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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 28669ECAAD7 for ; Fri, 26 Aug 2022 20:37:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344981AbiHZUhg (ORCPT ); Fri, 26 Aug 2022 16:37:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38494 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245076AbiHZUhY (ORCPT ); Fri, 26 Aug 2022 16:37:24 -0400 Received: from mail-il1-x141.google.com (mail-il1-x141.google.com [IPv6:2607:f8b0:4864:20::141]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF17AC88BF; Fri, 26 Aug 2022 13:37:22 -0700 (PDT) Received: by mail-il1-x141.google.com with SMTP id l16so1197630ilj.2; Fri, 26 Aug 2022 13:37:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc; bh=WEfgf2R2DJCDs4AKod2m6jqCNNrqV7+4FPWOEmxw+3A=; b=g8/kHbdWdljV6lk39scxyK+hjzhO3FYwd+XGwNJZSS856AA3+YYk0umH9HZ2LQ6uB1 WgVaK5PwdsQ4LiW812qON8c6Lx5eUGHVubtjTD5u0hDQtXh16kAo3KEv1zlgaCOhhzBZ aw+xNrIqGMF7r6CEzA/j3mIJI+hnI/gvDWIiajFuVI5BoTQmSIXCljz9nWGiyN6lZRCx PIWXK/Bv8B/IzdU7tOFT+Sa/UEuD/mkg/t5lEi7aD5ZXABQsnwjdWJiRy6BhYpIDgfZN 4TtcQHkXszBxP8tDrpf76uB+CXJzfS+TItNBtHR77cghkhpqhqwF+Hm8dER/JoTWsIYS IpuQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc; bh=WEfgf2R2DJCDs4AKod2m6jqCNNrqV7+4FPWOEmxw+3A=; b=A40NbiAGR/Uo1y4UkgWTgeONHF4uPBZPyv5QDDiaiP/CRD/vrwVLtQyxF6h8S37EbP 3NIbaCqNaqBQxVG5OtGUggzqQAmIP2YV7Cw1zRWlLB+7rtIOvFDRZmlhxzd/2GJ+0RQh hlDNHXMJIzDiqGPRL1cU3zBhyEe24WsDLmWxEZ5sAfaZL05mXtI8iIOzoO6bBLlaguBx f16gBU8igqrGeZX2DVIS6fPMAAsviTKiVvoUxrwVbd8TU4ee9VCmBQXROuTKqB0ssX4e PW0r2m+rUV5Vx6/WD9/hvJnCR0cR5yGb3lh/i2FW1pu28Ty6SKFyLOUz4nyGhOxM0pXG DQHg== X-Gm-Message-State: ACgBeo0Q3n7uSbbnHuTKlV5dpiCqh9VzwcYPMpCMKWTZUnfu6s2qPnRr Bwfk6ZAgn/cUYHA7M3ivlm4N4ivU34NHPOq64EY= X-Google-Smtp-Source: AA6agR4OuuzyTi2F9/KR+kfMeIwGonZgjsgtKhvQSq79lYto57sei+AOJAhU1Hd0a9qqnDRUs5bZS+vBJFX5D/QZkG4= X-Received: by 2002:a92:ca4e:0:b0:2ea:3f77:a85 with SMTP id q14-20020a92ca4e000000b002ea3f770a85mr4787935ilo.219.1661546241807; Fri, 26 Aug 2022 13:37:21 -0700 (PDT) MIME-Version: 1.0 References: <20220823150035.711534-1-roberto.sassu@huaweicloud.com> <20220823150035.711534-3-roberto.sassu@huaweicloud.com> In-Reply-To: <20220823150035.711534-3-roberto.sassu@huaweicloud.com> From: Kumar Kartikeya Dwivedi Date: Fri, 26 Aug 2022 22:36:46 +0200 Message-ID: Subject: Re: [PATCH v13 02/10] btf: Handle dynamic pointer parameter in kfuncs To: Roberto Sassu Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, mykolal@fb.com, corbet@lwn.net, dhowells@redhat.com, jarkko@kernel.org, rostedt@goodmis.org, mingo@redhat.com, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, shuah@kernel.org, bpf@vger.kernel.org, linux-doc@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, deso@posteo.net, Roberto Sassu , Joanne Koong Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 23 Aug 2022 at 19:27, Roberto Sassu wrote: > > From: Roberto Sassu > > Allow the bpf_dynptr_kern parameter to be specified in kfuncs. Also, ensure > that the dynamic pointer is valid and initialized. > > To properly detect whether a parameter is of the desired type, introduce > the stringify_struct() macro to compare the returned structure name with > the desired name. In addition, protect against structure renames, by > halting the build with BUILD_BUG_ON(), so that developers have to revisit > the code. > > Cc: Joanne Koong > Signed-off-by: Roberto Sassu > --- > include/linux/bpf_verifier.h | 3 +++ > include/linux/btf.h | 9 +++++++++ > kernel/bpf/btf.c | 18 ++++++++++++++++++ > kernel/bpf/verifier.c | 4 ++-- > 4 files changed, 32 insertions(+), 2 