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=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 CAA62C433ED for ; Mon, 19 Apr 2021 22:54:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9168E60FF1 for ; Mon, 19 Apr 2021 22:54:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229758AbhDSWyj (ORCPT ); Mon, 19 Apr 2021 18:54:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44580 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229681AbhDSWyi (ORCPT ); Mon, 19 Apr 2021 18:54:38 -0400 Received: from mail-pf1-x434.google.com (mail-pf1-x434.google.com [IPv6:2607:f8b0:4864:20::434]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42ABFC06174A; Mon, 19 Apr 2021 15:54:08 -0700 (PDT) Received: by mail-pf1-x434.google.com with SMTP id c17so24219147pfn.6; Mon, 19 Apr 2021 15:54:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=bL/C65cK5ETIOGRn+rp+8oiQf3Y9Nb4NWBAXa/S4YGg=; b=eUZmUJ9ybn8O+fcNkva++TF1ZumC95PpqJehEI16MwR08pmMiNhozdizhFfVoyaMbP Qwkt9kQCjpGQMnVWGRFzb31dvUx0xfuWI9sH3AtdIJ/yVMSuw/dgjvC84XUUsyDR9ocH u2iAT0uHkJxu323ZSCqw7lw+c6sw2qGxJuvcjf7kjgaczDZyuGoWdS/WUCQRtm9UL7jV ICfjE6gFh2k6NlidIOHy6IlwF49PnX9sUFZHt5ruAkGv6flkNzg9aLzks5v+rPBBcmAv 5NgdbDjsyOK612vaNe2KWaP1/mS1uoZwjOgGQwhnTLp4gzZenUxwk+wLdm2JWnAmfEVX QEGQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=bL/C65cK5ETIOGRn+rp+8oiQf3Y9Nb4NWBAXa/S4YGg=; b=knm3qHSUxFV8hZlBB/JaI9PZfAbXK/P6ibo6lrA6BmCL2Nianv42sWhIIxk8+jcwQI KOeZ756mxU9JlrWdjoQmUa0sKVlS6kjHtqdEh+NgX2yXRveInLdJZnFaQVT3OGOFKL3w AfROUTsCeKKh1xkbw/cVxANB9R5kBXe5Z+oKw8RhWr7Glcw1z9FDSh6VEtXxvfJmO70z wv2Cx+T011FF8jel6ZUJXmBnykNtwLF6/GWnX62uBL8YC1DT0XnV1UdfAtgHBiIrLmJt CXFuUovh8F8KbZ0w/fuCePsnCVayXdaRZ5qOlqkb6u+y3Y+Wq2TmL6oB0J4/v9G0uIiB XA9Q== X-Gm-Message-State: AOAM531g7fiIbSVzr4qImUq1TgIWHNnUvrQiEulceMrmKb8RjuR/YkBG klj0k0QW8t4jGLt3edF8SZs= X-Google-Smtp-Source: ABdhPJzFDsohB34RC6ivcKAPCb4xryxpRA9tFygXCORzvcBaEpKiYKMz7Ae+N9PsLwL0nePxCkLsZg== X-Received: by 2002:a63:2265:: with SMTP id t37mr13604890pgm.452.1618872847426; Mon, 19 Apr 2021 15:54:07 -0700 (PDT) Received: from ast-mbp.dhcp.thefacebook.com ([2620:10d:c090:400::5:948]) by smtp.gmail.com with ESMTPSA id z12sm4503040pfn.195.2021.04.19.15.54.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Apr 2021 15:54:06 -0700 (PDT) Date: Mon, 19 Apr 2021 15:54:04 -0700 From: Alexei Starovoitov To: Florent Revest Cc: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, yhs@fb.com, kpsingh@kernel.org, jackmanb@chromium.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH bpf-next v5 2/6] bpf: Add a ARG_PTR_TO_CONST_STR argument type Message-ID: <20210419225404.chlkiaku5vaxmmyh@ast-mbp.dhcp.thefacebook.com> References: <20210419155243.1632274-1-revest@chromium.org> <20210419155243.1632274-3-revest@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210419155243.1632274-3-revest@chromium.org> Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Mon, Apr 19, 2021 at 05:52:39PM +0200, 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 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 77d1d8c65b81..c160526fc8bf 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 || I think the 'type' check is redundant, since check_reg_type() did it via compatible_reg_types. If so it's probably better to remove it here ? '!map' looks unnecessary. Can it ever happen? If yes, it's a verifier bug. For example in check_mem_access() we just deref reg->map_ptr without checking which, I think, is correct. > + !bpf_map_is_rdonly(map)) { This check is needed, of course. > + 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) { since the code checks it here the same check in check_bpf_snprintf_call() should probably do: if (err) { verbose("verifier bug\n"); return -EFAULT; } instead of just "return err;" ? > + verbose(env, "direct value access on string failed\n"); I think the message doesn't tell users much, but they probably should never see it unless they try to do lookup from readonly array with more than one element. So I guess it's fine to keep this one as-is. Just flagging. Anyway the whole set looks great, so I've applied to bpf-next. Thanks!