From patchwork Fri Jun 30 15:10:03 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matteo Rizzo X-Patchwork-Id: 13298316 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A328AEB64D7 for ; Fri, 30 Jun 2023 15:10:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232445AbjF3PK6 (ORCPT ); Fri, 30 Jun 2023 11:10:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232346AbjF3PK5 (ORCPT ); Fri, 30 Jun 2023 11:10:57 -0400 Received: from mail-ej1-x649.google.com (mail-ej1-x649.google.com [IPv6:2a00:1450:4864:20::649]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B44383A81 for ; Fri, 30 Jun 2023 08:10:55 -0700 (PDT) Received: by mail-ej1-x649.google.com with SMTP id a640c23a62f3a-94a34a0b75eso146777166b.1 for ; Fri, 30 Jun 2023 08:10:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1688137854; x=1690729854; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=t5yVCNzX7W1gRfvbajrTwlTVeQWrGAK4q/VSSd9dfqA=; b=wRD0T7EAigpqv2x6hJbLZj1kYlgIciGkbQCn3GQRJch3RlmIzNRilMGhZwheYiC8bO +5jxAhyIKtCTlfucML9q8/grI0N/T+DlgBnXMuM0NcfVktHdM16m2+1u3Pe9Ax3yM7P3 4PbJqpryGhBtO6kP7U7xsbUeQPvKMQP5kuGXOwj2MAQlJvFJyiLyyxuYhuktA/w5wbZk KNgj9dEM/RXv+qy9UQRmxtfzW/a0l7Cs/BlEBRRJY0iRB0w5MV/iaLxhCs3veCa8HE0h 8WpO1O9BN9n94/SFY1U5UXFvar5u3sTkWo1u3SJx+WRZ0v35+JwgSOlB7SsbcQxLoP3P ilDA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1688137854; x=1690729854; 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=t5yVCNzX7W1gRfvbajrTwlTVeQWrGAK4q/VSSd9dfqA=; b=Rz/XO8GD1JlOAy59ad4ady8DQ9b664cYzp955b4UgZlj1uQonTKNjEkZXUiuUU2ieY a7Wl2FeVcuOsWSZg3IE5I5MPBp4i2GbGCGJUIpsJz3k8SZeB3NM7NYSz4l0jp/cPOiP9 T9H++nVPsRtLLR4rDMPLQN5e+FVy3AbEyMuEfwT5MF940grVPuDQpXTiqudEprwj5Ad6 GLeuxvjxfKI8iRsrpuKPOTXdaxhpWxiAudVNuog1dBKI3nOvGP1YPof5Lpf0/EaVcbo+ beAVtwXS5AbcXxr8DypU5aNW1mBnWR/q34Y+viAkfNBkJTDvZSKxn1ZI9UFohSmaitKe NW3g== X-Gm-Message-State: ABy/qLbJnu25z6AbW3ZF5Stw1Zr6DOhA4tMxDPzdzYZFTseQzVGX99xi mq0/4jV6W85aPPiLx1YdzrQFv6uoBLMAvs/Oaw== X-Google-Smtp-Source: APBJJlHwSE7OK+c+fQ+eGFx7kZ+1YrrviqcQx9ITyGRJBG2Dk3t+Q6xw96scq3XLRhTRCFeLuZBnSWqRSlxC6xUbtg== X-Received: from mr-cloudtop2.c.googlers.com ([fda3:e722:ac3:cc00:31:98fb:c0a8:fb5]) (user=matteorizzo job=sendgmr) by 2002:a17:906:9159:b0:98f:bdb9:4a37 with SMTP id y25-20020a170906915900b0098fbdb94a37mr5326ejw.3.1688137854020; Fri, 30 Jun 2023 08:10:54 -0700 (PDT) Date: Fri, 30 Jun 2023 15:10:03 +0000 In-Reply-To: <20230630151003.3622786-1-matteorizzo@google.com> Mime-Version: 1.0 References: <20230630151003.3622786-1-matteorizzo@google.com> X-Mailer: git-send-email 2.41.0.255.g8b1d071c50-goog Message-ID: <20230630151003.3622786-2-matteorizzo@google.com> Subject: [PATCH v3 1/1] io_uring: add a 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, axboe@kernel.dk, asml.silence@gmail.com Cc: matteorizzo@google.com, corbet@lwn.net, akpm@linux-foundation.org, keescook@chromium.org, ribalda@chromium.org, rostedt@goodmis.org, jannh@google.com, chenhuacai@kernel.org, gpiccoli@igalia.com, ldufour@linux.ibm.com, evn@google.com, poprdi@google.com, jordyzomer@google.com, jmoyer@redhat.com, krisman@suse.de Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org 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 Reviewed-by: Jann Horn --- Documentation/admin-guide/sysctl/kernel.rst | 19 +++++++++++++ io_uring/io_uring.c | 31 +++++++++++++++++++++ 2 files changed, 50 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 e8096d502a7c..5410f5576980 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -152,6 +152,22 @@ static void __io_submit_flush_completions(struct io_ring_ctx *ctx); 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) @@ -4015,9 +4031,19 @@ 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) +{ + int disabled = READ_ONCE(sysctl_io_uring_disabled); + + return disabled == 0 || (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); } @@ -4592,6 +4618,11 @@ 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);