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_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 E4440C76191 for ; Thu, 18 Jul 2019 13:21:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC15B2173E for ; Thu, 18 Jul 2019 13:21:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="CxBHd/RX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390497AbfGRNVR (ORCPT ); Thu, 18 Jul 2019 09:21:17 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:37544 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390356AbfGRNVR (ORCPT ); Thu, 18 Jul 2019 09:21:17 -0400 Received: by mail-pg1-f193.google.com with SMTP id i70so2156668pgd.4 for ; Thu, 18 Jul 2019 06:21:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=VxIj7dTtj9q2yI2i58D0deKruMz+tclfFnwAic5jf9E=; b=CxBHd/RXkwlY3wwcWK9hjWpkRNa0WCIATIrV0fwaIBDVz73eRA425pTQu+L2AcyGKA lO6WF9C01QsmVGQCYbsCG/JqprRFd9wZgBmtu6El5pWbZ0r4u1jArEtFSsz8WzVYj2oO My8eo0wVW3fYzE3SiwsCS+tdc/l8SOqOGVyYg= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=VxIj7dTtj9q2yI2i58D0deKruMz+tclfFnwAic5jf9E=; b=rjooPjZgRSm+SGNATCvjH50WcCzq7HkqyzL4pY9JStp7qa3VLQQYHrslUfAYVj/14n 7+PmCv/5KUhH04y4dcf/0jBbq+An1GRojfJoH7TWQyQfChhXjvBUcZp3uNLhsP/BrwFd HmkC8ViymTp4JiBrnCJbZMZFfETpyCMyjs5XEstsTTPubB4N2QwnY02wqsl+KrWG9GeZ vtvp6h3DC0Hpo0JUf/XRlBiz6d+lkqkuYVwbPYKWTvdnlGwBFdrbWKZR9m9OJcKyOZPP KUaKQQZ9OpKVH4xBv6lkY6c27fqYM9mrP4dmFm6Qv40uI1w1UabQrSUyGvUwdvHIloro ZEcA== X-Gm-Message-State: APjAAAVavgyOiAj6l/PdNoc2CDDFPjyrdLs2vnBHc4xjS0Ho/byJ4yzH 1zF4epxucbm2vkrVkLyHmmY= X-Google-Smtp-Source: APXvYqyXj8OhcWahZPu5wg4U4oMONsYLM3+qU7fC4rjCpXXlrXhjNWKXukegETCztH0gsrCQZ0Rt0g== X-Received: by 2002:a63:494d:: with SMTP id y13mr48528915pgk.109.1563456076261; Thu, 18 Jul 2019 06:21:16 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id w2sm21898289pgc.32.2019.07.18.06.21.15 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Thu, 18 Jul 2019 06:21:15 -0700 (PDT) Date: Thu, 18 Jul 2019 09:21:14 -0400 From: Joel Fernandes To: Peter Zijlstra Cc: Vegard Nossum , tglx@linutronix.de, bp@alien8.de, mingo@kernel.org, rostedt@goodmis.org, luto@kernel.org, torvalds@linux-foundation.org, hpa@zytor.com, dave.hansen@linux.intel.com, jgross@suse.com, linux-kernel@vger.kernel.org, zhe.he@windriver.com, devel@etsukata.com Subject: Re: [PATCH] stacktrace: Force USER_DS for stack_trace_save_user() Message-ID: <20190718132114.GB116002@google.com> References: <20190711114054.406765395@infradead.org> <4c71e14d-3a32-c3bb-8e3b-6e5100853192@oracle.com> <20190717080725.GK3402@hirez.programming.kicks-ass.net> <20190718085754.GM3402@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190718085754.GM3402@hirez.programming.kicks-ass.net> 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 Thu, Jul 18, 2019 at 10:57:54AM +0200, Peter Zijlstra wrote: > On Wed, Jul 17, 2019 at 10:09:45AM +0200, Vegard Nossum wrote: > > On 7/17/19 10:07 AM, Peter Zijlstra wrote: > > > > Does something like the below help? > > > Yes. > > Thanks! > > --- > Subject: stacktrace: Force USER_DS for stack_trace_save_user() > From: Peter Zijlstra > Date: Thu Jul 18 10:47:47 CEST 2019 > > When walking userspace stacks, we should set USER_DS, otherwise > access_ok() will not function as expected. > > Reported-by: Vegard Nossum > Tested-by: Vegard Nossum > Reported-by: Eiichi Tsukata > Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Joel Fernandes (Google) thanks, - Joel > --- > --- a/kernel/stacktrace.c > +++ b/kernel/stacktrace.c > @@ -226,12 +226,17 @@ unsigned int stack_trace_save_user(unsig > .store = store, > .size = size, > }; > + mm_segment_t fs; > > /* Trace user stack if not a kernel thread */ > if (current->flags & PF_KTHREAD) > return 0; > > + fs = get_fs(); > + set_fs(USER_DS); > arch_stack_walk_user(consume_entry, &c, task_pt_regs(current)); > + set_fs(fs); > + > return c.len; > } > #endif