From patchwork Fri Apr 30 14:20:18 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 12233517 X-Patchwork-Delegate: bpf@iogearbox.net 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 27555C4360C for ; Fri, 30 Apr 2021 14:20:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 11F246146D for ; Fri, 30 Apr 2021 14:20:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232838AbhD3OV2 (ORCPT ); Fri, 30 Apr 2021 10:21:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:57584 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232733AbhD3OV1 (ORCPT ); Fri, 30 Apr 2021 10:21:27 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 68EB3613EA; Fri, 30 Apr 2021 14:20:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1619792437; bh=GJ5X9/H08GNtaamz9yw9lSw5QNFnvKuTgtA+ddDYL1w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=r/893XdqlP+P+Qc2kyyLin++6vm2VGVDbujHhBIoGROlkW9mFHqXB2qBqpfTbc6rz yjSnSjJPZyJZKgtsEIrvZ5AqMWy5WJa5Pmg90FN21mibZ1ZX3oiOddwicMHQiHk/Iq x9mfzPXMKJp2MW2Nrq3TcO/ux21ZV/izCefLoIiI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , bpf@vger.kernel.org, Daniel Borkmann , John Fastabend , Alexei Starovoitov , Frank van der Linden Subject: [PATCH 5.4 4/8] bpf: Improve verifier error messages for users Date: Fri, 30 Apr 2021 16:20:18 +0200 Message-Id: <20210430141911.295796543@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210430141911.137473863@linuxfoundation.org> References: <20210430141911.137473863@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net From: Daniel Borkmann commit a6aaece00a57fa6f22575364b3903dfbccf5345d upstream. Consolidate all error handling and provide more user-friendly error messages from sanitize_ptr_alu() and sanitize_val_alu(). Signed-off-by: Daniel Borkmann Reviewed-by: John Fastabend Acked-by: Alexei Starovoitov [fllinden@amazon.com: backport to 5.4] Signed-off-by: Frank van der Linden Signed-off-by: Greg Kroah-Hartman --- kernel/bpf/verifier.c | 84 ++++++++++++++++++++++++++++++++++++-------------- 1 file changed, 62 insertions(+), 22 deletions(-) --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4263,6 +4263,14 @@ static struct bpf_insn_aux_data *cur_aux return &env->insn_aux_data[env->insn_idx]; } +enum { + REASON_BOUNDS = -1, + REASON_TYPE = -2, + REASON_PATHS = -3, + REASON_LIMIT = -4, + REASON_STACK = -5, +}; + static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg, const struct bpf_reg_state *off_reg, u32 *alu_limit, u8 opcode) @@ -4274,7 +4282,7 @@ static int retrieve_ptr_limit(const stru if (!tnum_is_const(off_reg->var_off) && (off_reg->smin_value < 0) != (off_reg->smax_value < 0)) - return -EACCES; + return REASON_BOUNDS; switch (ptr_reg->type) { case PTR_TO_STACK: @@ -4301,11 +4309,11 @@ static int retrieve_ptr_limit(const stru } break; default: - return -EINVAL; + return REASON_TYPE; } if (ptr_limit >= max) - return -ERANGE; + return REASON_LIMIT; *alu_limit = ptr_limit; return 0; } @@ -4325,7 +4333,7 @@ static int update_alu_sanitation_state(s if (aux->alu_state && (aux->alu_state != alu_state || aux->alu_limit != alu_limit)) - return -EACCES; + return REASON_PATHS; /* Corresponding fixup done in fixup_bpf_calls(). */ aux->alu_state = alu_state; @@ -4398,7 +4406,46 @@ do_sim: ret = push_stack(env, env->insn_idx + 1, env->insn_idx, true); if (!ptr_is_dst_reg && ret) *dst_reg = tmp; - return !ret ? -EFAULT : 