From patchwork Wed Oct 16 03:44:30 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 1177560 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=ubuntu.com Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 46tJ8b0d2Zz9sPK for ; Wed, 16 Oct 2019 14:45:03 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732960AbfJPDot (ORCPT ); Tue, 15 Oct 2019 23:44:49 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:55614 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728940AbfJPDos (ORCPT ); Tue, 15 Oct 2019 23:44:48 -0400 Received: from [213.220.153.21] (helo=localhost.localdomain) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1iKaEw-0000Wg-Tw; Wed, 16 Oct 2019 03:44:46 +0000 From: Christian Brauner To: christian.brauner@ubuntu.com Cc: ast@kernel.org, bpf@vger.kernel.org, daniel@iogearbox.net, kafai@fb.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, songliubraving@fb.com, yhs@fb.com, Aleksa Sarai Subject: [PATCH v3 1/3] bpf: use check_zeroed_user() in bpf_check_uarg_tail_zero() Date: Wed, 16 Oct 2019 05:44:30 +0200 Message-Id: <20191016034432.4418-2-christian.brauner@ubuntu.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191016034432.4418-1-christian.brauner@ubuntu.com> References: <20191016004138.24845-1-christian.brauner@ubuntu.com> <20191016034432.4418-1-christian.brauner@ubuntu.com> MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org In v5.4-rc2 we added a new helper (cf. [1]) check_zeroed_user() which does what bpf_check_uarg_tail_zero() is doing generically. We're slowly switching such codepaths over to use check_zeroed_user() instead of using their own hand-rolled version. [1]: f5a1a536fa14 ("lib: introduce copy_struct_from_user() helper") Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: bpf@vger.kernel.org Acked-by: Aleksa Sarai Signed-off-by: Christian Brauner --- /* v1 */ Link: https://lore.kernel.org/r/20191009160907.10981-2-christian.brauner@ubuntu.com /* v2 */ Link: https://lore.kernel.org/r/20191016004138.24845-2-christian.brauner@ubuntu.com - Alexei Starovoitov : - Add a comment in bpf_check_uarg_tail_zero() to clarify that copy_struct_from_user() should be used whenever possible instead. /* v3 */ - Christian Brauner : - use correct checks for check_zeroed_user() --- kernel/bpf/syscall.c | 25 +++++++++---------------- 1 file changed, 9 insertions(+), 16 deletions(-) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 82eabd4e38ad..40edcaeccd71 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -58,35 +58,28 @@ static const struct bpf_map_ops * const bpf_map_types[] = { * There is a ToCToU between this function call and the following * copy_from_user() call. However, this is not a concern since this function is * meant to be a future-proofing of bits. + * + * Note, instead of using bpf_check_uarg_tail_zero() followed by + * copy_from_user() use the dedicated copy_struct_from_user() helper which + * performs both tasks whenever possible. */ int bpf_check_uarg_tail_zero(void __user *uaddr, size_t expected_size, size_t actual_size) { - unsigned char __user *addr; - unsigned char __user *end; - unsigned char val; + size_t size = min(expected_size, actual_size); + size_t rest = max(expected_size, actual_size) - size; int err; if (unlikely(actual_size > PAGE_SIZE)) /* silly large */ return -E2BIG; - if (unlikely(!access_ok(uaddr, actual_size))) - return -EFAULT; - if (actual_size <= expected_size) return 0; - addr = uaddr + expected_size; - end = uaddr + actual_size; - - for (; addr < end; addr++) { - err = get_user(val, addr); - if (err) - return err; - if (val) - return -E2BIG; - } + err = check_zeroed_user(uaddr + expected_size, rest); + if (err <= 0) + return err ?: -E2BIG; return 0; }