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[2620:137:e000::1:20]) by mx.google.com with ESMTP id x5-20020a654145000000b005579cc7bc7csi9503704pgp.246.2023.06.29.06.47.32; Thu, 29 Jun 2023 06:47:45 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20221208 header.b=JCTZZvCi; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231663AbjF2N1w (ORCPT + 99 others); Thu, 29 Jun 2023 09:27:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43596 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230353AbjF2N1s (ORCPT ); Thu, 29 Jun 2023 09:27:48 -0400 Received: from mail-ed1-x549.google.com (mail-ed1-x549.google.com [IPv6:2a00:1450:4864:20::549]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5B7E830EC for ; Thu, 29 Jun 2023 06:27:47 -0700 (PDT) Received: by mail-ed1-x549.google.com with SMTP id 4fb4d7f45d1cf-51dcfda6760so509252a12.0 for ; Thu, 29 Jun 2023 06:27:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1688045266; x=1690637266; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=kY7/aamj2EYJQ18ZqzDDw0qtsWDVxqm6PPibtWgkSrk=; b=JCTZZvCiBVSUwY/VlOx6zbqdMgQ8vDXSYLPyW51p0SzRVnKdolQReI6SJCJ5vCJQkI m6z3kLVUXRfoEy4ST9FRMGwRZ0LOUAsuQ3QUT2uZyIm+z20kRfnO0L/k2pEiKKfnhioe zlGZQQH5njPlya0jsgBopxygTxKMhnUaV/AxCKZdlfMEKO+IeFjrBuhi74rHneSf3IUx Rmu4B+vK7Ty0HmmhD4zU5q/ULFCW/yDPJIUGaztpIXYM35urnp5FMWLaYg9l9vu8jPkZ vwQVGrR+8gKRKvK4tywtkM1IsCxqrFmtJum9cyU+UAaiKCUirO9zfZfuSr04D6cXK4ke 00aA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1688045266; x=1690637266; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=kY7/aamj2EYJQ18ZqzDDw0qtsWDVxqm6PPibtWgkSrk=; b=RTjzlYtj0e81gzPWBGC3p6dUFTt2mGLj468JvOtj6wZI9T5sGgh0KfyoV4M/SvDITV yGanoyETDN4kLniXzVNIjwJ8I82zwSW4ubZWMjiuo2vuKk/w3R8RSpir+vlBKPz9g2wQ z783t6fgaYAKcEjEL0FMZhkPrTvDZP/CYG7ZWaRz643+D98ajxvnjIoaQZ8Pcw1AtlH5 U5rjzmXGQXYr8I2BdAlj8z42QZq8zQx50C6Z3B76cgsegFxcDU3JkImKJcaM+c1PMnuj tXzTa8eqi5IVgR7qhDk8l6187iZuPj0NrrOqc5S6AZNqZuvOYi4cm3sIMqSQsUI7OnUy vSFw== X-Gm-Message-State: AC+VfDw4LJM38nJVxswxGKCPxiJzF+zGjZsGru7PUxL6IEMFhH0EY/mW M7lccatrNd5FTcEDXw7NZv72lQaFlTXnn8wglA== X-Received: from mr-cloudtop2.c.googlers.com ([fda3:e722:ac3:cc00:31:98fb:c0a8:fb5]) (user=matteorizzo job=sendgmr) by 2002:a50:9f8e:0:b0:51b:df2d:60c5 with SMTP id c14-20020a509f8e000000b0051bdf2d60c5mr3202943edf.5.1688045265970; Thu, 29 Jun 2023 06:27:45 -0700 (PDT) Date: Thu, 29 Jun 2023 13:27:11 +0000 In-Reply-To: <20230629132711.1712536-1-matteorizzo@google.com> Mime-Version: 1.0 References: <20230629132711.1712536-1-matteorizzo@google.com> X-Mailer: git-send-email 2.41.0.162.gfafddb0af9-goog Message-ID: <20230629132711.1712536-2-matteorizzo@google.com> Subject: [PATCH v2 1/1] Add a new sysctl to disable io_uring system-wide From: Matteo Rizzo To: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, io-uring@vger.kernel.org Cc: matteorizzo@google.com, jordyzomer@google.com, evn@google.com, poprdi@google.com, corbet@lwn.net, axboe@kernel.dk, asml.silence@gmail.com, akpm@linux-foundation.org, keescook@chromium.org, rostedt@goodmis.org, dave.hansen@linux.intel.com, ribalda@chromium.org, chenhuacai@kernel.org, steve@sk2.org, gpiccoli@igalia.com, ldufour@linux.ibm.com, bhe@redhat.com, oleksandr@natalenko.name X-Spam-Status: No, score=-9.6 required=5.