From patchwork Fri Jul 10 14:19:42 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefano Garzarella X-Patchwork-Id: 11656779 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 21E2413B4 for ; Fri, 10 Jul 2020 14:20:17 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 1B10B207D0 for ; Fri, 10 Jul 2020 14:20:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Vlpha8W+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1B10B207D0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-19278-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 9844 invoked by uid 550); 10 Jul 2020 14:20:14 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 9820 invoked from network); 10 Jul 2020 14:20:13 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1594390801; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=S/hfdY2jn078JPQClgP6PouoRBDjiWkYV+fASuPUqJA=; b=Vlpha8W+gfVSUDC8sJdYzNMYLSJbDGwtrnPJ1dIvei+SFgUNTxb/9rQJ7/2dDegtVprlf6 Cn9TVwZF+8TgvegnCilmVTSlqK9NxdGE/1QUt2EDDlSLbGeZRHvzpEeMvRAX+Xgib02tdR XO8q0aTjWi+KGitg8Bt04X1daD5hBjA= X-MC-Unique: Ur_35eYIO8ykayRn1yNGQw-1 From: Stefano Garzarella To: Jens Axboe Cc: Sargun Dhillon , Kees Cook , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Kernel Hardening , Jann Horn , Aleksa Sarai , Christian Brauner , Stefan Hajnoczi , io-uring@vger.kernel.org, Alexander Viro , Jeff Moyer Subject: [PATCH RFC 0/3] io_uring: add restrictions to support untrusted applications and guests Date: Fri, 10 Jul 2020 16:19:42 +0200 Message-Id: <20200710141945.129329-1-sgarzare@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Following the proposal that I send about restrictions [1], I wrote a PoC with the main changes. It is still WiP so I left some TODO in the code. I also wrote helpers in liburing and a test case (test/register-restrictions.c) available in this repository: https://github.com/stefano-garzarella/liburing (branch: io_uring_restrictions) Just to recap the proposal, the idea is to add some restrictions to the operations (sqe, register, fixed file) to safely allow untrusted applications or guests to use io_uring queues. The first patch changes io_uring_register(2) opcodes into an enumeration to keep track of the last opcode available. The second patch adds IOURING_REGISTER_RESTRICTIONS opcode and the code to handle restrictions. The third patch adds IORING_SETUP_R_DISABLED flag to start the rings disabled, allowing the user to register restrictions, buffers, files, before to start processing SQEs. I'm not sure if this could help seccomp. An alternative pointed out by Jann Horn could be to register restrictions during io_uring_setup(2), but this requires some intrusive changes (there is no space in the struct io_uring_params to pass a pointer to restriction arrays, maybe we can add a flag and add the pointer at the end of the struct io_uring_params). Another limitation now is that I need to enable every time IORING_REGISTER_ENABLE_RINGS in the restrictions to be able to start the rings, I'm not sure if we should treat it as an exception. Maybe registering restrictions during io_uring_setup(2) could solve both issues (seccomp integration and IORING_REGISTER_ENABLE_RINGS registration), but I need some suggestions to properly extend the io_uring_setup(2). Comments and suggestions are very welcome. Thank you in advance, Stefano [1] https://lore.kernel.org/io-uring/20200609142406.upuwpfmgqjeji4lc@steredhat/ Stefano Garzarella (3): io_uring: use an enumeration for io_uring_register(2) opcodes io_uring: add IOURING_REGISTER_RESTRICTIONS opcode io_uring: allow disabling rings during the creation fs/io_uring.c | 155 ++++++++++++++++++++++++++++++++-- include/uapi/linux/io_uring.h | 59 ++++++++++--- 2 files changed, 194 insertions(+), 20 deletions(-)