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=-10.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 9A221C433E6 for ; Thu, 16 Jul 2020 12:49:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 714E520760 for ; Thu, 16 Jul 2020 12:49:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="YAQJZYTK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728479AbgGPMtK (ORCPT ); Thu, 16 Jul 2020 08:49:10 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:43087 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728477AbgGPMtJ (ORCPT ); Thu, 16 Jul 2020 08:49:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1594903746; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wQZLpoLtzsM5d9s2luOcVBYZTZ6mFy5zueA78VrJwvg=; b=YAQJZYTKQjuABY5qgxxDF3fGDnQhWsvSEMit84dyCRuIgI7y7kAQMJcJOAfZh3ocYF0uzR bN4zRTuNTwXSqRxGGM2OJkJIz3DrKdg4EaYdUHvfou2varbDTFF2hyPDL54ifR4GTXEiMF C4Dh0pvh8QB1S9ETCgqOQn7eBBQlw/0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-226-gXHKOYObP3aRqJwTt1_tlA-1; Thu, 16 Jul 2020 08:49:02 -0400 X-MC-Unique: gXHKOYObP3aRqJwTt1_tlA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 60FED100AA24; Thu, 16 Jul 2020 12:49:00 +0000 (UTC) Received: from steredhat.redhat.com (ovpn-114-107.ams2.redhat.com [10.36.114.107]) by smtp.corp.redhat.com (Postfix) with ESMTP id AC5D117D04; Thu, 16 Jul 2020 12:48:54 +0000 (UTC) From: Stefano Garzarella To: Jens Axboe Cc: Alexander Viro , Kernel Hardening , Kees Cook , Aleksa Sarai , Stefan Hajnoczi , Christian Brauner , Sargun Dhillon , Jann Horn , io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org, Jeff Moyer , linux-kernel@vger.kernel.org Subject: [PATCH RFC v2 2/3] io_uring: add IOURING_REGISTER_RESTRICTIONS opcode Date: Thu, 16 Jul 2020 14:48:32 +0200 Message-Id: <20200716124833.93667-3-sgarzare@redhat.com> In-Reply-To: <20200716124833.93667-1-sgarzare@redhat.com> References: <20200716124833.93667-1-sgarzare@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org The new io_uring_register(2) IOURING_REGISTER_RESTRICTIONS opcode permanently installs a feature allowlist on an io_ring_ctx. The io_ring_ctx can then be passed to untrusted code with the knowledge that only operations present in the allowlist can be executed. The allowlist approach ensures that new features added to io_uring do not accidentally become available when an existing application is launched on a newer kernel version. Currently is it possible to restrict sqe opcodes and register opcodes. It is also possible to allow only fixed files. IOURING_REGISTER_RESTRICTIONS can only be made once. Afterwards it is not possible to change restrictions anymore. This prevents untrusted code from removing restrictions. Suggested-by: Stefan Hajnoczi Signed-off-by: Stefano Garzarella --- RFC v2: - added 'restricted' flag in the ctx [Jens] - added IORING_MAX_RESTRICTIONS define - returned EBUSY instead of EINVAL when restrictions are already registered - reset restrictions if an error happened during the registration --- fs/io_uring.c | 102 +++++++++++++++++++++++++++++++++- include/uapi/linux/io_uring.h | 27 +++++++++ 2 files changed, 128 insertions(+), 1 deletion(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 9fd7e69696c3..23a2b03d9528 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -97,6 +97,8 @@ #define IORING_MAX_FILES_TABLE (1U << IORING_FILE_TABLE_SHIFT) #define IORING_FILE_TABLE_MASK (IORING_MAX_FILES_TABLE - 1) #define IORING_MAX_FIXED_FILES (64 * IORING_MAX_FILES_TABLE) +#define IORING_MAX_RESTRICTIONS (IORING_RESTRICTION_LAST + \ + IORING_REGISTER_LAST + IORING_OP_LAST) struct io_uring { u32 head ____cacheline_aligned_in_smp; @@ -218,6 +220,12 @@ struct io_buffer { __u16 bid; }; +struct io_restriction { + DECLARE_BITMAP(register_op, IORING_REGISTER_LAST); + DECLARE_BITMAP(sqe_op, IORING_OP_LAST); + DECLARE_BITMAP(restriction_op, IORING_RESTRICTION_LAST); +}; + struct io_ring_ctx { struct { struct percpu_ref refs; @@ -230,6 +238,7 @@ struct io_ring_ctx { unsigned int cq_overflow_flushed: 1; unsigned int drain_next: 1; unsigned int eventfd_async: 1; + unsigned int restricted: 1; /* * Ring buffer of indices into array of