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=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 3D7A8C4160E for ; Fri, 19 Mar 2021 12:21:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0D30564F7E for ; Fri, 19 Mar 2021 12:21:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231249AbhCSMU7 (ORCPT ); Fri, 19 Mar 2021 08:20:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:58422 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230481AbhCSMU0 (ORCPT ); Fri, 19 Mar 2021 08:20:26 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5AB8664FA1; Fri, 19 Mar 2021 12:20:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1616156414; bh=iNLNdrtmsO6DnAhgiLpQNILkfvso9NVdSQ4vT0zKqQ4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oNSX46Jxys4in4WRVBT0zW+napGdU4eaEcqEquhu/j3Gk9tgrQLUpWkIYlDNs0Jnk Mgrtle8OufmhkNznYEapewWD+9RYi0dyP5EwIR1glFgyUZkl1wLO7cU5xpayqjGRVy mI1ZnX5/DwWgaxz9Eb10LJ8rkovW5k1RjZ4yqInA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Piotr Krysiuk , Daniel Borkmann , Alexei Starovoitov Subject: [PATCH 5.10 06/13] bpf: Add sanity check for upper ptr_limit Date: Fri, 19 Mar 2021 13:19:03 +0100 Message-Id: <20210319121745.310254598@linuxfoundation.org> X-Mailer: git-send-email 2.31.0 In-Reply-To: <20210319121745.112612545@linuxfoundation.org> References: <20210319121745.112612545@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Piotr Krysiuk commit 1b1597e64e1a610c7a96710fc4717158e98a08b3 upstream. Given we know the max possible value of ptr_limit at the time of retrieving the latter, add basic assertions, so that the verifier can bail out if anything looks odd and reject the program. Nothing triggered this so far, but it also does not hurt to have these. Signed-off-by: Piotr Krysiuk Co-developed-by: Daniel Borkmann Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: Greg Kroah-Hartman --- kernel/bpf/verifier.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5333,10 +5333,14 @@ static int retrieve_ptr_limit(const stru { bool mask_to_left = (opcode == BPF_ADD && off_is_neg) || (opcode == BPF_SUB && !off_is_neg); - u32 off; + u32 off, max; switch (ptr_reg->type) { case PTR_TO_STACK: + /* Offset 0 is out-of-bounds, but acceptable start for the + * left direction, see BPF_REG_FP. + */ + max = MAX_BPF_STACK + mask_to_left; /* Indirect variable offset stack access is prohibited in * unprivileged mode so it's not handled here. */ @@ -5345,15 +5349,16 @@ static int retrieve_ptr_limit(const stru *ptr_limit = MAX_BPF_STACK + off; else *ptr_limit = -off - 1; - return 0; + return *ptr_limit >= max ? -ERANGE : 0; case PTR_TO_MAP_VALUE: + max = ptr_reg->map_ptr->value_size; if (mask_to_left) { *ptr_limit = ptr_reg->umax_value + ptr_reg->off; } else { off = ptr_reg->smin_value + ptr_reg->off; *ptr_limit = ptr_reg->map_ptr->value_size - off - 1; } - return 0; + return *ptr_limit >= max ? -ERANGE : 0; default: return -EINVAL; }