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=-12.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,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 6C56CC4361B for ; Sun, 20 Dec 2020 04:49:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 398152313B for ; Sun, 20 Dec 2020 04:49:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727211AbgLTEsq (ORCPT ); Sat, 19 Dec 2020 23:48:46 -0500 Received: from mail.efficios.com ([167.114.26.124]:47556 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726997AbgLTEsp (ORCPT ); Sat, 19 Dec 2020 23:48:45 -0500 Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id C7E622E839A; Sat, 19 Dec 2020 23:48:04 -0500 (EST) Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id pw1zU6eRf8YH; Sat, 19 Dec 2020 23:48:04 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 675252E82A4; Sat, 19 Dec 2020 23:48:04 -0500 (EST) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 675252E82A4 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1608439684; bh=Lk9DAUYi457LuXbQYMHGuDJkzWjmmcJLZglkXK6gdHw=; h=To:From:Message-ID:Date:MIME-Version; b=c6qMSWj/rXRgc+w9P5B9j/pUvKf1WrVNVIYvgpXZs81z3aETr/hxYWMc79qxO/JSd TkWX9JDN3jtfIF8pXEGRwDoq9zUcjSekmTK7Z4lOcduLbKDJozDIInq/oH6kZGSk9g RuGudvFqshw5ZSAW0ZfT5AjkEpduEjbpKrHOMFIHKdNTY8lUWvLh9HoCAafwP4XWdN DQsVGpYflypPBFd2ZMRRVfG1kOT53tfH6al8GfuOkDsOtYJtuJIvr84o2mZ7nni4tu XU+Exo3qztVl+/sR3MQWF/b6keZ9K1edV1J9fISQNim8ai7w7tAnPect5u8NwSIDXz KjvGOLnKbzryQ== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id HqLyW-hjsYlV; Sat, 19 Dec 2020 23:48:04 -0500 (EST) Received: from [10.0.0.213] (192-222-157-6.qc.cable.ebox.net [192.222.157.6]) by mail.efficios.com (Postfix) with ESMTPSA id 315AE2E82A3; Sat, 19 Dec 2020 23:48:04 -0500 (EST) Subject: Re: [RFC PATCH] ptrace: make ptrace() fail if the tracee changed its pid unexpectedly To: Oleg Nesterov , Pedro Alves Cc: "Eric W. Biederman" , Andrew Morton , Eugene Syromiatnikov , Jan Kratochvil , Linus Torvalds , Mathieu Desnoyers , Michael Kerrisk , linux-kernel@vger.kernel.org References: <20201217142931.GA8865@redhat.com> <875z50roia.fsf@x220.int.ebiederm.org> <20201219193313.GB9539@redhat.com> From: Simon Marchi Message-ID: Date: Sat, 19 Dec 2020 23:48:03 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20201219193313.GB9539@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-12-19 2:33 p.m., Oleg Nesterov wrote: > OOPS! Sorry Simon, yes I forgot to add reported-by. Andrew, or Eric, if > you take this patch, could you also add > > Reported-by: Simon Marchi I tried the original reproducer on a patched kernel, and it looks good. GDB's behavior is still not super clean when this situation happens: a PTRACE_GETREGS on the (disappeared) leader now fails with ESRCH (that's what we want), and that interrupts the "continue" command and unexpectedly brings back the prompt while leaving the other thread running. But that is all logic that will have to be fixed inside GDB. So, feel free to add Acked-by: Simon Marchi too. Thanks! Simon