From patchwork Mon Apr 12 15:37:50 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florent Revest X-Patchwork-Id: 12198387 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=-18.8 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=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 ADD8BC433B4 for ; Mon, 12 Apr 2021 15:38:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8CFEF61249 for ; Mon, 12 Apr 2021 15:38:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243143AbhDLPiZ (ORCPT ); Mon, 12 Apr 2021 11:38:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41814 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243128AbhDLPiV (ORCPT ); Mon, 12 Apr 2021 11:38:21 -0400 Received: from mail-wr1-x42a.google.com (mail-wr1-x42a.google.com [IPv6:2a00:1450:4864:20::42a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42526C061342 for ; Mon, 12 Apr 2021 08:38:03 -0700 (PDT) Received: by mail-wr1-x42a.google.com with SMTP id a4so13428672wrr.2 for ; Mon, 12 Apr 2021 08:38:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=+1UwroWLTYhoseLYHrN5fe9n/sHopx/KmRUhVO1MbI4=; b=RuJXRSxR+Ov40JlDqtoUZMAmCM21PuHuu1WkkIEyaNBRrFQEHICJ2o3tt9RT6N/ZNF +eYdN5qJRI65HRCL49DOJQIwcRg/53YxcRQ7L4AplBce+WD5u8J1Oku4LQgRgwp9Lpee T+nOPUWqVkzhbovOUfiydClrg1/yQcIBwo+qM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=+1UwroWLTYhoseLYHrN5fe9n/sHopx/KmRUhVO1MbI4=; b=KfVr6xEcdvho03jatfvVbqdGgYIfOgkUlcTYmcswkKqJQT3KJyve/0tfTIL6SDY9Vw DextZwCoJEhtWP29aKq0+d1luMpH5CVCdrv+dN/CE0V9Vs83HoLuA/Yt26qKNFKq34Jf +U96DK/AIVtrLBuEyertxvadXwBemgjhTBdel1qEGJYMMc4vRoX+UZh7rBT57HynGRwE OuPTmwskRL9tYiTv7z8HL5qwhY3tzC8yjst9DxMyqqyVTDa9a3uwNz30RGDI63Xkkmt6 3Cm7FWML59ExQg7/M/enShAwA8pHqNj0Ex40RA/mRNh1FpaDQYQ7+ckZoqvc65co1Zr6 +isw== X-Gm-Message-State: AOAM533yV/IX5rT5pFVkZUNOXUPZCUYqAPiz1raFtkWgkzBs9rb4rRZW On6Yeq7yCPJHhCejUG/tnVG3dKK/aQnFlw== X-Google-Smtp-Source: ABdhPJxO/rK9c1OYmk4OH9lPBTCnQvWHbnbshhhVC6rgen0xIkACHbIXQWXezMUou2gMdSKcy5XGeQ== X-Received: by 2002:adf:dd51:: with SMTP id u17mr6753523wrm.32.1618241881711; Mon, 12 Apr 2021 08:38:01 -0700 (PDT) Received: from revest.zrh.corp.google.com ([2a00:79e0:42:204:a372:3c3b:eeb:ad14]) by smtp.gmail.com with ESMTPSA id i4sm2501449wrx.56.2021.04.12.08.38.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Apr 2021 08:38:01 -0700 (PDT) From: Florent Revest To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, yhs@fb.com, kpsingh@kernel.org, jackmanb@chromium.org, linux-kernel@vger.kernel.org, Florent Revest Subject: [PATCH bpf-next v3 2/6] bpf: Add a ARG_PTR_TO_CONST_STR argument type Date: Mon, 12 Apr 2021 17:37:50 +0200 Message-Id: <20210412153754.235500-3-revest@chromium.org> X-Mailer: git-send-email 2.31.1.295.g9ea45b61b8-goog In-Reply-To: <20210412153754.235500-1-revest@chromium.org> References: <20210412153754.235500-1-revest@chromium.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net This type provides the guarantee that an argument is going to be a const pointer to somewhere in a read-only map value. It also checks that this pointer is followed by a zero character before the end of the map value. Signed-off-by: Florent Revest Acked-by: Andrii Nakryiko --- include/linux/bpf.h | 1 + kernel/bpf/verifier.c | 41 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 42 insertions(+) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index ff8cd68c01b3..7d389eeee0b3 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -309,6 +309,7 @@ enum bpf_arg_type { ARG_PTR_TO_PERCPU_BTF_ID, /* pointer to in-kernel percpu type */ ARG_PTR_TO_FUNC, /* pointer to a bpf program function */ ARG_PTR_TO_STACK_OR_NULL, /* pointer to stack or NULL */ + ARG_PTR_TO_CONST_STR, /* pointer to a null terminated read-only string */ __BPF_ARG_TYPE_MAX, }; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 852541a435ef..5f46dd6f3383 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4787,6 +4787,7 @@ static const struct bpf_reg_types spin_lock_types = { .types = { PTR_TO_MAP_VALU static const struct bpf_reg_types percpu_btf_ptr_types = { .types = { PTR_TO_PERCPU_BTF_ID } }; static const struct bpf_reg_types func_ptr_types = { .types = { PTR_TO_FUNC } }; static const struct bpf_reg_types stack_ptr_types = { .types = { PTR_TO_STACK } }; +static const struct bpf_reg_types const_str_ptr_types = { .types = { PTR_TO_MAP_VALUE } }; static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = { [ARG_PTR_TO_MAP_KEY] = &map_key_value_types, @@ -4817,6 +4818,7 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = { [ARG_PTR_TO_PERCPU_BTF_ID] = &percpu_btf_ptr_types, [ARG_PTR_TO_FUNC] = &func_ptr_types, [ARG_PTR_TO_STACK_OR_NULL] = &stack_ptr_types, + [ARG_PTR_TO_CONST_STR] = &const_str_ptr_types, }; static int check_reg_type(struct bpf_verifier_env *env, u32 regno, @@ -5067,6 +5069,45 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, if (err) 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 (reg->type != PTR_TO_MAP_VALUE || !map || + !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); + 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 err;