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1770045010371233673?= X-GMAIL-MSGID: =?utf-8?q?1770045010371233673?= Introduce a new sysctl (io_uring_disabled) which can be either 0, 1, or 2. When 0 (the default), all processes are allowed to create io_uring instances, which is the current behavior. When 1, all calls to io_uring_setup fail with -EPERM unless the calling process has CAP_SYS_ADMIN. When 2, calls to io_uring_setup fail with -EPERM regardless of privilege. Signed-off-by: Matteo Rizzo Reviewed-by: Jeff Moyer Reviewed-by: Gabriel Krisman Bertazi --- Documentation/admin-guide/sysctl/kernel.rst | 19 +++++++++++++ io_uring/io_uring.c | 30 +++++++++++++++++++++ 2 files changed, 49 insertions(+) diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index 3800fab1619b..ee65f7aeb0cf 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -450,6 +450,25 @@ this allows system administrators to override the ``IA64_THREAD_UAC_NOPRINT`` ``prctl`` and avoid logs being flooded. +io_uring_disabled +================= + +Prevents all processes from creating new io_uring instances. Enabling this +shrinks the kernel's attack surface. + += ================================================================== +0 All processes can create io_uring instances as normal. This is the + default setting. +1 io_uring creation is disabled for unprivileged processes. + io_uring_setup fails with -EPERM unless the calling process is + privileged (CAP_SYS_ADMIN). Existing io_uring instances can + still be used. +2 io_uring creation is disabled for all processes. io_uring_setup + always fails with -EPERM. Existing io_uring instances can still be + used. += ================================================================== + + kexec_load_disabled =================== diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 1b53a2ab0a27..2343ae518546 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -153,6 +153,22 @@ static __cold void io_fallback_tw(struct io_uring_task *tctx); struct kmem_cache *req_cachep; +static int __read_mostly sysctl_io_uring_disabled; +#ifdef CONFIG_SYSCTL +static struct ctl_table kernel_io_uring_disabled_table[] = { + { + .procname = "io_uring_disabled", + .data = &sysctl_io_uring_disabled, + .maxlen = sizeof(sysctl_io_uring_disabled), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_TWO, + }, + {}, +}; +#endif + struct sock *io_uring_get_socket(struct file *file) { #if defined(CONFIG_UNIX) @@ -4000,9 +4016,18 @@ static long io_uring_setup(u32 entries, struct io_uring_params __user *params) return io_uring_create(entries, &p, params); } +static inline bool io_uring_allowed(void) +{ + return sysctl_io_uring_disabled == 0 || + (sysctl_io_uring_disabled == 1 && capable(CAP_SYS_ADMIN)); +} + SYSCALL_DEFINE2(io_uring_setup, u32, entries, struct io_uring_params __user *, params) { + if (!io_uring_allowed()) + return -EPERM; + return io_uring_setup(entries, params); } @@ -4577,6 +4602,11 @@ static int __init io_uring_init(void) req_cachep = KMEM_CACHE(io_kiocb, SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT | SLAB_TYPESAFE_BY_RCU); + +#ifdef CONFIG_SYSCTL + register_sysctl_init("kernel", kernel_io_uring_disabled_table); +#endif + return 0; }; __initcall(io_uring_init);