From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f69.google.com (mail-oi0-f69.google.com [209.85.218.69]) by kanga.kvack.org (Postfix) with ESMTP id 906716B0038 for ; Tue, 31 Oct 2017 07:03:01 -0400 (EDT) Received: by mail-oi0-f69.google.com with SMTP id e123so18660407oig.14 for ; Tue, 31 Oct 2017 04:03:01 -0700 (PDT) Received: from szxga04-in.huawei.com (szxga04-in.huawei.com. [45.249.212.190]) by mx.google.com with ESMTPS id u191si768408oia.102.2017.10.31.04.02.59 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 31 Oct 2017 04:03:00 -0700 (PDT) Subject: Re: [PATCH RFC v2 3/4] mm/mempolicy: fix the check of nodemask from user References: <1509099265-30868-1-git-send-email-xieyisheng1@huawei.com> <1509099265-30868-4-git-send-email-xieyisheng1@huawei.com> <56c4cdbf-c228-6203-285c-15f19a841538@suse.cz> From: Yisheng Xie Message-ID: <65c0e6cb-28b4-f202-1d7f-278b5dfc3440@huawei.com> Date: Tue, 31 Oct 2017 19:01:06 +0800 MIME-Version: 1.0 In-Reply-To: <56c4cdbf-c228-6203-285c-15f19a841538@suse.cz> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka , akpm@linux-foundation.org, mhocko@suse.com, mingo@kernel.org, rientjes@google.com, n-horiguchi@ah.jp.nec.com, salls@cs.ucsb.edu Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, tanxiaojun@huawei.com, linux-api@vger.kernel.org On 2017/10/31 17:30, Vlastimil Babka wrote: > On 10/27/2017 12:14 PM, Yisheng Xie wrote: >> + /* >> + * When the user specified more nodes than supported just check >> + * if the non supported part is all zero. >> + * >> + * If maxnode have more longs than MAX_NUMNODES, check >> + * the bits in that area first. And then go through to >> + * check the rest bits which equal or bigger than MAX_NUMNODES. >> + * Otherwise, just check bits [MAX_NUMNODES, maxnode). >> + */ >> if (nlongs > BITS_TO_LONGS(MAX_NUMNODES)) { >> for (k = BITS_TO_LONGS(MAX_NUMNODES); k < nlongs; k++) { >> - unsigned long t; >> if (get_user(t, nmask + k)) >> return -EFAULT; >> if (k == nlongs - 1) { >> @@ -1294,6 +1301,16 @@ static int get_nodes(nodemask_t *nodes, const unsigned long __user *nmask, >> endmask = ~0UL; >> } >> >> + if (maxnode > MAX_NUMNODES && MAX_NUMNODES % BITS_PER_LONG != 0) { >> + unsigned long valid_mask = endmask; >> + >> + valid_mask &= ~((1UL << (MAX_NUMNODES % BITS_PER_LONG)) - 1); > > I'm not sure if the combination with endmask works in this case: > > 0 BITS_PER_LONG 2xBITS_PER_LONG > |____________|____________| > | | > MAX_NUMNODES maxnode > > endmask will contain bits between 0 and maxnode In the case, BITS_TO_LONGS(maxnode) > BITS_TO_LONGS(MAX_NUMNODES), right? And after checking BITS_PER_LONG to 2xBITS_PER_LONGi 1/4 ?endmask will set to "~0UL". e.g. endmask will be 0xffff ffff ffff ffff if unsigned long is 64bit. Then the valid_mask will just contain bits MAX_NUMNODES to BITS_PER_LONG. Thanks Yisheng Xie > but here we want to check bits between MAX_NUMNODES and BITS_PER_LONG > and endmask should not be mixed up with that? > > > Vlastimil > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org