory_mm(current->mm, inuse_pages)) + vm_unacct_memory(inuse_pages); else { + total_swap_pages += p->pages; err = -ENOMEM; spin_unlock(&swap_lock); goto out_dput; @@ -2451,7 +2456,6 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) } plist_del(&p->list, &swap_active_head); atomic_long_sub(p->pages, &nr_swap_pages); - total_swap_pages -= p->pages; p->flags &= ~SWP_WRITEOK; spin_unlock(&p->lock); spin_unlock(&swap_lock); -- 2.23.0