deletions(-) > > diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h > index 2e3bad8640dc..55876fbdbae2 100644 > --- a/include/linux/bpf_verifier.h > +++ b/include/linux/bpf_verifier.h > @@ -560,6 +560,9 @@ 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); > +bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, > + struct bpf_reg_state *reg, > + enum bpf_arg_type arg_type); > > /* 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/include/linux/btf.h b/include/linux/btf.h > index ad93c2d9cc1c..f546d368ac5d 100644 > --- a/include/linux/btf.h > +++ b/include/linux/btf.h > @@ -52,6 +52,15 @@ > #define KF_SLEEPABLE (1 << 5) /* kfunc may sleep */ > #define KF_DESTRUCTIVE (1 << 6) /* kfunc performs destructive actions */ > > +/* > + * Return the name of the passed struct, if exists, or halt the build if for > + * example the structure gets renamed. In this way, developers have to revisit > + * the code using that structure name, and update it accordingly. > + */ > +#define stringify_struct(x) \ > + ({ BUILD_BUG_ON(sizeof(struct x) < 0); \ > + __stringify(x); }) > + > struct btf; > struct btf_member; > struct btf_type; > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c > index e49b3b6d48ad..26cb548420af 100644 > --- a/kernel/bpf/btf.c > +++ b/kernel/bpf/btf.c > @@ -6362,15 +6362,20 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, > > if (is_kfunc) { > bool arg_mem_size = i + 1 < nargs && is_kfunc_arg_mem_size(btf, &args[i + 1], ®s[regno + 1]); > + bool arg_dynptr = btf_type_is_struct(ref_t) && > + !strcmp(ref_tname, > + stringify_struct(bpf_dynptr_kern)); > > /* Permit pointer to mem, but only when argument > * type is pointer to scalar, or struct composed > * (recursively) of scalars. > * When arg_mem_size is true, the pointer can be > * void *. > + * Also permit initialized dynamic pointers. > */ > if (!btf_type_is_scalar(ref_t) && > !__btf_type_is_scalar_struct(log, btf, ref_t, 0) && > + !arg_dynptr && > (arg_mem_size ? !btf_type_is_void(ref_t) : 1)) { > bpf_log(log, > "arg#%d pointer type %s %s must point to %sscalar, or struct with scalar\n", > @@ -6378,6 +6383,19 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, > return -EINVAL; > } > > + if (arg_dynptr) { > + if (!is_dynptr_reg_valid_init(env, reg, > + ARG_PTR_TO_DYNPTR)) { Do you intend to really accept all kinds of dynptr here? In the future we will get more, and by default ARG_PTR_TO_DYNPTR accepts all, so it seems better to start with a small strict subset. Secondly, you need to also check whether reg is a PTR_TO_STACK inside this arg_dynptr branch. It is incorrect to call is_dynptr_reg_valid_init for any other type of register. It would also be nice to include some tests for that. > + bpf_log(log, > + "arg#%d pointer type %s %s must be initialized\n", > + i, btf_type_str(ref_t), > + ref_tname); > + return -EINVAL; > + } > + > + continue; > + } > + > /* Check for mem, len pair */ > if (arg_mem_size) { > if (check_kfunc_mem_size_reg(env, ®s[regno + 1], regno + 1)) { > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 2c1f8069f7b7..aa834e7bb296 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -779,8 +779,8 @@ static bool is_dynptr_reg_valid_uninit(struct bpf_verifier_env *env, struct bpf_ > return true; > } > > -static bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, struct bpf_reg_state *reg, > - enum bpf_arg_type arg_type) > +bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, struct bpf_reg_state *reg, > + enum bpf_arg_type arg_type) > { > struct bpf_func_state *state = func(env, reg); > int spi = get_spi(reg->off); > -- > 2.25.1 >