From patchwork Thu Nov 14 08:43:45 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Song Liu X-Patchwork-Id: 13874736 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 CA3F71F76AC; Thu, 14 Nov 2024 08:44:58 +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=1731573898; cv=none; b=VYu5q0QVbRObGVkoY4Z+IZ4k7xYBFEla+LS6IDH1/FtY76nWp3JbhvzAaJIYFbM2oT5GPExDqBNl1CdO/5fkxpLyqulbF87xKaJdSqTlHH3a5j0B7XVQUAYz08Qj2VU3JOhqV4OFWR9QL9T0zzA6sZVhyvtcgVOMNEc9J0uTIsE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731573898; c=relaxed/simple; bh=28xo/GcqXu7Noex43IdCT3nlsYOlGRCmbcULqotFvGU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tRNt5e4MLFRmXzBTqa4AefNEX1ju6U3G22UnDOvntle+32COSBrabD5YnZSsbWf2WOzopBDcDrbk45P+xYoaWc7ae/VMSkLwPtgh6AM6fgzoe5B/rRc+GoLe74Ou41a6rTnR0TSgmsT0CrAJzbFqJAh9kMyC0zoiqhe7XzqYk8U= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GI3AJpw4; 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="GI3AJpw4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C055DC4CECD; Thu, 14 Nov 2024 08:44:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1731573898; bh=28xo/GcqXu7Noex43IdCT3nlsYOlGRCmbcULqotFvGU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GI3AJpw4RFNXyKxSygIHCED2Kcme73S6J79kzh92/qStihHmAyX4Imu63z8x4UFeC mE817jtgRr4FjyaOyNHZnna9X69S1QYMsO+zDmaz7myxEQGU+pJwvf1CIRBWbinL8e yUgqeFZqYtCGphTg8k2s2UM48aW+bU0RCTPUEvo1RgONoVKWRRSok9116miCA5gbVK cBvGj8cPD8+zvcq5dfA9tojignWFQNzXnrzyOp2GdjKv05ktI/201cnV7QZZ2Vj9ZB X8WKJTpD/Fp9j+powCd7jhXziX0blEZUZutNng6/zbSpC4WN11HOd2WuvZXlLy6AMk aGVE8AufzG8yg== 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: [RFC/PATCH v2 bpf-next fanotify 7/7] selftests/bpf: Add test for BPF based fanotify fastpath handler Date: Thu, 14 Nov 2024 00:43:45 -0800 Message-ID: <20241114084345.1564165-8-song@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20241114084345.1564165-1-song@kernel.org> References: <20241114084345.1564165-1-song@kernel.org> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This test shows a simplified logic that monitors a subtree. This is simplified as it doesn't handle all the scenarios, such as: 1) moving a subsubtree into/outof the being monitoring subtree; 2) mount point inside the being monitored subtree Therefore, this is not to show a way to reliably monitor a subtree. Instead, this is to test the functionalities of bpf based fastpath. To really monitor a subtree reliably, we will need more complex logic. Overview of the logic: 1. fanotify is created for the whole file system (/tmp). 2. dentry of the subtree root is saved in map subtree_root. 3. bpf_is_subdir() is used to check whether a fanotify event happens inside the subtree. Only events happened in the subtree are passed to userspace. 4. A bpf map (inode_storage_map) is used to cache result from bpf_is_subdir(). 5. subsubtree moving is not handled. This is because we don't yet have a good way to walk a subtree from BPF (something similar to d_walk). Signed-off-by: Song Liu --- tools/testing/selftests/bpf/bpf_kfuncs.h | 5 + tools/testing/selftests/bpf/config | 2 + .../testing/selftests/bpf/prog_tests/fan_fp.c | 264 ++++++++++++++++++ tools/testing/selftests/bpf/progs/fan_fp.c | 154 ++++++++++ 4 files changed, 425 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/fan_fp.c create mode 100644 tools/testing/selftests/bpf/progs/fan_fp.c diff --git a/tools/testing/selftests/bpf/bpf_kfuncs.h b/tools/testing/selftests/bpf/bpf_kfuncs.h index 2eb3483f2fb0..6ccfef9685e1 100644 --- a/tools/testing/selftests/bpf/bpf_kfuncs.h +++ b/tools/testing/selftests/bpf/bpf_kfuncs.h @@ -87,4 +87,9 @@ struct dentry; */ extern int bpf_get_dentry_xattr(struct dentry *dentry, const char *name, struct bpf_dynptr *value_ptr) __ksym __weak; + +struct fanotify_fastpath_event; +extern struct inode *bpf_fanotify_data_inode(struct fanotify_fastpath_event *event) __ksym __weak; +extern void bpf_iput(struct inode *inode) __ksym __weak; +extern bool bpf_is_subdir(struct dentry *new_dentry, struct dentry *old_dentry) __ksym __weak; #endif diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config index 4ca84c8d9116..505327f53f07 100644 --- a/tools/testing/selftests/bpf/config +++ b/tools/testing/selftests/bpf/config @@ -24,6 +24,8 @@ CONFIG_DEBUG_INFO_BTF=y CONFIG_DEBUG_INFO_DWARF4=y CONFIG_DUMMY=y CONFIG_DYNAMIC_FTRACE=y +CONFIG_FANOTIFY=y +CONFIG_FANOTIFY_FASTPATH=y CONFIG_FPROBE=y CONFIG_FTRACE_SYSCALLS=y CONFIG_FUNCTION_ERROR_INJECTION=y diff --git a/tools/testing/selftests/bpf/prog_tests/fan_fp.c b/tools/testing/selftests/bpf/prog_tests/fan_fp.c new file mode 100644 index 000000000000..92929b811282 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/fan_fp.c @@ -0,0 +1,264 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */ + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +#include "fan_fp.skel.h" + +#define TEST_FS "/tmp/" +#define TEST_DIR "/tmp/fanotify_test/" + +static int create_test_subtree(void) +{ + int err; + + err = mkdir(TEST_DIR, 0777); + if (err && errno != EEXIST) + return err; + + return open(TEST_DIR, O_RDONLY); +} + +static int create_fanotify_fd(void) +{ + int fanotify_fd, err; + + fanotify_fd = fanotify_init(FAN_CLASS_NOTIF | FAN_REPORT_NAME | FAN_REPORT_DIR_FID, + O_RDONLY); + + if (!ASSERT_OK_FD(fanotify_fd, "fanotify_init")) + return -1; + + err = fanotify_mark(fanotify_fd, FAN_MARK_ADD | FAN_MARK_FILESYSTEM, + FAN_CREATE | FAN_OPEN | FAN_ONDIR | FAN_EVENT_ON_CHILD, + AT_FDCWD, TEST_FS); + if (!ASSERT_OK(err, "fanotify_mark")) { + close(fanotify_fd); + return -1; + } + + return fanotify_fd; +} + +static int attach_global_fastpath(int fanotify_fd) +{ + struct fanotify_fastpath_args args = { + .name = "_tmp_test_sub_tree", + .version = 1, + .flags = 0, + }; + + if (ioctl(fanotify_fd, FAN_IOC_ADD_FP, &args)) + return -1; + + return 0; +} + +#define EVENT_BUFFER_SIZE 4096 +struct file_access_result { + char name_prefix[16]; + bool accessed; +} access_results[3] = { + {"aa", false}, + {"bb", false}, + {"cc", false}, +}; + +static void update_access_results(char *name) +{ + int i; + + for (i = 0; i < ARRAY_SIZE(access_results); i++) { + if (strcmp(name, access_results[i].name_prefix) == 0) + access_results[i].accessed = true; + } +} + +static void parse_event(char *buffer, int len) +{ + struct fanotify_event_metadata *event = + (struct fanotify_event_metadata *) buffer; + struct fanotify_event_info_header *info; + struct fanotify_event_info_fid *fid; + struct file_handle *handle; + char *name; + int off; + + for (; FAN_EVENT_OK(event, len); event = FAN_EVENT_NEXT(event, len)) { + for (off = sizeof(*event) ; off < event->event_len; + off += info->len) { + info = (struct fanotify_event_info_header *) + ((char *) event + off); + switch (info->info_type) { + case FAN_EVENT_INFO_TYPE_DFID_NAME: + fid = (struct fanotify_event_info_fid *) info; + handle = (struct file_handle *)&fid->handle; + name = (char *)handle + sizeof(*handle) + handle->handle_bytes; + update_access_results(name); + break; + default: + break; + } + } + } +} + +static void touch_file(const char *path) +{ + int fd; + + fd = open(path, O_WRONLY|O_CREAT|O_NOCTTY|O_NONBLOCK, 0666); + if (!ASSERT_OK_FD(fd, "open")) + goto cleanup; + close(fd); +cleanup: + unlink(path); +} + +static void generate_and_test_event(int fanotify_fd, struct fan_fp *skel) +{ + char buffer[EVENT_BUFFER_SIZE]; + int len, err, fd; + + /* Open the dir, so initialize_subdir_root can work */ + fd = open(TEST_DIR, O_RDONLY); + close(fd); + + if (!ASSERT_EQ(skel->bss->initialized, true, "initialized")) + goto cleanup; + + /* access /tmp/fanotify_test/aa, this will generate event */ + touch_file(TEST_DIR "aa"); + + /* create /tmp/fanotify_test/subdir, this will get tag from the + * parent directory (added in the bpf program on fsnotify_mkdir) + */ + err = mkdir(TEST_DIR "subdir", 0777); + ASSERT_OK(err, "mkdir"); + + /* access /tmp/fanotify_test/subdir/bb, this will generate event */ + touch_file(TEST_DIR "subdir/bb"); + + /* access /tmp/cc, this will NOT