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=-13.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,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 22FB7C43441 for ; Sat, 17 Nov 2018 09:00:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E866C2077C for ; Sat, 17 Nov 2018 09:00:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E866C2077C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.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 S1726153AbeKQTQR (ORCPT ); Sat, 17 Nov 2018 14:16:17 -0500 Received: from mx1.redhat.com ([209.132.183.28]:54734 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725850AbeKQTQR (ORCPT ); Sat, 17 Nov 2018 14:16:17 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E567083F3F; Sat, 17 Nov 2018 09:00:16 +0000 (UTC) Received: from krava (ovpn-204-61.brq.redhat.com [10.40.204.61]) by smtp.corp.redhat.com (Postfix) with SMTP id B4E8C17AD2; Sat, 17 Nov 2018 09:00:14 +0000 (UTC) Date: Sat, 17 Nov 2018 10:00:10 +0100 From: Jiri Olsa To: Arnaldo Carvalho de Melo Cc: Jiri Olsa , Krister Johansen , lkml , Ingo Molnar , Namhyung Kim , Alexander Shishkin , Peter Zijlstra Subject: Re: [PATCH] perf tools: Restore proper cwd on return from mnt ns Message-ID: <20181117090010.GP9600@krava> References: <20181101170001.30019-1-jolsa@kernel.org> <20181116183143.GD18319@kernel.org> <20181116184245.GE18319@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181116184245.GE18319@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Sat, 17 Nov 2018 09:00:17 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 16, 2018 at 10:42:45AM -0800, Arnaldo Carvalho de Melo wrote: > Em Fri, Nov 16, 2018 at 10:31:43AM -0800, Arnaldo Carvalho de Melo escreveu: > > Em Thu, Nov 01, 2018 at 06:00:01PM +0100, Jiri Olsa escreveu: > > > When reporting on 'record' server we try to retrieve/use > > > the mnt namespace of the profiled tasks. We use following > > > API with cookie to hold the return namespace, roughly: > > > > > > nsinfo__mountns_enter(struct nsinfo *nsi, struct nscookie *nc) > > > setns(newns, 0); > > > ... > > > new ns related open.. > > > ... > > > nsinfo__mountns_exit(struct nscookie *nc) > > > setns(nc->oldns) > > > > > > Once finished we setns to old namespace, which also sets the > > > current working directory (cwd) to "/", trashing the cwd we had. > > > > > > This is mostly fine, because we use absolute paths almost everywhere, > > > but it screws up perf diff: > > > > > > # perf diff > > > failed to open perf.data: No such file or directory (try 'perf record' first) > > > ... > > > > > > Adding the current working directory to be part of the cookie > > > and restoring it in the nsinfo__mountns_exit call. > > > > > Cc: Krister Johansen > > > Fixes: 843ff37bb59e ("perf symbols: Find symbols in different mount namespace") > > > Link: http://lkml.kernel.org/n/tip-zg3vz7kjr86cco7lo91v8yhj@git.kernel.org > > > Signed-off-by: Jiri Olsa > > > --- > > > tools/perf/util/namespaces.c | 18 ++++++++++++++++-- > > > tools/perf/util/namespaces.h | 1 + > > > 2 files changed, 17 insertions(+), 2 deletions(-) > > > > > > diff --git a/tools/perf/util/namespaces.c b/tools/perf/util/namespaces.c > > > index cf8bd123cf73..fb0458b7e6aa 100644 > > > --- a/tools/perf/util/namespaces.c > > > +++ b/tools/perf/util/namespaces.c > > > @@ -18,6 +18,7 @@ > > > #include > > > #include > > > #include > > > +#include > > > > > > struct namespaces *namespaces__new(struct namespaces_event *event) > > > { > > > @@ -186,6 +187,7 @@ void nsinfo__mountns_enter(struct nsinfo *nsi, > > > char curpath[PATH_MAX]; > > > int oldns = -1; > > > int newns = -1; > > > + char *oldcwd = NULL; > > > > > > if (nc == NULL) > > > return; > > > @@ -199,9 +201,13 @@ void nsinfo__mountns_enter(struct nsinfo *nsi, > > > if (snprintf(curpath, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX) > > > return; > > > > > > + oldcwd = get_current_dir_name(); > > > + if (!oldcwd) > > > + return; > > > + > > > oldns = open(curpath, O_RDONLY); > > > if (oldns < 0) > > > - return; > > > + goto errout; > > > > > > newns = open(nsi->mntns_path, O_RDONLY); > > > if (newns < 0) > > > @@ -210,11 +216,14 @@ void nsinfo__mountns_enter(struct nsinfo *nsi, > > > if (setns(newns, CLONE_NEWNS) < 0) > > > goto errout; > > > > > > + nc->oldcwd = oldcwd; > > > nc->oldns = oldns; > > > nc->newns = newns; > > > return; > > > > > > errout: > > > + if (oldcwd) > > > + free(oldcwd); right, ok > > > > Applied, and while at it I removed the needless if in the above two > > lines. > > > > > if (oldns > -1) > > > close(oldns); > > > if (newns > -1) > > > @@ -223,11 +232,16 @@ void nsinfo__mountns_enter(struct nsinfo *nsi, > > > > > > void nsinfo__mountns_exit(struct nscookie *nc) > > > { > > > - if (nc == NULL || nc->oldns == -1 || nc->newns == -1) > > > + if (nc == NULL || nc->oldns == -1 || nc->newns == -1 || !nc->oldcwd) > > > return; > > > > > > setns(nc->oldns, CLONE_NEWNS); > > > > > > + if (nc->oldcwd) { > > > + WARN_ON_ONCE(chdir(nc->oldcwd)); > > > + free(nc->oldcwd); > > > + } > > > + > > Also changed the above to zfree(&nc->oldcwd) as this is in a struct > member, that is not freed by the freeing caller > (nsinfo__mountns_exit()), to avoid later possible use-after-free (I > haven't checked if it _actually_ happens with the current codebase, but > it could) also to match the following block, where the resource is > released and then the handler is invalidated. great, thanks jirka