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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 D3625C3279B for ; Mon, 2 Jul 2018 22:16:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7622D258C9 for ; Mon, 2 Jul 2018 22:16:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="RxdpwI1d" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7622D258C9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=efficios.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753544AbeGBWQt (ORCPT ); Mon, 2 Jul 2018 18:16:49 -0400 Received: from mail.efficios.com ([167.114.142.138]:45428 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752715AbeGBWQr (ORCPT ); Mon, 2 Jul 2018 18:16:47 -0400 Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 6114F22FA7B; Mon, 2 Jul 2018 18:16:46 -0400 (EDT) Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10032) with ESMTP id iek0s1XL0nbb; Mon, 2 Jul 2018 18:16:45 -0400 (EDT) Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id D8DBC22FA78; Mon, 2 Jul 2018 18:16:45 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com D8DBC22FA78 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1530569805; bh=4/InqIB0XubKRaJKkCIpbp04m140OlVvwAIMI6YhQOA=; h=Date:From:To:Message-ID:MIME-Version; b=RxdpwI1dNbS/D7L2i222YT6AC9+bvjUsyl362QSIugDUzPcadBhgueJ1cRx6Lnd92 EAXbFkiYxUgpwda73FKPqU9MWTufdL7jhhmETM9fOpebk8w5tEmOrawVq/mfpNQvv/ P6CJST2ZNPj5BAoCxIOaYNzMog9Ed4CMIlxNC2iO/n7zcVOxRXb/E69nurQ2E6n+Jc rdjEXEZh66sk1xzeZlQcWy3KtAi5OrYt2/i4TBmzE4G+54ySUGvDFmuFDtbtqZumfA R7cWdIGhzxVO+9eKbLjoc+co3usqX7vcrED9ESWCbdvEYQfSvhh/PGPgo8EOBzCmni GTrXakzJUuK9g== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10026) with ESMTP id TVgdeTfWpgbp; Mon, 2 Jul 2018 18:16:45 -0400 (EDT) Received: from mail02.efficios.com (mail02.efficios.com [167.114.142.138]) by mail.efficios.com (Postfix) with ESMTP id BC07B22FA71; Mon, 2 Jul 2018 18:16:45 -0400 (EDT) Date: Mon, 2 Jul 2018 18:16:45 -0400 (EDT) From: Mathieu Desnoyers To: Linus Torvalds Cc: Thomas Gleixner , linux-kernel , linux-api , Peter Zijlstra , "Paul E. McKenney" , Boqun Feng , Andy Lutomirski , Dave Watson , Paul Turner , Andrew Morton , Russell King , Ingo Molnar , "H. Peter Anvin" , Andi Kleen , Chris Lameter , Ben Maurer , rostedt , Josh Triplett , Catalin Marinas , Will Deacon , Michael Kerrisk , Joel Fernandes Message-ID: <1051917568.10818.1530569805468.JavaMail.zimbra@efficios.com> In-Reply-To: References: <20180702204058.819-1-mathieu.desnoyers@efficios.com> <1307337131.10790.1530565424717.JavaMail.zimbra@efficios.com> <522686232.10814.1530569002544.JavaMail.zimbra@efficios.com> Subject: Re: [RFC PATCH for 4.18 1/2] rseq: use __u64 for rseq_cs fields, validate abort_ip < TASK_SIZE MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.142.138] X-Mailer: Zimbra 8.8.8_GA_2096 (ZimbraWebClient - FF52 (Linux)/8.8.8_GA_1703) Thread-Topic: rseq: use __u64 for rseq_cs fields, validate abort_ip < TASK_SIZE Thread-Index: WSd9lz113BMDj8YOtcgvhha5NoB8+A== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- On Jul 2, 2018, at 6:08 PM, Linus Torvalds torvalds@linux-foundation.org wrote: > On Mon, Jul 2, 2018 at 3:03 PM Mathieu Desnoyers > wrote: >> >> if (__get_user(ptr, &t->rseq->rseq_cs)) >> return -EINVAL; >> if (check_rseq_cs_padding(t)) >> return -EINVAL; > > Small nit. > > I think the _actual_ user access faults should return -EFAULT, and > then the *validation* checks should return -EINVAL. > > So when the "copy_from_user()" fails, that's -EFAULT, but when you > have (rseq_cs->start_ip >= TASK_SIZE), that's -EINVAL. Fair enough. > > That said, nothing actually cares or exposes the error number, I > think. Afaik, all the callers just check "did it work" or not. Indeed, it's a static function and callers just check for zero/nonzero. > > So this is more a "let's be consistent" than anything that matters. Allright, here is the function updated accordingly: static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) { struct rseq_cs __user *urseq_cs; unsigned long ptr; u32 __user *usig; u32 sig; int ret; ret = __get_user(ptr, &t->rseq->rseq_cs); if (ret) return ret; if (check_rseq_cs_padding(t)) return -EINVAL; if (!ptr) { memset(rseq_cs, 0, sizeof(*rseq_cs)); return 0; } urseq_cs = (struct rseq_cs __user *)ptr; if (copy_from_user(rseq_cs, urseq_cs, sizeof(*rseq_cs))) return -EFAULT; if (rseq_cs->start_ip >= TASK_SIZE || rseq_cs->start_ip + rseq_cs->post_commit_offset >= TASK_SIZE || rseq_cs->abort_ip >= TASK_SIZE || rseq_cs->version > 0) return -EINVAL; /* Check for overflow. */ if (rseq_cs->start_ip + rseq_cs->post_commit_offset < rseq_cs->start_ip) return -EINVAL; /* Ensure that abort_ip is not in the critical section. */ if (rseq_cs->abort_ip - rseq_cs->start_ip < rseq_cs->post_commit_offset) return -EINVAL; usig = (u32 __user *)(unsigned long)(rseq_cs->abort_ip - sizeof(u32)); ret = get_user(sig, usig); if (ret) return ret; if (current->rseq_sig != sig) { printk_ratelimited(KERN_WARNING "Possible attack attempt. Unexpected rseq signature 0x%x, expecting 0x%x (pid=%d, addr=%p).\n", sig, current->rseq_sig, current->pid, usig); return -EINVAL; } return 0; } Thanks for the feedback! Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com