From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id E5D316B0033 for ; Tue, 31 Oct 2017 07:28:47 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id n14so14559176pfh.15 for ; Tue, 31 Oct 2017 04:28:47 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id 15si1414159pld.802.2017.10.31.04.28.46 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 31 Oct 2017 04:28:46 -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> <65c0e6cb-28b4-f202-1d7f-278b5dfc3440@huawei.com> From: Vlastimil Babka Message-ID: <1e0f1e50-4900-78d2-6586-bd68f5849337@suse.cz> Date: Tue, 31 Oct 2017 12:28:41 +0100 MIME-Version: 1.0 In-Reply-To: <65c0e6cb-28b4-f202-1d7f-278b5dfc3440@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Yisheng Xie , 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 10/31/2017 12:01 PM, Yisheng Xie wrote: > > > 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. Ugh, right. I missed that. This code is not simple... > 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 from this list: send the line "unsubscribe linux-api" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- 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