0; + return !ret ? REASON_STACK : 0; +} + +static int sanitize_err(struct bpf_verifier_env *env, + const struct bpf_insn *insn, int reason, + const struct bpf_reg_state *off_reg, + const struct bpf_reg_state *dst_reg) +{ + static const char *err = "pointer arithmetic with it prohibited for !root"; + const char *op = BPF_OP(insn->code) == BPF_ADD ? "add" : "sub"; + u32 dst = insn->dst_reg, src = insn->src_reg; + + switch (reason) { + case REASON_BOUNDS: + verbose(env, "R%d has unknown scalar with mixed signed bounds, %s\n", + off_reg == dst_reg ? dst : src, err); + break; + case REASON_TYPE: + verbose(env, "R%d has pointer with unsupported alu operation, %s\n", + off_reg == dst_reg ? src : dst, err); + break; + case REASON_PATHS: + verbose(env, "R%d tried to %s from different maps, paths or scalars, %s\n", + dst, op, err); + break; + case REASON_LIMIT: + verbose(env, "R%d tried to %s beyond pointer bounds, %s\n", + dst, op, err); + break; + case REASON_STACK: + verbose(env, "R%d could not be pushed for speculative verification, %s\n", + dst, err); + break; + default: + verbose(env, "verifier internal error: unknown reason (%d)\n", + reason); + break; + } + + return -EACCES; } /* Handles arithmetic on a pointer and a scalar: computes new min/max and var_off. @@ -4480,10 +4527,9 @@ static int adjust_ptr_min_max_vals(struc switch (opcode) { case BPF_ADD: ret = sanitize_ptr_alu(env, insn, ptr_reg, off_reg, dst_reg); - if (ret < 0) { - verbose(env, "R%d tried to add from different maps, paths, or prohibited types\n", dst); - return ret; - } + if (ret < 0) + return sanitize_err(env, insn, ret, off_reg, dst_reg); + /* We can take a fixed offset as long as it doesn't overflow * the s32 'off' field */ @@ -4535,10 +4581,9 @@ static int adjust_ptr_min_max_vals(struc break; case BPF_SUB: ret = sanitize_ptr_alu(env, insn, ptr_reg, off_reg, dst_reg); - if (ret < 0) { - verbose(env, "R%d tried to sub from different maps, paths, or prohibited types\n", dst); - return ret; - } + if (ret < 0) + return sanitize_err(env, insn, ret, off_reg, dst_reg); + if (dst_reg == off_reg) { /* scalar -= pointer. Creates an unknown scalar */ verbose(env, "R%d tried to subtract pointer from scalar\n", @@ -4655,7 +4700,6 @@ static int adjust_scalar_min_max_vals(st s64 smin_val, smax_val; u64 umin_val, umax_val; u64 insn_bitness = (BPF_CLASS(insn->code) == BPF_ALU64) ? 64 : 32; - u32 dst = insn->dst_reg; int ret; if (insn_bitness == 32) { @@ -4692,10 +4736,8 @@ static int adjust_scalar_min_max_vals(st switch (opcode) { case BPF_ADD: ret = sanitize_val_alu(env, insn); - if (ret < 0) { - verbose(env, "R%d tried to add from different pointers or scalars\n", dst); - return ret; - } + if (ret < 0) + return sanitize_err(env, insn, ret, NULL, NULL); if (signed_add_overflows(dst_reg->smin_value, smin_val) || signed_add_overflows(dst_reg->smax_value, smax_val)) { dst_reg->smin_value = S64_MIN; @@ -4716,10 +4758,8 @@ static int adjust_scalar_min_max_vals(st break; case BPF_SUB: ret = sanitize_val_alu(env, insn); - if (ret < 0) { - verbose(env, "R%d tried to sub from different pointers or scalars\n", dst); - return ret; - } + if (ret < 0) + return sanitize_err(env, insn, ret, NULL, NULL); if (signed_sub_overflows(dst_reg->smin_value, smax_val) || signed_sub_overflows(dst_reg->smax_value, smin_val)) { /* Overflow possible, we know nothing */