io_uring_sqe, which is @@ -337,6 +346,7 @@ struct io_ring_ctx { struct llist_head file_put_llist; struct work_struct exit_work; + struct io_restriction restrictions; }; /* @@ -5496,6 +5506,11 @@ static int io_req_set_file(struct io_submit_state *state, struct io_kiocb *req, if (unlikely(!fixed && io_async_submit(req->ctx))) return -EBADF; + if (unlikely(!fixed && req->ctx->restricted && + test_bit(IORING_RESTRICTION_FIXED_FILES_ONLY, + req->ctx->restrictions.restriction_op))) + return -EACCES; + return io_file_get(state, req, fd, &req->file, fixed); } @@ -5900,6 +5915,10 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req, if (unlikely(req->opcode >= IORING_OP_LAST)) return -EINVAL; + if (unlikely(ctx->restricted && + !test_bit(req->opcode, ctx->restrictions.sqe_op))) + return -EACCES; + if (unlikely(io_sq_thread_acquire_mm(ctx, req))) return -EFAULT; @@ -8099,6 +8118,71 @@ static int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id) return -EINVAL; } +static int io_register_restrictions(struct io_ring_ctx *ctx, void __user *arg, + unsigned int nr_args) +{ + struct io_uring_restriction *res; + size_t size; + int i, ret; + + /* We allow only a single restrictions registration */ + if (ctx->restricted) + return -EBUSY; + + if (!arg || nr_args > IORING_MAX_RESTRICTIONS) + return -EINVAL; + + size = array_size(nr_args, sizeof(*res)); + if (size == SIZE_MAX) + return -EOVERFLOW; + + res = kmalloc(size, GFP_KERNEL); + if (!res) + return -ENOMEM; + + if (copy_from_user(res, arg, size)) { + ret = -EFAULT; + goto out; + } + + for (i = 0; i < nr_args; i++) { + if (res[i].opcode >= IORING_RESTRICTION_LAST) { + ret = -EINVAL; + goto out; + } + + __set_bit(res[i].opcode, ctx->restrictions.restriction_op); + + if (res[i].opcode == IORING_RESTRICTION_REGISTER_OP) { + if (res[i].register_op >= IORING_REGISTER_LAST) { + ret = -EINVAL; + goto out; + } + + __set_bit(res[i].register_op, + ctx->restrictions.register_op); + } else if (res[i].opcode == IORING_RESTRICTION_SQE_OP) { + if (res[i].sqe_op >= IORING_OP_LAST) { + ret = -EINVAL; + goto out; + } + + __set_bit(res[i].sqe_op, ctx->restrictions.sqe_op); + } + } + + ctx->restricted = 1; + + ret = 0; +out: + /* Reset all restrictions if an error happened */ + if (ret != 0) + memset(&ctx->restrictions, 0, sizeof(ctx->restrictions)); + + kfree(res); + return ret; +} + static bool io_register_op_must_quiesce(int op) { switch (op) { @@ -8145,6 +8229,18 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode, if (ret) { percpu_ref_resurrect(&ctx->refs); ret = -EINTR; + goto out_quiesce; + } + } + + if (ctx->restricted) { + if (opcode >= IORING_REGISTER_LAST) { + ret = -EINVAL; + goto out; + } + + if (!test_bit(opcode, ctx->restrictions.register_op)) { + ret = -EACCES; goto out; } } @@ -8208,15 +8304,19 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode, break; ret = io_unregister_personality(ctx, nr_args); break; + case IORING_REGISTER_RESTRICTIONS: + ret = io_register_restrictions(ctx, arg, nr_args); + break; default: ret = -EINVAL; break; } +out: if (io_register_op_must_quiesce(opcode)) { /* bring the ctx back to life */ percpu_ref_reinit(&ctx->refs); -out: +out_quiesce: reinit_completion(&ctx->ref_comp); } return ret; diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index efc50bd0af34..0774d5382c65 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -265,6 +265,7 @@ enum { IORING_REGISTER_PROBE, IORING_REGISTER_PERSONALITY, IORING_UNREGISTER_PERSONALITY, + IORING_REGISTER_RESTRICTIONS, /* this goes last */ IORING_REGISTER_LAST @@ -293,4 +294,30 @@ struct io_uring_probe { struct io_uring_probe_op ops[0]; }; +struct io_uring_restriction { + __u16 opcode; + union { + __u8 register_op; /* IORING_RESTRICTION_REGISTER_OP */ + __u8 sqe_op; /* IORING_RESTRICTION_SQE_OP */ + }; + __u8 resv; + __u32 resv2[3]; +}; + +/* + * io_uring_restriction->opcode values + */ +enum { + /* Allow an io_uring_register(2) opcode */ + IORING_RESTRICTION_REGISTER_OP, + + /* Allow an sqe opcode */ + IORING_RESTRICTION_SQE_OP, + + /* Only allow fixed files */ + IORING_RESTRICTION_FIXED_FILES_ONLY, + + IORING_RESTRICTION_LAST +}; + #endif -- 2.26.2