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, URIBL_BLOCKED,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 541F9C43603 for ; Thu, 29 Apr 2021 22:08:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 397D961457 for ; Thu, 29 Apr 2021 22:08:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229721AbhD2WJa (ORCPT ); Thu, 29 Apr 2021 18:09:30 -0400 Received: from smtp-fw-4101.amazon.com ([72.21.198.25]:45052 "EHLO smtp-fw-4101.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229701AbhD2WJ3 (ORCPT ); Thu, 29 Apr 2021 18:09:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1619734123; x=1651270123; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=gmNWx/A3o7P+Kw8wXRNXjVF41jEqA3d1gWnTLKT66Qg=; b=K6NmR3vcG5MO7N38A2CrApFEd7Q+WjFEPx7mM8/V62nQcJUkjKxchOdp zih5RyDjSjFnFDOII1IvtJLdbY3awUrFAPj0159Zw31S40fSLiH2p5+pu xtvZuH0iBJDAWDiWPePu6SJKCdcrvCi/eLItzbWlimHRlVM0DSkW/0BVQ U=; X-IronPort-AV: E=Sophos;i="5.82,260,1613433600"; d="scan'208";a="104851474" Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-2a-53356bf6.us-west-2.amazon.com) ([10.43.8.6]) by smtp-border-fw-4101.iad4.amazon.com with ESMTP; 29 Apr 2021 22:08:41 +0000 Received: from EX13MTAUEB002.ant.amazon.com (pdx1-ws-svc-p6-lb9-vlan2.pdx.amazon.com [10.236.137.194]) by email-inbound-relay-2a-53356bf6.us-west-2.amazon.com (Postfix) with ESMTPS id A47A5A20FC; Thu, 29 Apr 2021 22:08:40 +0000 (UTC) Received: from EX13D20UEB003.ant.amazon.com (10.43.60.73) by EX13MTAUEB002.ant.amazon.com (10.43.60.12) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Thu, 29 Apr 2021 22:08:40 +0000 Received: from EX13MTAUEB002.ant.amazon.com (10.43.60.12) by EX13D20UEB003.ant.amazon.com (10.43.60.73) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Thu, 29 Apr 2021 22:08:40 +0000 Received: from dev-dsk-fllinden-2c-d7720709.us-west-2.amazon.com (172.19.206.175) by mail-relay.amazon.com (10.43.60.234) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Thu, 29 Apr 2021 22:08:39 +0000 Received: by dev-dsk-fllinden-2c-d7720709.us-west-2.amazon.com (Postfix, from userid 6262777) id D167AE6; Thu, 29 Apr 2021 22:08:39 +0000 (UTC) From: Frank van der Linden To: CC: Subject: [PATCH 5.4 4/8] bpf: Improve verifier error messages for users Date: Thu, 29 Apr 2021 22:08:35 +0000 Message-ID: <20210429220839.15667-5-fllinden@amazon.com> X-Mailer: git-send-email 2.23.4 In-Reply-To: <20210429220839.15667-1-fllinden@amazon.com> References: <20210429220839.15667-1-fllinden@amazon.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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 --- kernel/bpf/verifier.c | 84 +++++++++++++++++++++++++++++++------------ 1 file changed, 62 insertions(+), 22 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index a6ff4b26a462..59718101fd04 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4263,6 +4263,14 @@ static struct bpf_insn_aux_data *cur_aux(struct bpf_verifier_env *env) 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 struct bpf_reg_state *ptr_reg, 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 struct bpf_reg_state *ptr_reg, } 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(struct bpf_insn_aux_data *aux, 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 @@ static int sanitize_ptr_alu(struct bpf_verifier_env *env, 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(struct bpf_verifier_env *env, 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(struct bpf_verifier_env *env, 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(struct bpf_verifier_env *env, 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(struct bpf_verifier_env *env, 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(struct bpf_verifier_env *env, 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 */ -- 2.23.3