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 4CADD268C6F; Tue, 3 Jun 2025 06:59:49 +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=1748933990; cv=none; b=cPCWzFToaTJFa9bsH9g6L1ZW6GFIF7l6O9ouffUzdwm6uBzvusbqAVLGCQq4cNU9uefsK97sCx30ZjsL0/azgP28Bx1IFATbW4Ashs+p+3lUQhl/NeipyvA/VI2UEdbqEqg34qgPtom34e2hf2/u8QH2OaDuRMzMRSQpjLDK7Cw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748933990; c=relaxed/simple; bh=D1DJb4SnUrqB3p+41jAzsi+WoB7vPnyoNcQiK6Opy5w=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pvBzhW0LiPYG/JsJiOtr1ha+OgdIx+ybyvmvCnpeKeY/Ca9dwDnbyH4ZWtDAhH6Lu5QKq5PjRQZqa/qCPOcHiJd/6yxnV83xIohICrIrr8b7+k3lJW3iloLejKuTU4knrHtHwC4XpBrHZJSH0+PJ3Zzbf+hgg/Wi2jVbsLFLGzs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ekutbj59; 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="ekutbj59" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8D88EC4CEED; Tue, 3 Jun 2025 06:59:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1748933989; bh=D1DJb4SnUrqB3p+41jAzsi+WoB7vPnyoNcQiK6Opy5w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ekutbj59Zl137NBCNx+l2QdKyupFi173NhNpFGfdiAWf+rt5Dii7sOiDV9D0QQAa3 +UsSoWijbSV0zEYneE9uYhfr0P38JgBfaG0FIgng255cuS15MG8d7AFIAsjjJl4lc3 OFNu4aixNU7TqrG4FBjNoEAoNcpMk0PlabDPqVPertK6/zc5rDgYPWcuKvBR2xq+QL bNfnHzleFJhn1fkmXixlInk6puxJIHlNVUT+UuWjEyaDbQDJnez+gGWCnP5dQC4yH2 Y9ky/bUKH/Ga7H3QjtmWlwniW7A/440X7WZzqdAeVXeWwADk4qiPUWfk5Hm14FbCqL EnVrXiWUesC1w== 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, m@maowtm.org, Song Liu Subject: [PATCH v2 bpf-next 3/4] bpf: Introduce path iterator Date: Mon, 2 Jun 2025 23:59:19 -0700 Message-ID: <20250603065920.3404510-4-song@kernel.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250603065920.3404510-1-song@kernel.org> References: <20250603065920.3404510-1-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 toward the root. This path iterator is based on path_walk_parent. A fixed zero'ed root is passed to path_walk_parent(). Therefore, unless the user terminates it earlier, the iterator will terminate at the real root. Signed-off-by: Song Liu --- kernel/bpf/Makefile | 1 + kernel/bpf/helpers.c | 3 +++ kernel/bpf/path_iter.c | 58 ++++++++++++++++++++++++++++++++++++++++++ kernel/bpf/verifier.c | 5 ++++ 4 files changed, 67 insertions(+) create mode 100644 kernel/bpf/path_iter.c diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile index 3a335c50e6e3..454a650d934e 100644 --- a/kernel/bpf/Makefile +++ b/kernel/bpf/Makefile @@ -56,6 +56,7 @@ obj-$(CONFIG_BPF_SYSCALL) += kmem_cache_iter.o ifeq ($(CONFIG_DMA_SHARED_BUFFER),y) obj-$(CONFIG_BPF_SYSCALL) += dmabuf_iter.o endif +obj-$(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 b71e428ad936..b190c78e40f6 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -3397,6 +3397,9 @@ BTF_ID_FLAGS(func, bpf_iter_dmabuf_next, KF_ITER_NEXT | KF_RET_NULL | KF_SLEEPAB BTF_ID_FLAGS(func, bpf_iter_dmabuf_destroy, KF_ITER_DESTROY | KF_SLEEPABLE) #endif BTF_ID_FLAGS(func, __bpf_trap) +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..0d972ec84beb --- /dev/null +++ b/kernel/bpf/path_iter.c @@ -0,0 +1,58 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */ +#include +#include +#include +#include + +/* open-coded iterator */ +struct bpf_iter_path { + __u64 __opaque[3]; +} __aligned(8); + +struct bpf_iter_path_kern { + struct path path; + __u64 flags; +} __aligned(8); + +__bpf_kfunc_start_defs(); + +__bpf_kfunc int bpf_iter_path_new(struct bpf_iter_path *it, + struct path *start, + __u64 flags) +{ + struct bpf_iter_path_kern *kit = (void *)it; + + BUILD_BUG_ON(sizeof(*kit) > sizeof(*it)); + BUILD_BUG_ON(__alignof__(*kit) != __alignof__(*it)); + + if (flags) { + memset(&kit->path, 0, sizeof(struct path)); + return -EINVAL; + } + + kit->path = *start; + path_get(&kit->path); + kit->flags = flags; + + return 0; +} + +__bpf_kfunc struct path *bpf_iter_path_next(struct bpf_iter_path *it) +{ + struct bpf_iter_path_kern *kit = (void *)it; + struct path root = {}; + + if (!path_walk_parent(&kit->path, &root)) + 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 a7d6e0c5928b..45b45cdfb223 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7036,6 +7036,10 @@ 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) @@ -7076,6 +7080,7 @@ 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