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=-3.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_NEOMUTT 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 B0876C04E53 for ; Wed, 15 May 2019 14:49:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 804A020873 for ; Wed, 15 May 2019 14:49:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=brauner.io header.i=@brauner.io header.b="gbthNhor" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728326AbfEOOtd (ORCPT ); Wed, 15 May 2019 10:49:33 -0400 Received: from mail-ed1-f67.google.com ([209.85.208.67]:39840 "EHLO mail-ed1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727341AbfEOOtc (ORCPT ); Wed, 15 May 2019 10:49:32 -0400 Received: by mail-ed1-f67.google.com with SMTP id e24so206627edq.6 for ; Wed, 15 May 2019 07:49:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=brauner.io; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=oKULkZSRwqaiQxP7TL4UYPkN+uTDZlr88Vcbz3QuA1I=; b=gbthNhordMIYVnTy317gMGg6f/dfC5iQgBxjq6Pg3jScMLdLI0Vq4OcwB79UHvgEgC U1AgURPKc8JVgJXOo0PlK1NBODmUH4LG0c3iQOkHAxHOhxIV3lZFFgtryVL471yH2yaW C3klxUr1MKghIvHXbdcitmAziIPiCtbEw5zo2mlbo+BrqzIdRMNr8g8Hd8yvC+RFkoND 3U7iWRnczi1gGSuo/hShIfYUEndn7uxrlNKw8BfZPzT5nVaY90n0JScdqCfYtxsar1cX tdmjNXgvyrjanexmF/91CzUGx8XsXtV3i+hqAVIqFgPvc7YR3o00EzVeVZB9N4qN/XJl yDqg== 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=oKULkZSRwqaiQxP7TL4UYPkN+uTDZlr88Vcbz3QuA1I=; b=GpHspgZtxRjC12sG84vaxRLRVaa64M86jDPmQ2BArf2BdSdqTCav1P/hvCiVsn4G22 ApWtS+PMyMnNYcX5PVm4aLgkd3fdxJSBmdXKTKA3hWtTaS7JEET9Pm/mQUrQ1n/6mHYd WhkMG9EfLC1Qi0QJW/PTZCu2ViNNS8iLsWLtf8LizioHO508nibn6LTN7tkvq2YOOddh AvgAG9lzk6KWz3bJMG3doTWgSazVVuE1C4IHMBVXHOe7hcG1r+SYQAZl0E8zyxRfnUrw IBxdjD+LJrmW2+0/0wGAP0Q9u7StvO1QVKIvISjmkm7EJ9JQxeV4UeOnd89OfyYtrt+4 +yTg== X-Gm-Message-State: APjAAAXZTP1WtduH9I458xKKlfB6kqN8Z1CfyUZ2D7nYg0AgCUFMQ+3H AHSwDbda0ZaziDpcr1/JnJZ8lg== X-Google-Smtp-Source: APXvYqwtuLZTJzieEZtQQr5tQJZGg6NHI/b45QGiYK/CmzqPYIKTHEi4eYHx8oYap2x4c/tmYGlpdA== X-Received: by 2002:a50:8eb6:: with SMTP id w51mr43141017edw.34.1557931770356; Wed, 15 May 2019 07:49:30 -0700 (PDT) Received: from brauner.io ([178.19.218.101]) by smtp.gmail.com with ESMTPSA id a32sm873557ede.76.2019.05.15.07.49.29 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 15 May 2019 07:49:29 -0700 (PDT) Date: Wed, 15 May 2019 16:49:28 +0200 From: Christian Brauner To: Oleg Nesterov Cc: jannh@google.com, viro@zeniv.linux.org.uk, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, arnd@arndb.de, dhowells@redhat.com, akpm@linux-foundation.org, cyphar@cyphar.com, ebiederm@xmission.com, elena.reshetova@intel.com, keescook@chromium.org, luto@amacapital.net, luto@kernel.org, tglx@linutronix.de, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH 1/2] pid: add pidfd_open() Message-ID: <20190515144927.f2yxyi6w6lhn3xx7@brauner.io> References: <20190515100400.3450-1-christian@brauner.io> <20190515143857.GB18892@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190515143857.GB18892@redhat.com> User-Agent: NeoMutt/20180716 Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Wed, May 15, 2019 at 04:38:58PM +0200, Oleg Nesterov wrote: > On 05/15, Christian Brauner wrote: > > > > +SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags) > > +{ > > + int fd, ret; > > + struct pid *p; > > + struct task_struct *tsk; > > + > > + if (flags) > > + return -EINVAL; > > + > > + if (pid <= 0) > > + return -EINVAL; > > + > > + p = find_get_pid(pid); > > + if (!p) > > + return -ESRCH; > > + > > + rcu_read_lock(); > > + tsk = pid_task(p, PIDTYPE_PID); > > You do not need find_get_pid() before rcu_lock and put_pid() at the end. > You can just do find_vpid() under rcu_read_lock(). Will do. > > > + if (!tsk) > > + ret = -ESRCH; > > + else if (unlikely(!thread_group_leader(tsk))) > > + ret = -EINVAL; > > it seems that you can do a single check > > tsk = pid_task(p, PIDTYPE_TGID); > if (!tsk) > ret = -ESRCH; > > this even looks more correct if we race with exec changing the leader. The logic here being that you can only reach the thread_group leader from struct pid if PIDTYPE_PID == PIDTYPE_TGID for this struct pid? Thanks, Oleg. Christian