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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6B5DBECAAD5 for ; Mon, 12 Sep 2022 07:29:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C46878D0002; Mon, 12 Sep 2022 03:29:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BCEEE8D0001; Mon, 12 Sep 2022 03:29:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A6F5F8D0002; Mon, 12 Sep 2022 03:29:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 8FFC18D0001 for ; Mon, 12 Sep 2022 03:29:49 -0400 (EDT) Received: from smtpin24.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 69E9AA0824 for ; Mon, 12 Sep 2022 07:29:49 +0000 (UTC) X-FDA: 79902608898.24.C03C98F Received: from out30-43.freemail.mail.aliyun.com (out30-43.freemail.mail.aliyun.com [115.124.30.43]) by imf14.hostedemail.com (Postfix) with ESMTP id D5141100099 for ; Mon, 12 Sep 2022 07:29:47 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046059;MF=luoben@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0VPQS590_1662967771; Received: from B-530WMD6R-2112.local(mailfrom:luoben@linux.alibaba.com fp:SMTPD_---0VPQS590_1662967771) by smtp.aliyun-inc.com; Mon, 12 Sep 2022 15:29:44 +0800 Subject: Re: [PATCH] mm/slub: return 0 when object pointer is NULL To: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, vbabka@suse.cz, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1662962379-16174-1-git-send-email-luoben@linux.alibaba.com> From: Ben Luo Message-ID: <133458f0-23c9-9421-abb8-a50d5551b524@linux.alibaba.com> Date: Mon, 12 Sep 2022 15:29:30 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662967789; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=sbSz0iGcHs37MTgMxX/PYxah8Mrr55oXDHTF/bEwz/c=; b=Hb0bqwh61qXdXV60jeZsaWHpOfy/Z+7W749/JilLIs3ClIz4zne85XSW20F7j2qc+vVU6m VzQGV6YFp/6M6Mr9fn/jHeLl4bpr+VWhkwO5JC0SWfamxUYhYJ8AEKbjHg/Sa8GnBbCJnZ 73VfaBHJd2QX4AGNVhAiDp/qdCZ1utk= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=none; spf=pass (imf14.hostedemail.com: domain of luoben@linux.alibaba.com designates 115.124.30.43 as permitted sender) smtp.mailfrom=luoben@linux.alibaba.com; dmarc=pass (policy=none) header.from=alibaba.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662967789; a=rsa-sha256; cv=none; b=c8pPMWMdisTmbDBjwAA39MJHquZS7jfNCaQzSOaQua0HKDBI71IHpa/R5uDK/gbvq2odVP RYoCYP0UFWP8AARUA5uRcP1w//ioUaqE80PevUCAYEJKIHnyPnoY2rAypMnZQAHr8dqdWn H0J52HDi84hppWqS96sdH3Jwb2hOIqM= X-Stat-Signature: fngkc8weqycrp7xbckc681cau749iawu X-Rspamd-Queue-Id: D5141100099 X-Rspam-User: Authentication-Results: imf14.hostedemail.com; dkim=none; spf=pass (imf14.hostedemail.com: domain of luoben@linux.alibaba.com designates 115.124.30.43 as permitted sender) smtp.mailfrom=luoben@linux.alibaba.com; dmarc=pass (policy=none) header.from=alibaba.com X-Rspamd-Server: rspam03 X-HE-Tag: 1662967787-339720 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hello Hyeonggon, Thanks for replying :) 在 2022/9/12 15:18, Hyeonggon Yoo 写道: > On Mon, Sep 12, 2022 at 01:59:39PM +0800, Ben Luo wrote: >> NULL is definitly not a valid address >> >> Signed-off-by: Ben Luo >> --- >> mm/slub.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/slub.c b/mm/slub.c >> index 862dbd9..50fad18 100644 >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -674,7 +674,7 @@ static inline int check_valid_pointer(struct kmem_cache *s, >> void *base; >> >> if (!object) >> - return 1; >> + return 0; >> >> base = slab_address(slab); >> object = kasan_reset_tag(object); >> -- >> 1.8.3.1 >> > Hello Ben. > > The return value is used to check if the @object has valid pointer > in @slab. (used for debugging) the return value is 0 if valid, 1 if invalid. > > It does not return a pointer. So changing it to 0 because 1 is invalid > address does not make sense. I know the meaning of this return value, but I think this function was expected by returning 0 if invalid ,1 if valid Check this original code:         if (object < base || object >= base + slab->objects * s->size ||                 (object - base) % s->size) {                 return 0;         } Object not in range of [base, base+length) is an invalid slab address, and it will return 0 -- Thanks, Ben >