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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 D781EC433E6 for ; Mon, 4 Jan 2021 13:02:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 89F6921D93 for ; Mon, 4 Jan 2021 13:02:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726762AbhADNCb (ORCPT ); Mon, 4 Jan 2021 08:02:31 -0500 Received: from mail.kernel.org ([198.145.29.99]:60098 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725830AbhADNC3 (ORCPT ); Mon, 4 Jan 2021 08:02:29 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id E2B86207B1; Mon, 4 Jan 2021 13:01:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1609765308; bh=yzCJ7gttoK052lq2RlNPBiUyeQ/F04H5GVCbPkcutFs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=0BOqU0WPC4c1AgvQ+1KMCIzTCyQi7N4B1JrrcoX3MVgI86GgQisuNLQlUmZ9T4GQ9 55vGn45Gp+Lv7OK4SCbXb9qKJoClMHPhxknhAbSEu7CMwZ3YzxwnL+CcVZVALWlgRg PzQRoua1gKktT3BXsRiQ5KqM4yIbC8pcVY96KmNk= Date: Mon, 4 Jan 2021 14:03:14 +0100 From: Greg Kroah-Hartman To: Wen Yang Cc: Sasha Levin , Xunlei Pang , linux-kernel@vger.kernel.org, Christian Brauner , Linus Torvalds , Jann Horn , Oleg Nesterov , Arnd Bergmann , "Eric W. Biederman" , Kees Cook , Thomas Gleixner , David Howells , "Michael Kerrisk (man-pages)" , Andy Lutomirsky , Andrew Morton , Aleksa Sarai , Al Viro , stable@vger.kernel.org Subject: Re: [PATCH 01/10] clone: add CLONE_PIDFD Message-ID: References: <20201203183204.63759-1-wenyang@linux.alibaba.com> <20201203183204.63759-2-wenyang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201203183204.63759-2-wenyang@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 04, 2020 at 02:31:55AM +0800, Wen Yang wrote: > From: Christian Brauner > > [ Upstream commit b3e5838252665ee4cfa76b82bdf1198dca81e5be ] > > This patchset makes it possible to retrieve pid file descriptors at > process creation time by introducing the new flag CLONE_PIDFD to the > clone() system call. Linus originally suggested to implement this as a > new flag to clone() instead of making it a separate system call. As > spotted by Linus, there is exactly one bit for clone() left. > > CLONE_PIDFD creates file descriptors based on the anonymous inode > implementation in the kernel that will also be used to implement the new > mount api. They serve as a simple opaque handle on pids. Logically, > this makes it possible to interpret a pidfd differently, narrowing or > widening the scope of various operations (e.g. signal sending). Thus, a > pidfd cannot just refer to a tgid, but also a tid, or in theory - given > appropriate flag arguments in relevant syscalls - a process group or > session. A pidfd does not represent a privilege. This does not imply it > cannot ever be that way but for now this is not the case. > > A pidfd comes with additional information in fdinfo if the kernel supports > procfs. The fdinfo file contains the pid of the process in the callers > pid namespace in the same format as the procfs status file, i.e. "Pid:\t%d". > > As suggested by Oleg, with CLONE_PIDFD the pidfd is returned in the > parent_tidptr argument of clone. This has the advantage that we can > give back the associated pid and the pidfd at the same time. > > To remove worries about missing metadata access this patchset comes with > a sample program that illustrates how a combination of CLONE_PIDFD, and > pidfd_send_signal() can be used to gain race-free access to process > metadata through /proc/. The sample program can easily be > translated into a helper that would be suitable for inclusion in libc so > that users don't have to worry about writing it themselves. > > Suggested-by: Linus Torvalds > Signed-off-by: Christian Brauner > Co-developed-by: Jann Horn > Signed-off-by: Jann Horn > Reviewed-by: Oleg Nesterov > Cc: Arnd Bergmann > Cc: "Eric W. Biederman" > Cc: Kees Cook > Cc: Thomas Gleixner > Cc: David Howells > Cc: "Michael Kerrisk (man-pages)" > Cc: Andy Lutomirsky > Cc: Andrew Morton > Cc: Aleksa Sarai > Cc: Linus Torvalds > Cc: Al Viro > Cc: # 4.9.x > (clone: fix up cherry-pick conflicts for b3e583825266) > Signed-off-by: Wen Yang > --- > include/linux/pid.h | 1 + > include/uapi/linux/sched.h | 1 + > kernel/fork.c | 119 +++++++++++++++++++++++++++++++++++++++++++-- > 3 files changed, 117 insertions(+), 4 deletions(-) > > diff --git a/include/linux/pid.h b/include/linux/pid.h > index 97b745d..7599a78 100644 > --- a/include/linux/pid.h > +++ b/include/linux/pid.h > @@ -73,6 +73,7 @@ struct pid_link > struct hlist_node node; > struct pid *pid; > }; > +extern const struct file_operations pidfd_fops; > > static inline struct pid *get_pid(struct pid *pid) > { > diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h > index 5f0fe01..ed6e31d 100644 > --- a/include/uapi/linux/sched.h > +++ b/include/uapi/linux/sched.h > @@ -9,6 +9,7 @@ > #define CLONE_FS 0x00000200 /* set if fs info shared between processes */ > #define CLONE_FILES 0x00000400 /* set if open files shared between processes */ > #define CLONE_SIGHAND 0x00000800 /* set if signal handlers and blocked signals shared */ > +#define CLONE_PIDFD 0x00001000 /* set if a pidfd should be placed in parent */ > #define CLONE_PTRACE 0x00002000 /* set if we want to let tracing continue on the child too */ > #define CLONE_VFORK 0x00004000 /* set if the parent wants the child to wake it up on mm_release */ > #define CLONE_PARENT 0x00008000 /* set if we want to have the same parent as the cloner */ > diff --git a/kernel/fork.c b/kernel/fork.c > index b64efec..076297a 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -11,7 +11,22 @@ > * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' > */ > > +#include > #include > +#if 0 > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +>>>>>>> b3e58382... clone: add CLONE_PIDFD > +#endif That looks odd :( Can you please refresh this patch series, and make sure it is correct and resend it? thanks, greg k-h