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=-5.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, USER_AGENT_MUTT 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 1A7F4C43387 for ; Mon, 7 Jan 2019 17:11:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D80EC218AF for ; Mon, 7 Jan 2019 17:11:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="fOxssP5O" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727188AbfAGRLG (ORCPT ); Mon, 7 Jan 2019 12:11:06 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:45582 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726893AbfAGRLG (ORCPT ); Mon, 7 Jan 2019 12:11:06 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=uRkjJxjV/WgS4eUCRtQonlei5iRDdbZzr4L4TH1FUTo=; b=fOxssP5OmGTIGUjgLPVYndcBY QQm5rpMleiJWqcuX0VsokRrQ5bIq4wOK5QZIramzmb3MYUN95v0GK1pPL86gM2ke3ffXY552ltLro 0QcXrbL+wUSIZyiMMBUNehcg8p9CF/GVkhuX30K2x5zM6igHqvfqiU5Tv3xpFiSZeIiGvXlIHgLAt Hv6KdxWoFJo4AMYwyxJjeRrS019zLasmYE8REj+N7rsu6AyIkY7SbkidhLIDsv1U2b9zAWy3FX+9K HPS2xbhpLMTNfAlGgW8dodqVUnbKaE07L14YIGIA5VLBHuTc6Z7B9ODblAB2Vu6ZV+vdZJrAgSlrR tNgxbkWSg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1ggYQa-0007KA-L2; Mon, 07 Jan 2019 17:11:04 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 3B0F6201411A4; Mon, 7 Jan 2019 18:11:01 +0100 (CET) Date: Mon, 7 Jan 2019 18:11:01 +0100 From: Peter Zijlstra To: Kangjie Lu Cc: pakki001@umn.edu, Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched: fix a potential double-fetch bug in sched_copy_attr Message-ID: <20190107171101.GI14122@hirez.programming.kicks-ass.net> References: <20181225221648.70069-1-kjlu@umn.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181225221648.70069-1-kjlu@umn.edu> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 25, 2018 at 04:16:47PM -0600, Kangjie Lu wrote: > "uattr->size" is copied in from user space and checked. However, it is > copied in again after the security check. A malicious user may race to > change it. The fix checks if uattr->size is ever changed after the > check. > > Signed-off-by: Kangjie Lu > --- > + /* Sanity check if size was changed in user space */ > + if (attr->size != size) > + return -EINVAL; > + What perf_copy_attr() does (from whence we copied this code) is: attr->size = size; Would that not also fix things?