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 A3FBAECAAA1 for ; Tue, 6 Sep 2022 02:34:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236536AbiIFCeB (ORCPT ); Mon, 5 Sep 2022 22:34:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44546 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231906AbiIFCd6 (ORCPT ); Mon, 5 Sep 2022 22:33:58 -0400 Received: from mail-io1-xd44.google.com (mail-io1-xd44.google.com [IPv6:2607:f8b0:4864:20::d44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0FDBA6B8F7; Mon, 5 Sep 2022 19:33:57 -0700 (PDT) Received: by mail-io1-xd44.google.com with SMTP id z72so7883007iof.12; Mon, 05 Sep 2022 19:33:57 -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:subject:date; bh=pzWkviLiyP7+AvZHEuuHIl7H6QCMlZET2vIM//Hw/N4=; b=OEnj2EUS5rA60Hck0t+m22Z32Zk7/RqXNxu0xBlXzGAK1Uj1jvylTAMNRCLWvBtyC4 oTt4HYZvfmv8K/PLRjUZUWHZlD4eBAHR9EX4FQ2rjkFxPJPQFcNSaUEhKzWE64kadAqA bmzld3jWov0YtVJ4zP6cgAGdcVVcA/lAYR485GnOlCtYvyXq/36aYJFUYjzbBmycWgR0 kK1WD/ApBm4DOg681fTICFFdZ/BKPPcMyW60cocFIYhqzggLQ7PqbmcrXdiv/RMIrejm FFUv5c8gvPQAI7yaU7vXjABwnczJVgpFKsEhopQl+Loe5/8UK1bK9bBc+9LBXorz/mnt TORw== 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:subject:date; bh=pzWkviLiyP7+AvZHEuuHIl7H6QCMlZET2vIM//Hw/N4=; b=Vbz1XzvtFFONbxJJB7sYErAOHsIXSNjoa0jMlIkRNaoPMmF5mGZTLmK6oZGz2pp+CC 4b3wURCr+6DtjkqORqbeOOo4TjzhU+QFhOzW7lkmJ8+0ujYp5btiKNduVHDuLHAHu1zV diQyLIcLQ0bK2tytY3b2dfeF0BA3vEPOz0aKpsnHmxJ+du4TTb5dzN5cypz5Zw/piph8 owmdGR5zyinB97HDPI5HpzIm9t7yEIJQ6Jui2kOBdwDq1hI20FAjZ6681YgOPEFUaRbI scnd7hFiATxK6hNHHcVXK1TqzVOuRyOVRLE4bC7pmHpnKNbJ57zNFVxbMBNRGt7PFVlO 5+nA== X-Gm-Message-State: ACgBeo3I5VDBOu/dhmlsnCdg0EfKHK2xhkgc54A5C5zmmrU05yJzpET7 t4pALXdcx9ogeoPJnTlBpZ3157TxFRgfTvZH2lGm29eGd2g= X-Google-Smtp-Source: AA6agR66aEKv92gUxUN2bgVUtBnJmMpf9wBd9vRPEuHyPMOyAAlTQVgq5S8qKe6sVX9yX077zcQXCJZr1DpRsBrFZag= X-Received: by 2002:a05:6602:2e94:b0:689:bae1:1b42 with SMTP id m20-20020a0566022e9400b00689bae11b42mr23885240iow.168.1662431636250; Mon, 05 Sep 2022 19:33:56 -0700 (PDT) MIME-Version: 1.0 References: <20220905143318.1592015-1-roberto.sassu@huaweicloud.com> <20220905143318.1592015-4-roberto.sassu@huaweicloud.com> In-Reply-To: <20220905143318.1592015-4-roberto.sassu@huaweicloud.com> From: Kumar Kartikeya Dwivedi Date: Tue, 6 Sep 2022 04:33:20 +0200 Message-ID: Subject: Re: [PATCH v16 03/12] btf: Allow dynamic pointer parameters 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, 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, 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 Mon, 5 Sept 2022 at 16:34, Roberto Sassu wrote: > > From: Roberto Sassu > > Allow dynamic pointers (struct bpf_dynptr_kern *) to be specified as > parameters in kfuncs. Also, ensure that dynamic pointers passed as argument > are valid and initialized, are a pointer to the stack, and of the type > local. More dynamic pointer types can be supported in the future. > > 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. > > To check if a dynamic pointer passed to the kfunc is valid and initialized, > and if its type is local, export the existing functions > is_dynptr_reg_valid_init() and is_dynptr_type_expected(). > > Cc: Joanne Koong > Cc: Kumar Kartikeya Dwivedi > Signed-off-by: Roberto Sassu > --- Acked-by: Kumar Kartikeya Dwivedi > include/linux/bpf_verifier.h | 5 +++++ > include/linux/btf.h | 9 +++++++++ > kernel/bpf/btf.c | 33 +++++++++++++++++++++++++++++++++ > kernel/bpf/verifier.c | 10 +++++----- > 4 files changed, 52 insertions(+), 5 deletions(-) > > diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h > index 1fdddbf3546b..dd58dfccd025 100644 > --- a/include/linux/bpf_verifier.h > +++ b/include/linux/bpf_verifier.h > @@ -571,6 +571,11 @@ 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); > +bool is_dynptr_type_expected(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..4266bff5fada 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 local 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 +6383,34 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, > return -EINVAL; > } > > + if (arg_dynptr) { > + if (reg->type != PTR_TO_STACK) { > + bpf_log(log, "arg#%d pointer type %s %s not to stack\n", > + i, btf_type_str(ref_t), > + ref_tname); > + return -EINVAL; > + } > + > + if (!is_dynptr_reg_valid_init(env, reg)) { > + bpf_log(log, > + "arg#%d pointer type %s %s must be valid and initialized\n", > + i, btf_type_str(ref_t), > + ref_tname); > + return -EINVAL; > + } > + > + if (!is_dynptr_type_expected(env, reg, > + ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_LOCAL)) { > + bpf_log(log, > + "arg#%d pointer type %s %s points to unsupported dynamic pointer type\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 10b3c0a81d09..8f02729074c6 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) > +bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, > + struct bpf_reg_state *reg) > { > struct bpf_func_state *state = func(env, reg); > int spi = get_spi(reg->off); > @@ -799,9 +799,9 @@ static bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, > return true; > } > > -static bool is_dynptr_type_expected(struct bpf_verifier_env *env, > - struct bpf_reg_state *reg, > - enum bpf_arg_type arg_type) > +bool is_dynptr_type_expected(struct bpf_verifier_env *env, > + struct bpf_reg_state *reg, > + enum bpf_arg_type arg_type) > { > struct bpf_func_state *state = func(env, reg); > enum bpf_dynptr_type dynptr_type; > -- > 2.25.1 >