From patchwork Tue Jun 28 16:19:45 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: KP Singh X-Patchwork-Id: 12898530 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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 875F7CCA488 for ; Tue, 28 Jun 2022 16:30:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233843AbiF1QaR (ORCPT ); Tue, 28 Jun 2022 12:30:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48028 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347545AbiF1Q3K (ORCPT ); Tue, 28 Jun 2022 12:29:10 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 63C773A189; Tue, 28 Jun 2022 09:20:00 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 21BC1B81EA4; Tue, 28 Jun 2022 16:19:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 32244C341C8; Tue, 28 Jun 2022 16:19:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1656433197; bh=AcNuOCR5+c8FlyRF2gJBdkVGbfQprs6DCiPiX5v7zyE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=I1+HS8ck/uWSgFRzYFxgi/pCmJ8Iw4cyxDroJADV6VlP5A1GC0zuoW9E3JCRW9zOe YfUX9tOYkXu8Y/c40yHp0GgxkysGir9KPhFBAEAb3mY80pZQBxrJaC1Ut/Vv4ebAzk qzOPnfBiJM6z3ZnhDqBa5oBG1pHlthZe3jSJ8zI38mxjocxYwBisBtJVpUhhLdNmzQ w0TKQcZsnjV14Z0sRPT2G3KCd/aYPwQJZco9Smp4JYxOSP0NKvIii09UPveB3X3xhw irzm32K0ZU4rcJSBOk1amAl0I10t5k4i9DOZ3GNDqenV6F52mQNPCTMzf2HZL4fZHV WCzVR/a6CkALw== From: KP Singh To: bpf@vger.kernel.org, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: KP Singh , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Benjamin Tissoires , Yosry Ahmed Subject: [PATCH v5 bpf-next 2/5] bpf: kfunc support for ARG_PTR_TO_CONST_STR Date: Tue, 28 Jun 2022 16:19:45 +0000 Message-Id: <20220628161948.475097-3-kpsingh@kernel.org> X-Mailer: git-send-email 2.37.0.rc0.161.g10f37bed90-goog In-Reply-To: <20220628161948.475097-1-kpsingh@kernel.org> References: <20220628161948.475097-1-kpsingh@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net kfuncs can handle pointers to memory when the next argument is the size of the memory that can be read and verify these as ARG_CONST_SIZE_OR_ZERO Similarly add support for string constants (const char *) and verify it similar to ARG_PTR_TO_CONST_STR. Signed-off-by: KP Singh --- include/linux/bpf_verifier.h | 2 + kernel/bpf/btf.c | 30 ++++++++++++ kernel/bpf/verifier.c | 89 +++++++++++++++++++++--------------- 3 files changed, 83 insertions(+), 38 deletions(-) diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 81b19669efba..f6d8898270d5 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -560,6 +560,8 @@ int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state u32 regno); int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg, u32 regno, u32 mem_size); +int check_const_str(struct bpf_verifier_env *env, + const struct bpf_reg_state *reg, int regno); /* this lives here instead of in bpf.h because it needs to dereference tgt_prog */ static inline u64 bpf_trampoline_compute_key(const struct bpf_prog *tgt_prog, diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 37bc77b3b499..9b9d6117deae 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6162,6 +6162,27 @@ static bool is_kfunc_arg_mem_size(const struct btf *btf, return true; } +static bool btf_param_is_const_str_ptr(const struct btf *btf, + const struct btf_param *param) +{ + const struct btf_type *t; + bool is_const = false; + + t = btf_type_by_id(btf, param->type); + if (!btf_type_is_ptr(t)) + return false; + + t = btf_type_by_id(btf, t->type); + while (btf_type_is_modifier(t)) { + if (BTF_INFO_KIND(t->info) == BTF_KIND_CONST) + is_const = true; + t = btf_type_by_id(btf, t->type); + } + + return (is_const && + !strcmp(btf_name_by_offset(btf, t->name_off), "char")); +} + static int btf_check_func_arg_match(struct bpf_verifier_env *env, const struct btf *btf, u32 func_id, struct bpf_reg_state *regs, @@ -6344,10 +6365,19 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, } else if (ptr_to_mem_ok) { const struct btf_type *resolve_ret; u32 type_size; + int err; if (is_kfunc) { bool arg_mem_size = i + 1 < nargs && is_kfunc_arg_mem_size(btf, &args[i + 1], ®s[regno + 1]); + + if (btf_param_is_const_str_ptr(btf, &args[i])) { + err = check_const_str(env, reg, regno); + if (err < 0) + return err; + continue; + } + /* Permit pointer to mem, but only when argument * type is pointer to scalar, or struct composed * (recursively) of scalars. diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 4938477912cd..8ce5d2f86c1e 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5840,6 +5840,56 @@ static u32 stack_slot_get_id(struct bpf_verifier_env *env, struct bpf_reg_state return state->stack[spi].spilled_ptr.id; } +int check_const_str(struct bpf_verifier_env *env, + const struct bpf_reg_state *reg, int regno) +{ + struct bpf_map *map; + int map_off; + u64 map_addr; + char *str_ptr; + int err; + + if (reg->type != PTR_TO_MAP_VALUE) + return -EACCES; + + map = reg->map_ptr; + if (!bpf_map_is_rdonly(map)) { + verbose(env, "R%d does not point to a readonly map'\n", regno); + return -EACCES; + } + + if (!tnum_is_const(reg->var_off)) { + verbose(env, "R%d is not a constant address'\n", regno); + return -EACCES; + } + + if (!map->ops->map_direct_value_addr) { + verbose(env, + "no direct value access support for this map type\n"); + return -EACCES; + } + + err = check_map_access(env, regno, reg->off, map->value_size - reg->off, + false, ACCESS_HELPER); + if (err) + return err; + + map_off = reg->off + reg->var_off.value; + err = map->ops->map_direct_value_addr(map, &map_addr, map_off); + if (err) { + verbose(env, "direct value access on string failed\n"); + return err; + } + + str_ptr = (char *)(long)(map_addr); + if (!strnchr(str_ptr + map_off, map->value_size - map_off, 0)) { + verbose(env, "string is not zero-terminated\n"); + return -EINVAL; + } + + return 0; +} + static int check_func_arg(struct bpf_verifier_env *env, u32 arg, struct bpf_call_arg_meta *meta, const struct bpf_func_proto *fn) @@ -6074,44 +6124,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, return err; err = check_ptr_alignment(env, reg, 0, size, true); } else if (arg_type == ARG_PTR_TO_CONST_STR) { - struct bpf_map *map = reg->map_ptr; - int map_off; - u64 map_addr; - char *str_ptr; - - if (!bpf_map_is_rdonly(map)) { - verbose(env, "R%d does not point to a readonly map'\n", regno); - return -EACCES; - } - - if (!tnum_is_const(reg->var_off)) { - verbose(env, "R%d is not a constant address'\n", regno); - return -EACCES; - } - - if (!map->ops->map_direct_value_addr) { - verbose(env, "no direct value access support for this map type\n"); - return -EACCES; - } - - err = check_map_access(env, regno, reg->off, - map->value_size - reg->off, false, - ACCESS_HELPER); - if (err) - return err; - - map_off = reg->off + reg->var_off.value; - err = map->ops->map_direct_value_addr(map, &map_addr, map_off); - if (err) { - verbose(env, "direct value access on string failed\n"); - return err; - } - - str_ptr = (char *)(long)(map_addr); - if (!strnchr(str_ptr + map_off, map->value_size - map_off, 0)) { - verbose(env, "string is not zero-terminated\n"); - return -EINVAL; - } + err = check_const_str(env, reg, regno); } else if (arg_type == ARG_PTR_TO_KPTR) { if (process_kptr_func(env, regno, meta)) return -EACCES;