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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 A151BC2D0EF for ; Thu, 26 Mar 2020 20:28:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7F58E2078C for ; Thu, 26 Mar 2020 20:28:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728871AbgCZU2V (ORCPT ); Thu, 26 Mar 2020 16:28:21 -0400 Received: from s3.sipsolutions.net ([144.76.43.62]:54802 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728765AbgCZU2K (ORCPT ); Thu, 26 Mar 2020 16:28:10 -0400 Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.93) (envelope-from ) id 1jHZ6j-00CGGW-CK; Thu, 26 Mar 2020 21:28:05 +0100 Message-ID: Subject: Re: [PATCH] kernel/taskstats: fix wrong nla type for {cgroup,task}stats policy From: Johannes Berg To: Andrew Morton , Yafang Shao Cc: bsingharora@gmail.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org, David Ahern , "David S.Miller" Date: Thu, 26 Mar 2020 21:28:03 +0100 In-Reply-To: <20200326130808.ccbacd6cba99a40326936fea@linux-foundation.org> References: <1585191042-9935-1-git-send-email-laoar.shao@gmail.com> <20200326130808.ccbacd6cba99a40326936fea@linux-foundation.org> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.34.4 (3.34.4-1.fc31) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2020-03-26 at 13:08 -0700, Andrew Morton wrote: > (cc's added) > > On Wed, 25 Mar 2020 22:50:42 -0400 Yafang Shao wrote: > > > After our server is upgraded to a newer kernel, we found that it > > continuesly print a warning in the kernel message. The warning is, > > [832984.946322] netlink: 'irmas.lc': attribute type 1 has an invalid length. > > > > irmas.lc is one of our container monitor daemons, and it will use > > CGROUPSTATS_CMD_GET to get the cgroupstats, that is similar with > > tools/accounting/getdelays.c. We can also produce this warning with > > getdelays. For example, after running bellow command > > $ ./getdelays -C /sys/fs/cgroup/memory > > then you can find a warning in dmesg, > > [61607.229318] netlink: 'getdelays': attribute type 1 has an invalid length. And looking at this ... well, that code is completely wrong? E.g. rc = send_cmd(nl_sd, id, mypid, TASKSTATS_CMD_GET, cmd_type, &tid, sizeof(__u32)); (cmd_type is one of TASKSTATS_CMD_ATTR_TGID, TASKSTATS_CMD_ATTR_PID) or it might do rc = send_cmd(nl_sd, id, mypid, CGROUPSTATS_CMD_GET, CGROUPSTATS_CMD_ATTR_FD, &cfd, sizeof(__u32)); so clearly it wants to produce a u32 attribute. But then static int send_cmd(int sd, __u16 nlmsg_type, __u32 nlmsg_pid, __u8 genl_cmd, __u16 nla_type, void *nla_data, int nla_len) { ... na = (struct nlattr *) GENLMSG_DATA(&msg); // this is still fine na->nla_type = nla_type; // this is also fine na->nla_len = nla_len + 1 + NLA_HDRLEN; // but this??? the nla_len of a netlink attribute should just be // the len ... what's NLA_HDRLEN doing here? this isn't nested // here we end up just reserving 1+NLA_HDRLEN too much space memcpy(NLA_DATA(na), nla_data, nla_len); // but then it anyway only fills the first nla_len bytes, which // is just like a regular attribute. msg.n.nlmsg_len += NLMSG_ALIGN(na->nla_len); // note that this is also wrong - it should be // += NLA_ALIGN(NLA_HDRLEN + nla_len) So really I think what happened here is precisely what we wanted - David's kernel patch caught the broken userspace tool. johannes