From mboxrd@z Thu Jan 1 00:00:00 1970 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 A063914E2F2; Wed, 28 May 2025 22:26:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748471203; cv=none; b=HZoLZFXF2FKN4AIVYEmnqi6UTR0ciYvoWFNX/oQNNA33/UvQLfwBE3nQ2hib9Jdp00BXnGTkaMA5APFePL/+dUTfnKrbOAlq21ZbPHUw9vcZmCWrhnUX1iGv+EqAdCEJJxx9jTtacOZj/EuXP6jXwZotgvH9V/qPsZGIS5m+89M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748471203; c=relaxed/simple; bh=OdqrPuaA4OShJbWqBysA33tbjRNwkLq+Lcj5uC8chRw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DhG5XEbm4tK9T/jG0Tf+/OGnh+5Bjm4tdp42i+9sCoEwu2wyQX7P+rZKPMR8jsUCJeftf0rWc9AYk7FHe+7NpTyLLMsz82OpuwfnUNiW9qgBo8cUSVip0hVFv7Ip/BCeuDaOHgQ90pDh4qjS8hjZ4udSx5tkOAr7sKJEmcZ5Frk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=eXtlXNir; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="eXtlXNir" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8C6DEC4CEE3; Wed, 28 May 2025 22:26:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1748471203; bh=OdqrPuaA4OShJbWqBysA33tbjRNwkLq+Lcj5uC8chRw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eXtlXNirxVoekee6vJsofDDUwl5f2fvXh5DbQGXKtPTBhYLvgsVoM+nvPMHTeR2HI Ykt1/QR7t8gSXGXxfa7HraVerReuWLL6a5pWbmx1QudYrq8O82/Lb2ANQEu/AxfWhz A+LaZ/bdNXNQnf53CisguYeb8ucXkBN2TiF/mXy8IkL4r1VD1BpPRRWmZM8L9ZcXRy IBokj6iVtmBpbcutaiPPS5ZtraJwLi32AML4laYCW0VDKHKp1UBYfKc2aG50Aj7TfL Cn7uFwbAb0eEkxbsKNSBMPXl07sAQVr9bNlBbAGV/eg+41MSp133gwbx10KyHLrN5e EPpEgJ3sG8eng== From: Song Liu To: bpf@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org Cc: kernel-team@meta.com, andrii@kernel.org, eddyz87@gmail.com, ast@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, kpsingh@kernel.org, mattbobrowski@google.com, amir73il@gmail.com, repnop@google.com, jlayton@kernel.org, josef@toxicpanda.com, mic@digikod.net, gnoack@google.com, Song Liu Subject: [PATCH bpf-next 3/4] bpf: Introduce path iterator Date: Wed, 28 May 2025 15:26:22 -0700 Message-ID: <20250528222623.1373000-4-song@kernel.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250528222623.1373000-1-song@kernel.org> References: <20250528222623.1373000-1-song@kernel.org> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Introduce a path iterator, which reliably walk a struct path. Current version only support walking towards the root, which helper path_parent. But the path iterator API can be extended to cover other use cases, for example, walking the mount tree. Signed-off-by: Song Liu --- kernel/bpf/Makefile | 1 + kernel/bpf/helpers.c | 3 ++ kernel/bpf/path_iter.c | 74 ++++++++++++++++++++++++++++++++++++++++++ kernel/bpf/verifier.c | 5 +++ 4 files changed, 83 insertions(+) create mode 100644 kernel/bpf/path_iter.c diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile index 70502f038b92..8075a83d5e08 100644 --- a/kernel/bpf/Makefile +++ b/kernel/bpf/Makefile @@ -53,6 +53,7 @@ obj-$(CONFIG_BPF_SYSCALL) += relo_core.o obj-$(CONFIG_BPF_SYSCALL) += btf_iter.o obj-$(CONFIG_BPF_SYSCALL) += btf_relocate.o obj-$(CONFIG_BPF_SYSCALL) += kmem_cache_iter.o +obj-$(CONFIG_BPF_SYSCALL) += path_iter.o CFLAGS_REMOVE_percpu_freelist.o = $(CC_FLAGS_FTRACE) CFLAGS_REMOVE_bpf_lru_list.o = $(CC_FLAGS_FTRACE) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index