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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 9242DC54E8E for ; Tue, 12 May 2020 15:05:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 75C3D206F5 for ; Tue, 12 May 2020 15:05:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730898AbgELPF3 (ORCPT ); Tue, 12 May 2020 11:05:29 -0400 Received: from www62.your-server.de ([213.133.104.62]:60050 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730763AbgELPFQ (ORCPT ); Tue, 12 May 2020 11:05:16 -0400 Received: from sslproxy01.your-server.de ([78.46.139.224]) by www62.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1jYWT3-0001eq-DD; Tue, 12 May 2020 17:05:13 +0200 Received: from [2001:1620:665:0:5795:5b0a:e5d5:5944] (helo=linux-5.fritz.box) by sslproxy01.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1jYWT3-000X97-1y; Tue, 12 May 2020 17:05:13 +0200 Subject: Re: [PATCH v5 bpf-next 2/3] bpf: implement CAP_BPF To: Alexei Starovoitov , davem@davemloft.net Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com, linux-security-module@vger.kernel.org, acme@redhat.com, jamorris@linux.microsoft.com, jannh@google.com, kpsingh@google.com References: <20200508215340.41921-1-alexei.starovoitov@gmail.com> <20200508215340.41921-3-alexei.starovoitov@gmail.com> From: Daniel Borkmann Message-ID: Date: Tue, 12 May 2020 17:05:12 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20200508215340.41921-3-alexei.starovoitov@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.102.2/25810/Tue May 12 14:14:24 2020) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 5/8/20 11:53 PM, Alexei Starovoitov wrote: > From: Alexei Starovoitov > > Implement permissions as stated in uapi/linux/capability.h > In order to do that the verifier allow_ptr_leaks flag is split > into allow_ptr_leaks and bpf_capable flags and they are set as: > env->allow_ptr_leaks = perfmon_capable(); > env->bpf_capable = bpf_capable(); [...] > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 70ad009577f8..a6893746cd87 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -1293,7 +1293,7 @@ static void __mark_reg_unknown(const struct bpf_verifier_env *env, > reg->type = SCALAR_VALUE; > reg->var_off = tnum_unknown; > reg->frameno = 0; > - reg->precise = env->subprog_cnt > 1 || !env->allow_ptr_leaks; > + reg->precise = env->subprog_cnt > 1 || !env->bpf_capable; > __mark_reg_unbounded(reg); > } > > @@ -1425,8 +1425,9 @@ static int check_subprogs(struct bpf_verifier_env *env) > continue; > if (insn[i].src_reg != BPF_PSEUDO_CALL) > continue; > - if (!env->allow_ptr_leaks) { > - verbose(env, "function calls to other bpf functions are allowed for root only\n"); > + if (!env->bpf_capable) { > + verbose(env, > + "function calls to other bpf functions are allowed for CAP_BPF and CAP_SYS_ADMIN\n"); > return -EPERM; > } > ret = add_subprog(env, i + insn[i].imm + 1); > @@ -1960,7 +1961,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno, > bool new_marks = false; > int i, err; > > - if (!env->allow_ptr_leaks) > + if (!env->bpf_capable) > /* backtracking is root only for now */ > return 0; > > @@ -2208,7 +2209,7 @@ static int check_stack_write(struct bpf_verifier_env *env, > reg = &cur->regs[value_regno]; > > if (reg && size == BPF_REG_SIZE && register_is_const(reg) && > - !register_is_null(reg) && env->allow_ptr_leaks) { > + !register_is_null(reg) && env->bpf_capable) { > if (dst_reg != BPF_REG_FP) { > /* The backtracking logic can only recognize explicit > * stack slot address like [fp - 8]. Other spill of > @@ -3428,7 +3429,7 @@ static int check_stack_boundary(struct bpf_verifier_env *env, int regno, > * Spectre masking for stack ALU. > * See also retrieve_ptr_limit(). > */ > - if (!env->allow_ptr_leaks) { > + if (!env->bpf_capable) { > char tn_buf[48]; > > tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); > @@ -7229,7 +7230,7 @@ static int push_insn(int t, int w, int e, struct bpf_verifier_env *env, > insn_stack[env->cfg.cur_stack++] = w; > return 1; > } else if ((insn_state[w] & 0xF0) == DISCOVERED) { > - if (loop_ok && env->allow_ptr_leaks) > + if (loop_ok && env->bpf_capable) > return 0; > verbose_linfo(env, t, "%d: ", t); > verbose_linfo(env, w, "%d: ", w); > @@ -8338,7 +8339,7 @@ static int is_state_visited(struct bpf_verifier_env *env, int insn_idx) > if (env->max_states_per_insn < states_cnt) > env->max_states_per_insn = states_cnt; > > - if (!env->allow_ptr_leaks && states_cnt > BPF_COMPLEXITY_LIMIT_STATES) > + if (!env->bpf_capable && states_cnt > BPF_COMPLEXITY_LIMIT_STATES) > return push_jmp_history(env, cur); > > if (!add_new_state) > @@ -9998,7 +9999,7 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env) > insn->code = BPF_JMP | BPF_TAIL_CALL; > > aux = &env->insn_aux_data[i + delta]; > - if (env->allow_ptr_leaks && !expect_blinding && > + if (env->bpf_capable && !expect_blinding && > prog->jit_requested && > !bpf_map_key_poisoned(aux) && > !bpf_map_ptr_poisoned(aux) && > @@ -10725,7 +10726,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, > env->insn_aux_data[i].orig_idx = i; > env->prog = *prog; > env->ops = bpf_verifier_ops[env->prog->type]; > - is_priv = capable(CAP_SYS_ADMIN); > + is_priv = bpf_capable(); > > if (!btf_vmlinux && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) { > mutex_lock(&bpf_verifier_lock); > @@ -10766,7 +10767,8 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, > if (attr->prog_flags & BPF_F_ANY_ALIGNMENT) > env->strict_alignment = false; > > - env->allow_ptr_leaks = is_priv; > + env->allow_ptr_leaks = perfmon_capable(); > + env->bpf_capable = bpf_capable(); Probably more of a detail, but it feels weird to tie perfmon_capable() into the BPF core and use it in various places there. I would rather make this a proper bpf_* prefixed helper and add a more descriptive name (what does it have to do with perf or monitoring directly?). For example, all the main functionality could be under `bpf_base_capable()` and everything with potential to leak pointers or mem to user space as `bpf_leak_capable()`. Then inside include/linux/capability.h this can still resolve under the hood to something like: static inline bool bpf_base_capable(void) { return capable(CAP_BPF) || capable(CAP_SYS_ADMIN); } static inline bool bpf_leak_capable(void) { return perfmon_capable(); } Thanks, Daniel