From patchwork Mon Jan 2 16:08:56 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 13086809 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DC91EC3DA7A for ; Mon, 2 Jan 2023 16:10:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232972AbjABQKR (ORCPT ); Mon, 2 Jan 2023 11:10:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55578 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236540AbjABQJ7 (ORCPT ); Mon, 2 Jan 2023 11:09:59 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D6063215 for ; Mon, 2 Jan 2023 08:09:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1672675752; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Sh73hBCrQns8aoevVV+OOnfi6R1HtUp1NLv5DeAjtKc=; b=WgybEYmh49GhZOS/zL+rI1LaVc2MXgfvdPFK7yKVQNx0fxV/z5G7MadflcnSppqdix5sRk YZRmjfXqrT0OYCdSQR3LkReQwcMC65K07ZXY590GV+zFusSAolY/627G+tX6/7Hu8ybcOJ 7Uhdr0CpRlLI7USr9xq7XYIwuVODstg= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-517-h6RgIbbbPnKtMqdUN9kSDg-1; Mon, 02 Jan 2023 11:09:09 -0500 X-MC-Unique: h6RgIbbbPnKtMqdUN9kSDg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 48408811E6E; Mon, 2 Jan 2023 16:09:08 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.193.209]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3D18D35455; Mon, 2 Jan 2023 16:09:06 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, David Hildenbrand , Andrew Morton , Arnd Bergmann , Greg Kroah-Hartman , Nicolas Pitre , Jens Axboe , Pavel Begunkov Subject: [PATCH mm-unstable v1 3/3] drivers/misc/open-dice: don't touch VM_MAYSHARE Date: Mon, 2 Jan 2023 17:08:56 +0100 Message-Id: <20230102160856.500584-4-david@redhat.com> In-Reply-To: <20230102160856.500584-1-david@redhat.com> References: <20230102160856.500584-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org A MAP_SHARED mapping always has VM_MAYSHARE set, and writable (VM_MAYWRITE) MAP_SHARED mappings have VM_SHARED set as well. To identify a MAP_SHARED mapping, it's sufficient to look at VM_MAYSHARE. We cannot have VM_MAYSHARE|VM_WRITE mappings without having VM_SHARED set. Consequently, current code will never actually end up clearing VM_MAYSHARE and that code is confusing, because nobody is supposed to mess with VM_MAYWRITE. Let's clean it up and restructure the code. No functional change intended. Cc: Arnd Bergmann Cc: Greg Kroah-Hartman Signed-off-by: David Hildenbrand --- drivers/misc/open-dice.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/drivers/misc/open-dice.c b/drivers/misc/open-dice.c index c61be3404c6f..9dda47b3fd70 100644 --- a/drivers/misc/open-dice.c +++ b/drivers/misc/open-dice.c @@ -90,15 +90,13 @@ static int open_dice_mmap(struct file *filp, struct vm_area_struct *vma) { struct open_dice_drvdata *drvdata = to_open_dice_drvdata(filp); - /* Do not allow userspace to modify the underlying data. */ - if ((vma->vm_flags & VM_WRITE) && (vma->vm_flags & VM_SHARED)) - return -EPERM; - - /* Ensure userspace cannot acquire VM_WRITE + VM_SHARED later. */ - if (vma->vm_flags & VM_WRITE) - vma->vm_flags &= ~VM_MAYSHARE; - else if (vma->vm_flags & VM_SHARED) + if (vma->vm_flags & VM_MAYSHARE) { + /* Do not allow userspace to modify the underlying data. */ + if (vma->vm_flags & VM_WRITE) + return -EPERM; + /* Ensure userspace cannot acquire VM_WRITE later. */ vma->vm_flags &= ~VM_MAYWRITE; + } /* Create write-combine mapping so all clients observe a wipe. */ vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);