c1113b74e1e2..d77b055092e7 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -3386,6 +3386,9 @@ BTF_ID_FLAGS(func, bpf_copy_from_user_dynptr, KF_SLEEPABLE) BTF_ID_FLAGS(func, bpf_copy_from_user_str_dynptr, KF_SLEEPABLE) BTF_ID_FLAGS(func, bpf_copy_from_user_task_dynptr, KF_SLEEPABLE | KF_TRUSTED_ARGS) BTF_ID_FLAGS(func, bpf_copy_from_user_task_str_dynptr, KF_SLEEPABLE | KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_iter_path_new, KF_ITER_NEW | KF_SLEEPABLE) +BTF_ID_FLAGS(func, bpf_iter_path_next, KF_ITER_NEXT | KF_RET_NULL | KF_SLEEPABLE) +BTF_ID_FLAGS(func, bpf_iter_path_destroy, KF_ITER_DESTROY | KF_SLEEPABLE) BTF_KFUNCS_END(common_btf_ids) static const struct btf_kfunc_id_set common_kfunc_set = { diff --git a/kernel/bpf/path_iter.c b/kernel/bpf/path_iter.c new file mode 100644 index 000000000000..838ebbeac6c2 --- /dev/null +++ b/kernel/bpf/path_iter.c @@ -0,0 +1,74 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */ +#include +#include +#include +#include + +enum bpf_path_iter_mode { + BPF_PATH_ITER_MODE_PARENT = 1, +}; + +/* open-coded iterator */ +struct bpf_iter_path { + __u64 __opaque[3]; +} __aligned(8); + +struct bpf_iter_path_kern { + struct path path; + enum bpf_path_iter_mode mode; +} __aligned(8); + +__bpf_kfunc_start_defs(); + +__bpf_kfunc int bpf_iter_path_new(struct bpf_iter_path *it, + struct path *start, + enum bpf_path_iter_mode mode) +{ + struct bpf_iter_path_kern *kit = (void *)it; + + BUILD_BUG_ON(sizeof(*kit) > sizeof(*it)); + BUILD_BUG_ON(__alignof__(*kit) != __alignof__(*it)); + + kit->mode = mode; + + switch (mode) { + case BPF_PATH_ITER_MODE_PARENT: + break; + default: + memset(&kit->path, 0, sizeof(struct path)); + return -EINVAL; + } + + kit->path = *start; + path_get(&kit->path); + return 0; +} + +__bpf_kfunc struct path *bpf_iter_path_next(struct bpf_iter_path *it) +{ + struct bpf_iter_path_kern *kit = (void *)it; + + switch (kit->mode) { + case BPF_PATH_ITER_MODE_PARENT: + enum path_parent_status status = path_parent(&kit->path); + + /* If already at a root, return NULL */ + if (status == PATH_PARENT_REAL_ROOT || + status == PATH_PARENT_DISCONNECTED_ROOT) + return NULL; + break; + default: + return NULL; + } + return &kit->path; +} + +__bpf_kfunc void bpf_iter_path_destroy(struct bpf_iter_path *it) +{ + struct bpf_iter_path_kern *kit = (void *)it; + + path_put(&kit->path); +} + +__bpf_kfunc_end_defs(); diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index d5807d2efc92..734c06809563 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7034,6 +7034,10 @@ BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct socket) { struct sock *sk; }; +BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct path) { + struct dentry *dentry; +}; + static bool type_is_rcu(struct bpf_verifier_env *env, struct bpf_reg_state *reg, const char *field_name, u32 btf_id) @@ -7074,6 +7078,7 @@ static bool type_is_trusted_or_null(struct bpf_verifier_env *env, const char *field_name, u32 btf_id) { BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct socket)); + BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct path)); return btf_nested_type_is_trusted(&env->log, reg, field_name, btf_id, "__safe_trusted_or_null"); -- 2.47.1