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 ADAABC4332F for ; Thu, 29 Dec 2022 07:48:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233060AbiL2Hsf (ORCPT ); Thu, 29 Dec 2022 02:48:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58490 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233065AbiL2HsR (ORCPT ); Thu, 29 Dec 2022 02:48:17 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3768FB844 for ; Wed, 28 Dec 2022 23:48:14 -0800 (PST) Received: from dggpemm500014.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4NjL3v5GhHzkX1g; Thu, 29 Dec 2022 15:43:39 +0800 (CST) Received: from [10.174.178.120] (10.174.178.120) 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 15.1.2375.34; Thu, 29 Dec 2022 15:48:12 +0800 Message-ID: Date: Thu, 29 Dec 2022 15:48:12 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 From: mawupeng Subject: Re: [PATCH 1/4] mm/mlock: return EINVAL for illegal user memory range in mlock To: CC: , , , , , References: <20221205034108.3365182-1-mawupeng1@huawei.com> <20221205034108.3365182-2-mawupeng1@huawei.com> <20221228141701.c64add46c4b09aa17f605baf@linux-foundation.org> Content-Language: en-US In-Reply-To: <20221228141701.c64add46c4b09aa17f605baf@linux-foundation.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.120] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) 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 On 2022/12/29 6:17, Andrew Morton wrote: > On Mon, 5 Dec 2022 11:41:05 +0800 Wupeng Ma wrote: > >> While testing mlock, we have a problem if the len of mlock is ULONG_MAX. >> The return value of mlock is zero. But nothing will be locked since the >> len in do_mlock overflows to zero due to the following code in mlock: >> >> len = PAGE_ALIGN(len + (offset_in_page(start))); >> >> The same problem happens in munlock. >> >> Since TASK_SIZE is the maximum user space address. The start or len of >> mlock shouldn't be bigger than this. Function access_ok can be used to >> check this issue, so return -EINVAL if bigger. > > What happens if userspace uses a value somewhat smaller than ULONG_MAX? > > mlock(addr, ULONG_MAX - 1000000); > > ? > > Because if the above works successfully and if it no longer works > successfully with this patchset then that could be a > backward-compatibility problem. For mlock: mlock(addr, ULONG_MAX - 1000000) will ret -1 and the errno is EINVAL(22) due to the following call trace. do_mlock apply_vma_lock_flags end = start + len; if (end < start) return -EINVAL; Just like you said, we need to keep backward-compatibility. Maybe we can only catch and fix the overflowing scenarios since they are absolutely wrong. here is the diff: diff --git a/mm/mlock.c b/mm/mlock.c index 7032f6dd0ce1..fd5e857ab245 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -569,6 +569,7 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla unsigned long locked; unsigned long lock_limit; int error = -ENOMEM; + size_t old_len = len; start = untagged_addr(start); @@ -578,6 +579,9 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla len = PAGE_ALIGN(len + (offset_in_page(start))); start &= PAGE_MASK; + if (old_len != 0 && len == 0) + return -EINVAL; + lock_limit = rlimit(RLIMIT_MEMLOCK); lock_limit >>= PAGE_SHIFT; locked = len >> PAGE_SHIFT; >