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=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 66367C433E0 for ; Tue, 16 Mar 2021 01:04:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B5F164F72 for ; Tue, 16 Mar 2021 01:04:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234113AbhCPBDo (ORCPT ); Mon, 15 Mar 2021 21:03:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47354 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234106AbhCPBDY (ORCPT ); Mon, 15 Mar 2021 21:03:24 -0400 Received: from mail-yb1-xb2d.google.com (mail-yb1-xb2d.google.com [IPv6:2607:f8b0:4864:20::b2d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E3571C06174A; Mon, 15 Mar 2021 18:03:23 -0700 (PDT) Received: by mail-yb1-xb2d.google.com with SMTP id p186so35166299ybg.2; Mon, 15 Mar 2021 18:03:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=h66x3teGCQcy0fRIINxGcNQq5LSVOptp2d7+sCGalPg=; b=P/UYwD2MMOhepD71tPUDRUTJXkwNAxW5vxdOozDx10DaEu3WRWAlDVReo3PMd/T04x 4EhkJb0fNYwgu/Dhf/jZ4TTN9dv1rec6DMnpnUAHAOEv9JpkZbyAThXVS+pUwHWVHl/8 ZD2kZ/qbP+HrfaNkxfg2BqsK5ukIE0Y+HzGK0KH9Q4yKbmE7Vusm0I9+jp+baUMrmK5P qOxDIDnHMNc/lAjFuridXl7dmHDpNkNymLnavQj/CKMQpEltuGcgWJ3enX6/jQ42YjPh 3VEuX4OmRPTVXjmXdQ9oboBo/Umhb4ajR1G2y37NIpaWBTLbkBkHMWadQv9+O4DuVtZY KuEw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=h66x3teGCQcy0fRIINxGcNQq5LSVOptp2d7+sCGalPg=; b=KE/klCOepJSlNdIxltUkE7BvOOsFzseorxyLGphkdhT46eGAoGQs++KF6vQ7HNaqrC /ixBZxXLhin1lZegQZBT7YdOyC1HTvhw7FH01DBolSo8b5FCukN5u+Fri+J8wmblLMT2 cIlJGYVwjC4u+YcL1fSSf9pPqjV5UfBvc/yYjFZIJ/o09ATJwy+jP013l53dnN0+7+vD LFLVD/KmtdYn4SIJvyM6LKRfpCD7O019ZK88GfhXt3j1nGFptpHywvAKiWIFIxBik7cH Eid8HtnYcO0KEOXhkP/gyC6gZEPkjan+W/Iy6/Y9uTDnejDFvvkXHYnPedX9cmrtlxzd qtrw== X-Gm-Message-State: AOAM531ARhtNwO/BGPpJn7Avajee2OvOVhqEbwmsJzbKvLyNWt5mt/Pq vo7JT93JpLyx2nVgRldaLHwXlzdD5EQ9RJ/W53k= X-Google-Smtp-Source: ABdhPJx4ejUHcvIuxH2o66c6VqYPSfRhRg/7UXQzqOp41JiOSWvXHGFUkK77jkzGuOjsVEBUII5ctSxD57h9UdUFcLc= X-Received: by 2002:a25:3d46:: with SMTP id k67mr3298354yba.510.1615856603198; Mon, 15 Mar 2021 18:03:23 -0700 (PDT) MIME-Version: 1.0 References: <20210310220211.1454516-1-revest@chromium.org> <20210310220211.1454516-2-revest@chromium.org> In-Reply-To: <20210310220211.1454516-2-revest@chromium.org> From: Andrii Nakryiko Date: Mon, 15 Mar 2021 18:03:11 -0700 Message-ID: Subject: Re: [PATCH bpf-next 1/5] bpf: Add a ARG_PTR_TO_CONST_STR argument type To: Florent Revest Cc: bpf , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Yonghong Song , KP Singh , Brendan Jackman , open list Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 10, 2021 at 2:02 PM Florent Revest wrote: > > 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 NULL character before the end of the map value. > > Signed-off-by: Florent Revest > --- > 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 a25730eaa148..7b5319d75b3e 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -308,6 +308,7 @@ 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 f9096b049cd6..c99b2b67dc8d 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -4601,6 +4601,7 @@ 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, > @@ -4631,6 +4632,7 @@ 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, > @@ -4881,6 +4883,45 @@ 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, i; > + u64 map_addr; > + char *map_ptr; > + > + if (!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_helper_mem_access(env, regno, > + map->value_size - reg->off, > + false, meta); you expect reg to be PTR_TO_MAP_VALUE, so probably better to directly use check_map_access(). And double-check that register is of expected type. just the presence of ref->map_ptr might not be sufficient? > + 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) > + return err; > + > + map_ptr = (char *)(map_addr); map_ptr is a very confusing name. str_ptr or value ptr? > + for (i = map_off; map_ptr[i] != '\0'; i++) { > + if (i == map->value_size - 1) { use strnchr()? > + verbose(env, "map does not contain a NULL-terminated string\n"); map in the user-visible message is quite confusing, given that users will probably use this through static variables, so maybe just "string is not zero-terminated?" And it's not really a NULL, it's zero character. > + return -EACCES; > + } > + } > } > > return err; > -- > 2.30.1.766.gb4fecdf3b7-goog >