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 D13A6C6FA82 for ; Mon, 19 Sep 2022 20:57:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1114E6B0071; Mon, 19 Sep 2022 16:57:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 099826B0072; Mon, 19 Sep 2022 16:57:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E7C38940007; Mon, 19 Sep 2022 16:57:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id D5C7B6B0071 for ; Mon, 19 Sep 2022 16:57:24 -0400 (EDT) Received: from smtpin12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 985CC80C9E for ; Mon, 19 Sep 2022 20:57:24 +0000 (UTC) X-FDA: 79930045608.12.54A0DAD Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf13.hostedemail.com (Postfix) with ESMTP id 122F12002C for ; Mon, 19 Sep 2022 20:57:23 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 3C32861ECF; Mon, 19 Sep 2022 20:57:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 04EE6C433D6; Mon, 19 Sep 2022 20:57:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1663621043; bh=7IVgxN4jKizV0N/1jpx39bak2NnAK31U23PaJaUNaVo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=xd/jE4qv5G2GKIlhUjgVOK4TRugup9Kxbo2h62YeeQvxfgVtEYsXEU2eCAvqu33Zb 2GmJIs5ldqc0OWF/SaL7OzkhvdEL4vSZnc9zE3Er4LVeVfSiaQ0zLXI1n4eBlaS/4h l8FCav0SV/ZDiA07kEdpXj+Ehi75h4vBSVY1FfUI= Date: Mon, 19 Sep 2022 13:57:10 -0700 From: Andrew Morton To: Dawei Li Cc: hch@lst.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: mmap lock holding assertion on remap_pfn_range Message-Id: <20220919135710.d52984bda33620f42d450010@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b="xd/jE4qv"; spf=pass (imf13.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1663621044; a=rsa-sha256; cv=none; b=N1NvMOiKDamE81RUYIFxg1O5uUg+0pl2T886z1DVzEW3+7wwn6h/gZCkp7M3Xhqxqh/oNa 2ZvBFoUD4ZcQE4R7CVj7QA7v8ziNaTDmakfBPKl8Z1eNzbDyGMO7ePJZiS6qNaJ6qojLzZ LxQsJ+k5tVuSyy+2Wc4RARfqo5Cg0oU= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1663621044; 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:dkim-signature; bh=5HWxnXSMmWeLCVG6N8JCi9SyzO3REhU8kWl1ApWzPSs=; b=ITEKHlXHfWueByALPm7pJco6nDoBmTuEZ8rkFavpi2hZhHcS9y1AW25EEaRsncSvaRQ6v0 Q/fTcDJ3xMUo4KY0XkWi8lHw1GQ2C6WnKRc9ENQcCfQn8aOn279fNcBrPIUAm/mmNxrSRI MJS5qm7cLMK2Dqn1LxzQVIrIFxL2Xmo= X-Rspam-User: X-Rspamd-Queue-Id: 122F12002C Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b="xd/jE4qv"; spf=pass (imf13.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Stat-Signature: d7fbm3e1hx8knb7y45p4rw5q4y47c1wt X-Rspamd-Server: rspam04 X-HE-Tag: 1663621043-122877 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: On Mon, 19 Sep 2022 23:47:32 +0800 Dawei Li wrote: > remap_pfn_range() creates/modifies the mapping between user virtual > address and physical address, the caller of which must hold mmap > writer lock to achieve access consistency of mapping. > > The callers fall into categories below: > 1) fops->mmap() implemented by driver > For this case, mmap_lock has been taken externally, the rule holds true. > > 2) Some arch codes do mapping on their own(vdso e.g.), rather than via > fops->mmap(). > > 3) Some driver codes do mapping into user address space, for some > reasons, the mapping is not implemented by fops->mmap(). > > For the last two cases, an explicit assertion must be made. Why "must" it be made? Are callers known to get this wrong? > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -2551,6 +2551,11 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr, > { > int err; > > + if (!vma->vm_mm) > + return -EINVAL; Can this happen? If so, under what circumstances? > + mmap_assert_write_locked(vma->vm_mm); > + > err = track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size)); > if (err) > return -EINVAL; > -- > 2.25.1