From patchwork Mon Oct 23 22:40:54 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Song Liu X-Patchwork-Id: 13433677 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4AEB8200AE; Mon, 23 Oct 2023 22:41:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="UPGhN8L2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1B12C433C7; Mon, 23 Oct 2023 22:41:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1698100889; bh=JktvCz8l5F4UfdnmLbTyIiMyqaaZHAVs4MnXWzRhxlA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UPGhN8L2dmDx0aw7J0oNrvoLopU1HKbVS+V6OwtP3K7qv788tHSQofo6ouQMCpUNB vW9Zcsbn53CMk8TR8xw36uDrWmiLHdsI5bo5GdCcLAwxeBo/bgyf3ZfKi6iJXvIdqF c3fAx8kqkFcsBm59vjEud6BTE8l9IGA+rkQXmlVl3eHNkVp0fd0vsflKvrtFDpmjh4 Qy8F+O9rRuVsXddy809fy7/wJ981tiAFYs3C7rWhsWs5i0kZ3ke+xzEQcvfliszU8r K2LTrqI7UE6an57vIwNUrQI/SHe8CNkoAbEgMhVob5XJRb3XalKoCyZl0EsbScMLki NCR9QfYPFw5fA== From: Song Liu To: bpf@vger.kernel.org, fsverity@lists.linux.dev Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, kernel-team@meta.com, ebiggers@kernel.org, tytso@mit.edu, roberto.sassu@huaweicloud.com, Song Liu Subject: [PATCH v4 bpf-next 3/9] bpf: Introduce KF_ARG_PTR_TO_CONST_STR Date: Mon, 23 Oct 2023 15:40:54 -0700 Message-Id: <20231023224100.2573116-4-song@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231023224100.2573116-1-song@kernel.org> References: <20231023224100.2573116-1-song@kernel.org> Precedence: bulk X-Mailing-List: fsverity@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 KF_ARG_PTR_TO_CONST_STR specifies kfunc args that point to const strings. This is similar to ARG_PTR_TO_CONST_STR for helpers. Signed-off-by: Song Liu --- Documentation/bpf/kfuncs.rst | 24 ++++++++++++++++++++++++ kernel/bpf/verifier.c | 19 +++++++++++++++++++ 2 files changed, 43 insertions(+) diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst index 0d2647fb358d..e696aca08b3a 100644 --- a/Documentation/bpf/kfuncs.rst +++ b/Documentation/bpf/kfuncs.rst @@ -137,6 +137,30 @@ Either way, the returned buffer is either NULL, or of size buffer_szk. Without t annotation, the verifier will reject the program if a null pointer is passed in with a nonzero size. +2.2.5 __const_str Annotation +---------------------------- +This annotation is used to indicate that the argument is a constant string. + +An example is given below:: + + __bpf_kfunc bpf_get_file_xattr(..., const char *name__const_str, ...) + { + ... + } + +In this case, ``bpf_get_file_xattr()`` can be called as:: + + bpf_get_file_xattr(..., "xattr_name", ...); + +Or:: + + const char name[] = "xattr_name"; /* This need to be global */ + int BPF_PROG(...) + { + ... + bpf_get_file_xattr(..., name, ...); + ... + } .. _BPF_kfunc_nodef: diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 6ce5f0fbad84..a2d992ca49c4 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10350,6 +10350,11 @@ static bool is_kfunc_arg_nullable(const struct btf *btf, const struct btf_param return __kfunc_param_match_suffix(btf, arg, "__nullable"); } +static bool is_kfunc_arg_const_str(const struct btf *btf, const struct btf_param *arg) +{ + return __kfunc_param_match_suffix(btf, arg, "__const_str"); +} + static bool is_kfunc_arg_scalar_with_name(const struct btf *btf, const struct btf_param *arg, const char *name) @@ -10493,6 +10498,7 @@ enum kfunc_ptr_arg_type { KF_ARG_PTR_TO_RB_ROOT, KF_ARG_PTR_TO_RB_NODE, KF_ARG_PTR_TO_NULL, + KF_ARG_PTR_TO_CONST_STR, }; enum special_kfunc_type { @@ -10637,6 +10643,9 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env, if (is_kfunc_arg_rbtree_node(meta->btf, &args[argno])) return KF_ARG_PTR_TO_RB_NODE; + if (is_kfunc_arg_const_str(meta->btf, &args[argno])) + return KF_ARG_PTR_TO_CONST_STR; + if ((base_type(reg->type) == PTR_TO_BTF_ID || reg2btf_ids[base_type(reg->type)])) { if (!btf_type_is_struct(ref_t)) { verbose(env, "kernel function %s args#%d pointer type %s %s is not supported\n", @@ -11260,6 +11269,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ case KF_ARG_PTR_TO_MEM_SIZE: case KF_ARG_PTR_TO_CALLBACK: case KF_ARG_PTR_TO_REFCOUNTED_KPTR: + case KF_ARG_PTR_TO_CONST_STR: /* Trusted by default */ break; default: @@ -11531,6 +11541,15 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ meta->arg_btf = reg->btf; meta->arg_btf_id = reg->btf_id; break; + case KF_ARG_PTR_TO_CONST_STR: + if (reg->type != PTR_TO_MAP_VALUE) { + verbose(env, "arg#%d doesn't point to a const string\n", i); + return -EINVAL; + } + ret = check_reg_const_str(env, reg, regno); + if (ret) + return ret; + break; } }