From patchwork Fri Dec 20 23:27:49 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sargun Dhillon X-Patchwork-Id: 11306519 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B7A69139A for ; Fri, 20 Dec 2019 23:27:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 83A622082E for ; Fri, 20 Dec 2019 23:27:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=sargun.me header.i=@sargun.me header.b="ijOzIAtj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726539AbfLTX1w (ORCPT ); Fri, 20 Dec 2019 18:27:52 -0500 Received: from mail-il1-f196.google.com ([209.85.166.196]:44922 "EHLO mail-il1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726470AbfLTX1w (ORCPT ); Fri, 20 Dec 2019 18:27:52 -0500 Received: by mail-il1-f196.google.com with SMTP id z12so9321524iln.11 for ; Fri, 20 Dec 2019 15:27:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sargun.me; s=google; h=date:from:to:cc:subject:message-id:mime-version:content-disposition :user-agent; bh=ZUqxZgsASKzXQm2M4tklMIaw/3yZpJ0Kn5yfMnOfzzY=; b=ijOzIAtjctijgjeGKCJEIw69D+tQ8KJziesTnkjrghSsh26P9NishfxV+v33x4HzAN M2qWhV2qzQhj3ofKKWr/SoDVbHNHHWbRoxpD1ie5hIoH09+/g0LNokwv07dK11OPFruH /Um6LDMKgFwgPdDrMF/HBA7U6Y3RJ2/dpyCoo= 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:mime-version :content-disposition:user-agent; bh=ZUqxZgsASKzXQm2M4tklMIaw/3yZpJ0Kn5yfMnOfzzY=; b=EvRmg+8E+Y9CkPYe21hb5juOEV1n+0SXZ8/V1HKiycrpyxNK4UTSOnIrczfcdLo8in tR8DLXG/B+04PLevXlHWPx9mccDB6MLv7EDH+pqorw9rxXrgdys5Ch/xYTYwg0nokfkj fd1iW1Q+wGFsCUWhenP0sZgVQr5f2tNCvBtV0ceGT+WKJRMqUkTcsbjRhujA+L0u4gCb 2Otn5EUnyjecQWHFpLE3aDSYHzBvz2+h7ha8DIHjljE1BBxSz2AWU1+y8pFS2Z3gF9IJ T7NDZbca25D9OaukdlhTdY+naQX83zeIXyTkFpp9lc1+y3OtkgkqsBTKP/lvb386IHbT 8bEQ== X-Gm-Message-State: APjAAAW2QawqoZTglnUTyrESIhxoEY3XuvKD4IO8Db8Wi/F0AfOwLbCu n2Aw48zWgeBO2ZVaEjt9KVZ8SQ== X-Google-Smtp-Source: APXvYqx6DJF0HdWYtUyZuIY8x9eKPbK1WdvoFdpSid5cjGP9+CD+I3Cilcm+4gQY7hzUU6i6jTw7HA== X-Received: by 2002:a92:cb10:: with SMTP id s16mr14563659ilo.176.1576884471551; Fri, 20 Dec 2019 15:27:51 -0800 (PST) Received: from ircssh-2.c.rugged-nimbus-611.internal (80.60.198.104.bc.googleusercontent.com. [104.198.60.80]) by smtp.gmail.com with ESMTPSA id m90sm1462397ilh.56.2019.12.20.15.27.51 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 20 Dec 2019 15:27:51 -0800 (PST) Date: Fri, 20 Dec 2019 23:27:49 +0000 From: Sargun Dhillon To: linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: tycho@tycho.ws, jannh@google.com, cyphar@cyphar.com, christian.brauner@ubuntu.com, oleg@redhat.com, luto@amacapital.net, viro@zeniv.linux.org.uk, gpascutto@mozilla.com, ealvarez@mozilla.com, fweimer@redhat.com, jld@mozilla.com, arnd@arndb.de Subject: [PATCH v5 0/3] Add pidfd_getfd syscall Message-ID: <20191220232746.GA20215@ircssh-2.c.rugged-nimbus-611.internal> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org This patchset introduces a mechanism (pidfd_getfd syscall) to get file descriptors from other processes via pidfd. Although this can be achieved using SCM_RIGHTS, and parasitic code injection, this offers a more straightforward mechanism, with less overhead and complexity. The process under manipulation's fd still remains. It includes a model for extensibility, specifically to allow for future features around cgroup migration of sockets, and allowing for the fd to be taken (closing the fd in the process under manipulation). The syscall numbers were chosen to be one greater than openat2. Summary of history: This initially started as a ptrace command. It did not require the process to be stopped, and felt like kind of an awkward fit for ptrace. After that, it moved to an ioctl on the pidfd. Given functionality, it made sense to make it a syscall which did not require the process to be stopped. Changes since v4: * Turn into a syscall * Move to PTRACE_MODE_ATTACH_REALCREDS from PTRACE_MODE_READ_REALCREDS * Remove the sample code. This will come in another patchset, as the new self-tests cover all the functionality. Changes since v3: * Add self-test * Move to ioctl passing fd directly, versus args struct * Shuffle around include files Changes since v2: * Move to ioctl on pidfd instead of ptrace function * Add security check before moving file descriptor Changes since the RFC v1: * Introduce a new helper to fs/file.c to fetch a file descriptor from any process. It largely uses the code suggested by Oleg, with a few changes to fix locking * It uses an extensible options struct to supply the FD, and option. * I added a sample, using the code from the user-ptrace sample Sargun Dhillon (3): vfs, fdtable: Add get_task_file helper pid: Introduce pidfd_getfd syscall test: Add test for pidfd getfd MAINTAINERS | 1 + arch/alpha/kernel/syscalls/syscall.tbl | 1 + arch/arm/tools/syscall.tbl | 1 + arch/arm64/include/asm/unistd.h | 2 +- arch/arm64/include/asm/unistd32.h | 2 + arch/ia64/kernel/syscalls/syscall.tbl | 1 + arch/m68k/kernel/syscalls/syscall.tbl | 1 + arch/microblaze/kernel/syscalls/syscall.tbl | 1 + arch/mips/kernel/syscalls/syscall_n32.tbl | 1 + arch/mips/kernel/syscalls/syscall_n64.tbl | 1 + arch/mips/kernel/syscalls/syscall_o32.tbl | 1 + arch/parisc/kernel/syscalls/syscall.tbl | 1 + arch/powerpc/kernel/syscalls/syscall.tbl | 1 + arch/s390/kernel/syscalls/syscall.tbl | 1 + arch/sh/kernel/syscalls/syscall.tbl | 1 + arch/sparc/kernel/syscalls/syscall.tbl | 1 + arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + arch/xtensa/kernel/syscalls/syscall.tbl | 1 + fs/file.c | 22 +- include/linux/file.h | 2 + include/linux/syscalls.h | 4 + include/uapi/asm-generic/unistd.h | 3 +- include/uapi/linux/pidfd.h | 10 + kernel/pid.c | 115 ++++++++ tools/testing/selftests/pidfd/.gitignore | 1 + tools/testing/selftests/pidfd/Makefile | 2 +- .../selftests/pidfd/pidfd_getfd_test.c | 262 ++++++++++++++++++ 28 files changed, 437 insertions(+), 5 deletions(-) create mode 100644 include/uapi/linux/pidfd.h create mode 100644 tools/testing/selftests/pidfd/pidfd_getfd_test.c