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=-9.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,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 CE53CC169C4 for ; Tue, 29 Jan 2019 11:42:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 92CCF20882 for ; Tue, 29 Jan 2019 11:42:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548762133; bh=rO3gToCjTWaDo7iuaTpllq6rjVMza4ClfGhfukev2cA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=T1kJyqUfw+y5nE3gTh547JsCTly8hzNt6j1IzX9Nv79urmb/o91Yqt0eHt4r7pDn5 qcAo7y3vcPH0mXNk/bNdRdZkoaXDJH8ZC67dpGed7UC91+jN9W0wSn8osnJ7dblQOH CzmzYmckDqfI6ycHH3gIM5slfuwKbFTIDXUNk0xw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729992AbfA2LmM (ORCPT ); Tue, 29 Jan 2019 06:42:12 -0500 Received: from mail.kernel.org ([198.145.29.99]:59766 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729275AbfA2LmJ (ORCPT ); Tue, 29 Jan 2019 06:42:09 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.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 CC678214DA; Tue, 29 Jan 2019 11:42:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548762128; bh=rO3gToCjTWaDo7iuaTpllq6rjVMza4ClfGhfukev2cA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dMNJecOUNIS8lO0DSGXhLwfG8ISqrAbayNImpl4qVOICxtYPC+/NKMaBFJA/UKR5j VTuF69FWlnD609f/pvgzu9yUx1t0LPTAdfIfZAGg8S1EI8PT8ZDZEhqLbPmgTpomSN Xc1B4b2lcCw+nHazI3DbZEu9QWgjCvkSYWKmnrJo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Borkmann , Alexei Starovoitov , Sasha Levin Subject: [PATCH 4.20 100/117] bpf: restrict stack pointer arithmetic for unprivileged Date: Tue, 29 Jan 2019 12:35:51 +0100 Message-Id: <20190129113212.365725997@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190129113207.477505932@linuxfoundation.org> References: <20190129113207.477505932@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore 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 4.20-stable review patch. If anyone has any objections, please let me know. ------------------ [ commit e4298d25830a866cc0f427d4bccb858e76715859 upstream ] Restrict stack pointer arithmetic for unprivileged users in that arithmetic itself must not go out of bounds as opposed to the actual access later on. Therefore after each adjust_ptr_min_max_vals() with a stack pointer as a destination we simulate a check_stack_access() of 1 byte on the destination and once that fails the program is rejected for unprivileged program loads. This is analog to map value pointer arithmetic and needed for masking later on. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Signed-off-by: Sasha Levin --- kernel/bpf/verifier.c | 63 ++++++++++++++++++++++++++++--------------- 1 file changed, 41 insertions(+), 22 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 7c97d7cf4113..dc9c57f1a153 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1314,6 +1314,31 @@ static int check_stack_read(struct bpf_verifier_env *env, } } +static int check_stack_access(struct bpf_verifier_env *env, + const struct bpf_reg_state *reg, + int off, int size) +{ + /* Stack accesses must be at a fixed offset, so that we + * can determine what type of data were returned. See + * check_stack_read(). + */ + if (!tnum_is_const(reg->var_off)) { + char tn_buf[48]; + + tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); + verbose(env, "variable stack access var_off=%s off=%d size=%d", + tn_buf, off, size); + return -EACCES; + } + + if (off >= 0 || off < -MAX_BPF_STACK) { + verbose(env, "invalid stack off=%d size=%d\n", off, size); + return -EACCES; + } + + return 0; +} + /* check read/write into map element returned by bpf_map_lookup_elem() */ static int __check_map_access(struct bpf_verifier_env *env, u32 regno, int off, int size, bool zero_size_allowed) @@ -1870,24 +1895,10 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn } } else if (reg->type == PTR_TO_STACK) { - /* stack accesses must be at a fixed offset, so that we can - * determine what type of data were returned. - * See check_stack_read(). - */ - if (!tnum_is_const(reg->var_off)) { - char tn_buf[48]; - - tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); - verbose(env, "variable stack access var_off=%s off=%d size=%d", - tn_buf, off, size); - return -EACCES; - } off += reg->var_off.value; - if (off >= 0 || off < -MAX_BPF_STACK) { - verbose(env, "invalid stack off=%d size=%d\n", off, - size); - return -EACCES; - } + err = check_stack_access(env, reg, off, size); + if (err) + return err; state = func(env, reg); err = update_stack_depth(env, state, off); @@ -3169,11 +3180,19 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, /* For unprivileged we require that resulting offset must be in bounds * in order to be able to sanitize access later on. */ - if (!env->allow_ptr_leaks && dst_reg->type == PTR_TO_MAP_VALUE && - check_map_access(env, dst, dst_reg->off, 1, false)) { - verbose(env, "R%d pointer arithmetic of map value goes out of range, prohibited for !root\n", - dst); - return -EACCES; + if (!env->allow_ptr_leaks) { + if (dst_reg->type == PTR_TO_MAP_VALUE && + check_map_access(env, dst, dst_reg->off, 1, false)) { + verbose(env, "R%d pointer arithmetic of map value goes out of range, " + "prohibited for !root\n", dst); + return -EACCES; + } else if (dst_reg->type == PTR_TO_STACK && + check_stack_access(env, dst_reg, dst_reg->off + + dst_reg->var_off.value, 1)) { + verbose(env, "R%d stack pointer arithmetic goes out of range, " + "prohibited for !root\n", dst); + return -EACCES; + } } return 0; -- 2.19.1