From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-187.mta1.migadu.com (out-187.mta1.migadu.com [95.215.58.187]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CAC8B382392; Thu, 21 May 2026 03:24:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.187 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779333869; cv=none; b=I4SGQOEC4Za/fEgdDU++46WbRHexLgO0E8gGCFWbr8B9BQUzMesYlL+bPeMsUYYbt0NoJxSmIApIaGVeEYcMqggGSa2cA4tE2/SKPerNz0igtBvcl5sy0e+ogB47VzEocFxXpMEWWjUDjxzQEXusPRcwgDMdcopPXA5xv7IUk10= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779333869; c=relaxed/simple; bh=QF0VQigiS9C8x3qp/3dv7AfSItMP6oTWZARJW1nciTo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UyvJjzSG2e5NgIsi6wZ4PnkxxDnDtaKcVH5mmZNw6S/Fi/cqRo2HwN7HDjYM1JPSCyPD8fSBBNjjnzBdPmEyvgmFmCe1GBP/HZTVGGTlqtQ8xg5mPmKcFIOMIuZx/tCEx+E8hK9BErlLov6yJbNLfEDnSFKmrCsI9lXZO9Ku/fg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=QbmasXAN; arc=none smtp.client-ip=95.215.58.187 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="QbmasXAN" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1779333865; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+BjQ1+jDF+nnJfG5AqBJZDyfiRu75uMNz4SpIOWGGKo=; b=QbmasXANKZfP06EIaUAJG9KzxtXEnieFSZCWEw2jcu6As5oo+VnFdKSq2AWeWmUCf9RM/n mLLDYK6UQncQyoe+aPOoc0MIxtyC+huWp2OdUtPJ1D7167bLX/8sMfqw2GXQWo9ecS29gZ yF8FuqsEo2mlPM4AGfIDyqCybG7Etlc= From: Kaitao Cheng To: ast@kernel.org, corbet@lwn.net, martin.lau@linux.dev, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, chengkaitao@kylinos.cn, skhan@linuxfoundation.org, memxor@gmail.com Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, vmalik@redhat.com, linux-kselftest@vger.kernel.org Subject: [PATCH bpf-next v11 3/8] bpf: allow non-owning list-node args via __nonown_allowed Date: Thu, 21 May 2026 11:23:01 +0800 Message-ID: <20260521032306.97118-4-kaitao.cheng@linux.dev> In-Reply-To: <20260521032306.97118-1-kaitao.cheng@linux.dev> References: <20260521032306.97118-1-kaitao.cheng@linux.dev> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Kaitao Cheng KF_ARG_PTR_TO_LIST_NODE normally requires an owning reference (PTR_TO_BTF_ID | MEM_ALLOC with ref_obj_id). Introduce the __nonown_allowed annotation on selected list-node arguments so non-owning references with ref_obj_id==0 are accepted as well. This patch only adds the generic verifier support and documents the annotation. Later patches in the series will apply it to bpf_list_add /del(), and bpf_list_is_first/last(), allowing bpf_list_front/back() results to be used as the insertion point, deletion target, or query target for those kfuncs. Verifier keeps existing owning-ref checks by default; only arguments annotated with __nonown_allowed bypass MEM_ALLOC/ref_obj_id checks and then follow the same list-node validation path. Signed-off-by: Kaitao Cheng Reviewed-by: Eduard Zingerman --- Documentation/bpf/kfuncs.rst | 22 ++++++++++++++++++++-- kernel/bpf/verifier.c | 13 +++++++++++++ 2 files changed, 33 insertions(+), 2 deletions(-) diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst index 75e6c078e0e7..3a9db1108b95 100644 --- a/Documentation/bpf/kfuncs.rst +++ b/Documentation/bpf/kfuncs.rst @@ -207,8 +207,26 @@ Here, the buffer may be NULL. If the buffer is not NULL, it must be at least buffer__szk bytes in size. The kfunc is responsible for checking if the buffer is NULL before using it. -2.3.5 __str Annotation ----------------------------- +2.3.5 __nonown_allowed Annotation +--------------------------------- + +This annotation is used to indicate that the parameter may be a non-owning reference. + +An example is given below:: + + __bpf_kfunc int bpf_list_add(..., struct bpf_list_node + *prev__nonown_allowed, ...) + { + ... + } + +For the ``prev__nonown_allowed`` parameter (resolved as ``KF_ARG_PTR_TO_LIST_NODE``), +suffix ``__nonown_allowed`` retains the usual owning-pointer rules and also +permits a non-owning reference with no ref_obj_id (e.g. the return value of +bpf_list_front() / bpf_list_back()). + +2.3.6 __str Annotation +---------------------- This annotation is used to indicate that the argument is a constant string. An example is given below:: diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8dd79b735a69..f3cf8d85bea0 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10714,6 +10714,11 @@ static bool is_kfunc_arg_nullable(const struct btf *btf, const struct btf_param return btf_param_match_suffix(btf, arg, "__nullable"); } +static bool is_kfunc_arg_nonown_allowed(const struct btf *btf, const struct btf_param *arg) +{ + return btf_param_match_suffix(btf, arg, "__nonown_allowed"); +} + static bool is_kfunc_arg_const_str(const struct btf *btf, const struct btf_param *arg) { return btf_param_match_suffix(btf, arg, "__str"); @@ -12244,6 +12249,13 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ return ret; break; case KF_ARG_PTR_TO_LIST_NODE: + if (is_kfunc_arg_nonown_allowed(btf, &args[i]) && + type_is_non_owning_ref(reg->type) && !reg->ref_obj_id) { + /* Allow bpf_list_front/back return value for + * __nonown_allowed list-node arguments. + */ + goto check_ok; + } if (reg->type != (PTR_TO_BTF_ID | MEM_ALLOC)) { verbose(env, "%s expected pointer to allocated object\n", reg_arg_name(env, argno)); @@ -12253,6 +12265,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ verbose(env, "allocated object must be referenced\n"); return -EINVAL; } +check_ok: ret = process_kf_arg_ptr_to_list_node(env, reg, argno, meta); if (ret < 0) return ret; -- 2.50.1 (Apple Git-155)