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=-10.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 BBA63C433E0 for ; Mon, 27 Jul 2020 16:13:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 91AEF20672 for ; Mon, 27 Jul 2020 16:13:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730469AbgG0QN0 (ORCPT ); Mon, 27 Jul 2020 12:13:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54696 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727975AbgG0QN0 (ORCPT ); Mon, 27 Jul 2020 12:13:26 -0400 Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [IPv6:2002:c35c:fd02::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 714A7C061794; Mon, 27 Jul 2020 09:13:25 -0700 (PDT) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1k05kd-003kkL-3j; Mon, 27 Jul 2020 16:13:19 +0000 Date: Mon, 27 Jul 2020 17:13:19 +0100 From: Al Viro To: Nick Bowler Cc: linux-kernel@vger.kernel.org, "David S. Miller" , netdev@vger.kernel.org Subject: [PATCH] Re: PROBLEM: cryptsetup fails to unlock drive in 5.8-rc6 (regression) Message-ID: <20200727161319.GH794331@ZenIV.linux.org.uk> References: <20200723155101.pnezpo574ot4qkzx@atlas.draconx.ca> <20200727160554.GG794331@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200727160554.GG794331@ZenIV.linux.org.uk> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 27, 2020 at 05:05:54PM +0100, Al Viro wrote: > On Thu, Jul 23, 2020 at 11:51:01AM -0400, Nick Bowler wrote: > > Hi, > > > > After installing Linux 5.8-rc6, it seems cryptsetup can no longer > > open LUKS volumes. Regardless of the entered passphrase (correct > > or otherwise), the result is a very unhelpful "Keyslot open failed." > > message. > > > > On the kernels which fail, I also noticed that the cryptsetup > > benchmark command appears to not be able to determine that any > > ciphers are available (output at end of message), possibly for > > the same reason. > > > > Bisected to the following commit, which suggests a problem specific > > to compat userspace (this is amd64 kernel). I tested both ia32 and > > x32 userspace to confirm the problem. Reverting this commit on top > > of 5.8-rc6 resolves the issue. > > > > Looking at strace output the failing syscall appears to be: > > > > sendmsg(8, {msg_name=NULL, msg_namelen=0, > > msg_iov=[{iov_base=..., iov_len=512}], msg_iovlen=1, > > msg_control=[{cmsg_len=16, cmsg_level=SOL_ALG, > > cmsg_type=0x3}, {cmsg_len=32, cmsg_level=SOL_ALG, > > cmsg_type=0x2}], msg_controllen=48, msg_flags=0}, 0) > > = -1 EINVAL (Invalid argument) > > Huh? Just in case - could you verify that on the kernel with that > commit reverted the same sendmsg() succeeds? Oh, fuck... Please see if the following fixes your reproducer; the braino is, of course, that instead of fetching ucmsg->cmsg_len into ucmlen we read the entire thing into cmsg. Other uses of ucmlen had been replaced with cmsg.cmsg_len; this one was missed. Signed-off-by: Al Viro --- diff --git a/net/compat.c b/net/compat.c index 5e3041a2c37d..434838bef5f8 100644 --- a/net/compat.c +++ b/net/compat.c @@ -202,7 +202,7 @@ int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg, struct sock *sk, /* Advance. */ kcmsg = (struct cmsghdr *)((char *)kcmsg + tmp); - ucmsg = cmsg_compat_nxthdr(kmsg, ucmsg, ucmlen); + ucmsg = cmsg_compat_nxthdr(kmsg, ucmsg, cmsg.cmsg_len); } /*