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 X-Spam-Level: X-Spam-Status: No, score=-18.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 45D53C4361A for ; Fri, 4 Dec 2020 14:13:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1033F22B2D for ; Fri, 4 Dec 2020 14:13:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729029AbgLDON2 (ORCPT ); Fri, 4 Dec 2020 09:13:28 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:43505 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726763AbgLDON2 (ORCPT ); Fri, 4 Dec 2020 09:13:28 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1607091121; h=from:from: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=RL2bFLco4OUYyECE8HrwusYryV87A7DYKEYnA7i6ltI=; b=JLl/FX8Kj6JviAaV+Suxf2wxkKYYgMmsXD7hCphJn0F4/9Q6eJiz/jz0nvnXXnxfhBZEzP wUufF80Odh4F7ZUM0bNi3qlw/5RrxpJ+1/6JgsfKgMuwiCA1qEwZv/9bBsK4KONtoJr4BI VGPKgTaQ/bgmFAq6ACIzlVmktHcS5eE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-541-F5bqZjWtNOen7C0M1RJZVA-1; Fri, 04 Dec 2020 09:11:58 -0500 X-MC-Unique: F5bqZjWtNOen7C0M1RJZVA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 360A4107ACE6; Fri, 4 Dec 2020 14:11:57 +0000 (UTC) Received: from [10.36.114.254] (ovpn-114-254.ams2.redhat.com [10.36.114.254]) by smtp.corp.redhat.com (Postfix) with ESMTP id 47A7C1964B; Fri, 4 Dec 2020 14:11:55 +0000 (UTC) Subject: Re: [PATCH v2] fix mmap return value when vma is merged after call_mmap() To: Liu Zixian , akpm@linux-foundation.org, linmiaohe@huawei.com, louhongxiang@huawei.com, linux-mm@kvack.org Cc: hushiyuan@huawei.com, stable@vger.kernel.org References: <20201203085350.22624-1-liuzixian4@huawei.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Fri, 4 Dec 2020 15:11:54 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <20201203085350.22624-1-liuzixian4@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On 03.12.20 09:53, Liu Zixian wrote: > On success, mmap should return the begin address of newly mapped area, > but patch "mm: mmap: merge vma after call_mmap() if possible" > set vm_start of newly merged vma to return value addr. > Users of mmap will get wrong address if vma is merged after call_mmap(). > We fix this by moving the assignment to addr before merging vma. > > Fixes: d70cec898324 ("mm: mmap: merge vma after call_mmap() if possible") > Signed-off-by: Liu Zixian > --- > v2: > We want to do "addr = vma->vm_start;" unconditionally, > so move assignment to addr before if(unlikely) block. > --- > mm/mmap.c | 26 ++++++++++++-------------- > 1 file changed, 12 insertions(+), 14 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index d91ecb00d38c..5c8b4485860d 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -1808,6 +1808,17 @@ unsigned long mmap_region(struct file *file, unsigned long addr, > if (error) > goto unmap_and_free_vma; > > + /* Can addr have changed?? > + * > + * Answer: Yes, several device drivers can do it in their > + * f_op->mmap method. -DaveM > + * Bug: If addr is changed, prev, rb_link, rb_parent should > + * be updated for vma_link() > + */ Why do we tolerate device drivers doing such stuff at all? WARN_ON_ONCE() is just as good as BUG_ON() in many environments. If we support it, then no warning. If we don't support it, then why tolerate it? Anyhow, unrelated to your patch Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb