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=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 B237FC282DA for ; Wed, 17 Apr 2019 14:13:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 82E48204EC for ; Wed, 17 Apr 2019 14:13:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=brauner.io header.i=@brauner.io header.b="bKRxHrWR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732460AbfDQONO (ORCPT ); Wed, 17 Apr 2019 10:13:14 -0400 Received: from mail-wm1-f66.google.com ([209.85.128.66]:35872 "EHLO mail-wm1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728335AbfDQONN (ORCPT ); Wed, 17 Apr 2019 10:13:13 -0400 Received: by mail-wm1-f66.google.com with SMTP id h18so3825043wml.1 for ; Wed, 17 Apr 2019 07:13:12 -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=PaFbFt0d9eGXDX6m1UWhtov90KWEce3ZD19fSf2vJJ4=; b=bKRxHrWRrwnXEgsMDZ3ikLRkZn2bMwnbtO4WrhawvTWqA/CQJS9rhWJlvD8QJ2/cSA nd7XW/W/N6toy4ylRAqcs76U4TbIFT3+dr7ft6EKJYCt89zB2g/PSvf3hPHj8sar9713 VQAssExbc63Ixx2vrZxP/v9eRgU/maX/s+RjKwXS5K6iWbElGiM4sABvCDwG2Nh2M3TC ruxvUOgumtILOr9ANMwQVMD3dZtqPpqUzXFG7dewCQWmyt9OpKWm4uEfjsXUEWOXLJSA nr4erQbOU8vG4UADZhxOIWmxdwQRYuXuDklDIxpsDJlsh0ufCOkQqrW3ydbOKc7aYtWO 7CYA== 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=PaFbFt0d9eGXDX6m1UWhtov90KWEce3ZD19fSf2vJJ4=; b=EqBgSVdVTcfimM5ToZ2M++f5NFhQUnHCsWnNRxNMEcQCNpbcw8K3rCcXmUSU55mQuE l2GCUcAmvZCJBdcAbAYj/QVMWSzhuG7n7V5hfu50/AJcYnXPrOYoAXnogz3Po36WR7Kk OTJ0jznMSOTTEC3u4R+1DeQmReHNqtqe5Z0RXIhXUB7/5l0e2eyCQTq++scA2WKuZiND 1h63aILQflx92ODc6nnIKSCAvCCTVNipYMg2SwJcCLPjRamp2RDC/Lgon6dV4YsfwLzj beV0cDeAZoGRTAEOodtkUzSm9HYGCuxlYYcsH2Hkp/u614DtvmvAn1e+tENfmU4+wXzy mkFg== X-Gm-Message-State: APjAAAVsCQcyr/6bNzSFwk7SgzJMKELl/5MmensGBQYjMJKRkqMQ9dv+ Gm+yQpHl+cG9N54imukijb7vXg== X-Google-Smtp-Source: APXvYqyc0qIrgUl6FNV2C7xhYrs65TT3uNB5y3+5XhRDfYuZpVYJEjmEN/mJ6rSRmN6bgr45O0/qOg== X-Received: by 2002:a1c:3982:: with SMTP id g124mr30913738wma.25.1555510391643; Wed, 17 Apr 2019 07:13:11 -0700 (PDT) Received: from brauner.io ([185.197.132.10]) by smtp.gmail.com with ESMTPSA id k9sm81609241wru.55.2019.04.17.07.13.10 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 17 Apr 2019 07:13:10 -0700 (PDT) Date: Wed, 17 Apr 2019 16:13:09 +0200 From: Christian Brauner To: Oleg Nesterov Cc: Jann Horn , "Eric W. Biederman" , Arnd Bergmann , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: Re: [PATCH] signal: don't silently convert SI_USER signals to non-current pidfd Message-ID: <20190417141308.mpkkhy3sbw5e5hew@brauner.io> References: <20190330021232.191205-1-jannh@google.com> <20190408131315.GA24111@redhat.com> <20190417130336.i55vmf3x6cby2mvi@brauner.io> <20190417131602.GE32622@redhat.com> <20190417131904.qjkv2xuenhcsz36l@brauner.io> <20190417135002.GF32622@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190417135002.GF32622@redhat.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 17, 2019 at 03:50:03PM +0200, Oleg Nesterov wrote: > On 04/17, Christian Brauner wrote: > > > > On Wed, Apr 17, 2019 at 03:16:03PM +0200, Oleg Nesterov wrote: > > > On 04/17, Christian Brauner wrote: > > > > > > > > On Mon, Apr 08, 2019 at 03:13:16PM +0200, Oleg Nesterov wrote: > > > > > > > > > > but perhaps it should always fail, even if task_pid(current) == pid. > > > > > > > > > > sys_rt_sigqueueinfo() allows to send any siginfo to yourself, but this is only needed > > > > > for checkpoint/restart. > > > > > > > > Yes, that's why this was added. I would leave it in exactly because of > > > > checkpoint/restart. > > > > > > I don't understand... > > > > > > c/r doesn't need this "feature" in pidfd_send_signal(), so it can be removed. > > > But, > > > > Just out of curiosity: in what sense? They don't need it since they have > > other ways of doing this > > Yes. The restarting process needs to "restore" the pending signals, including the > signals with si_code >= 0. It does this using tgsigqueueinfo() and that is why we > allow this if the signal sent to itself. > > So criu simply doesn't need pidfd_send_signal() to do this. And at the same time, > > > or they *can't* use it for some other reason > > Yes again. pidfd_send_signal() does kill_pid_info(), so it can't be used to restore > the "per-thread" task->pending signals. In the future pidfd_send_signal() will gain the flag PIDFD_SIGNAL_THREAD. Jann and I already have a patch for this but we're holding off until the need arises. Christian