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=-6.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_GIT autolearn=ham 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 C6A83C10F14 for ; Thu, 18 Apr 2019 18:23:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9708920643 for ; Thu, 18 Apr 2019 18:23:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1555611828; bh=Pxzvkw2x6G81FdU2nkh3g/UYR8UlNTL3U0Y92xeVoII=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=HhQ1mXaQ5GabdwghX5kGmM1wJyb+eSgjJzQkJn6CKTBsrKSYIzmU6TZd2EhnChjw6 ouDXSRD8dKHekoMMdPBfgvOuIvD0oYiMfGB8wZ7nZxtda+SNd+a+5XRTsJyllBcnTP k1JXdIhH1VGJBLkUq8M9ikISBMChX/njRq3s1TFw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404113AbfDRSXr (ORCPT ); Thu, 18 Apr 2019 14:23:47 -0400 Received: from mail.kernel.org ([198.145.29.99]:36150 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391458AbfDRSGW (ORCPT ); Thu, 18 Apr 2019 14:06:22 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 40BE4218AF; Thu, 18 Apr 2019 18:06:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1555610781; bh=Pxzvkw2x6G81FdU2nkh3g/UYR8UlNTL3U0Y92xeVoII=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Q6ZrisV+s2+EiXwPUp9ok9TL9Uclq11D3r2ayNgOE3nM2PiCfnP5wiFnKSFdhkzz4 nUnI6fOd0ZUiCNgci2udv8lyd3JTT6YhKrPjPVrwp2pBpI7UKz2fRaN2FxGqzKiB2B MXfWRw9xNdBHXjsSppTeCP7oN/ux2pl13vtlM1iQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Borkmann , Alexei Starovoitov , Balbir Singh Subject: [PATCH 4.14 82/92] bpf: restrict unknown scalars of mixed signed bounds for unprivileged Date: Thu, 18 Apr 2019 19:57:40 +0200 Message-Id: <20190418160437.708923790@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190418160430.325165109@linuxfoundation.org> References: <20190418160430.325165109@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Daniel Borkmann commit 9d7eceede769f90b66cfa06ad5b357140d5141ed upstream. For unknown scalars of mixed signed bounds, meaning their smin_value is negative and their smax_value is positive, we need to reject arithmetic with pointer to map value. For unprivileged the goal is to mask every map pointer arithmetic and this cannot reliably be done when it is unknown at verification time whether the scalar value is negative or positive. Given this is a corner case, the likelihood of breaking should be very small. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: Alexei Starovoitov [backported to 4.14 sblbir] Signed-off-by: Balbir Singh Signed-off-by: Greg Kroah-Hartman --- kernel/bpf/verifier.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2014,8 +2014,8 @@ static int adjust_ptr_min_max_vals(struc smin_ptr = ptr_reg->smin_value, smax_ptr = ptr_reg->smax_value; u64 umin_val = off_reg->umin_value, umax_val = off_reg->umax_value, umin_ptr = ptr_reg->umin_value, umax_ptr = ptr_reg->umax_value; + u32 dst = insn->dst_reg, src = insn->src_reg; u8 opcode = BPF_OP(insn->code); - u32 dst = insn->dst_reg; dst_reg = ®s[dst]; @@ -2189,6 +2189,13 @@ static int adjust_ptr_min_max_vals(struc verbose("R%d bitwise operator %s on pointer prohibited\n", dst, bpf_alu_string[opcode >> 4]); return -EACCES; + case PTR_TO_MAP_VALUE: + if (!env->allow_ptr_leaks && !known && (smin_val < 0) != (smax_val < 0)) { + verbose("R%d has unknown scalar with mixed signed bounds, pointer arithmetic with it prohibited for !root\n", + off_reg == dst_reg ? dst : src); + return -EACCES; + } + /* fall-through */ default: /* other operators (e.g. MUL,LSH) produce non-pointer results */ if (!env->allow_ptr_leaks)