generate event, as the BPF + * fastpath filtered this event out. (Because /tmp doesn't have + * the tag.) + */ + touch_file(TEST_FS "cc"); + + /* read and parse the events */ + len = read(fanotify_fd, buffer, EVENT_BUFFER_SIZE); + if (!ASSERT_GE(len, 0, "read event")) + goto cleanup; + parse_event(buffer, len); + + /* verify we generated events for aa and bb, but filtered out the + * event for cc. + */ + ASSERT_TRUE(access_results[0].accessed, "access aa"); + ASSERT_TRUE(access_results[1].accessed, "access bb"); + ASSERT_FALSE(access_results[2].accessed, "access cc"); + + /* Each touch_file() generates two events: FAN_CREATE then + * FAN_OPEN. The second event will hit cache. + * open(TEST_DIR) also hit cache, as we updated it cache for + * TEST_DIR from userspace. + * Therefore, we expect 4 cache hits: aa, bb, cc, and TEST_DIR. + */ + ASSERT_EQ(skel->bss->cache_hit, 4, "cache_hit"); + +cleanup: + rmdir(TEST_DIR "subdir"); + rmdir(TEST_DIR); +} + +/* This test shows a simplified logic that monitors a subtree. This is + * simplified as it doesn't handle all the scenarios, such as: + * + * 1) moving a subsubtree into/outof the being monitoring subtree; + * 2) mount point inside the being monitored subtree + * + * Therefore, this is not to show a way to reliably monitor a subtree. + * Instead, this is to test the functionalities of bpf based fastpath. + * + * Overview of the logic: + * 1. fanotify is created for the whole file system (/tmp); + * 2. A bpf map (inode_storage_map) is used to tag directories to + * monitor (starting from /tmp/fanotify_test); + * 3. On fsnotify_mkdir, thee tag is propagated to newly created sub + * directories (/tmp/fanotify_test/subdir); + * 4. The bpf fastpath checks whether the event happens in a directory + * with the tag. If yes, the event is sent to user space; otherwise, + * the event is dropped. + */ +static void test_monitor_subtree(void) +{ + struct bpf_link *link; + struct fan_fp *skel; + int test_root_fd; + int zero = 0; + int err, fanotify_fd; + struct stat st; + + test_root_fd = create_test_subtree(); + + if (!ASSERT_OK_FD(test_root_fd, "create_test_subtree")) + return; + + err = fstat(test_root_fd, &st); + if (!ASSERT_OK(err, "fstat test_root_fd")) + goto close_test_root_fd; + + skel = fan_fp__open_and_load(); + + if (!ASSERT_OK_PTR(skel, "fan_fp__open_and_load")) + goto close_test_root_fd; + + skel->bss->root_ino = st.st_ino; + + /* Add tag to /tmp/fanotify_test/ */ + err = bpf_map_update_elem(bpf_map__fd(skel->maps.inode_storage_map), + &test_root_fd, &zero, BPF_ANY); + if (!ASSERT_OK(err, "bpf_map_update_elem")) + goto destroy_skel; + link = bpf_map__attach_struct_ops(skel->maps.bpf_fanotify_fastpath_ops); + if (!ASSERT_OK_PTR(link, "bpf_map__attach_struct_ops")) + goto destroy_skel; + + fanotify_fd = create_fanotify_fd(); + if (!ASSERT_OK_FD(fanotify_fd, "create_fanotify_fd")) + goto destroy_link; + + err = attach_global_fastpath(fanotify_fd); + if (!ASSERT_OK(err, "attach_global_fastpath")) + goto close_fanotify_fd; + + generate_and_test_event(fanotify_fd, skel); + +close_fanotify_fd: + close(fanotify_fd); + +destroy_link: + bpf_link__destroy(link); +destroy_skel: + fan_fp__destroy(skel); + +close_test_root_fd: + close(test_root_fd); + rmdir(TEST_DIR); +} + +void test_bpf_fanotify_fastpath(void) +{ + if (test__start_subtest("subtree")) + test_monitor_subtree(); +} diff --git a/tools/testing/selftests/bpf/progs/fan_fp.c b/tools/testing/selftests/bpf/progs/fan_fp.c new file mode 100644 index 000000000000..97e7d0b9e644 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/fan_fp.c @@ -0,0 +1,154 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */ + +#include "vmlinux.h" +#include +#include +#include "bpf_kfuncs.h" + +struct __dentry_kptr_value { + struct dentry __kptr * dentry; +}; + +/* subdir_root map holds a single dentry pointer to the subtree root. + * This pointer is used to call bpf_is_subdir(). + */ +struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __type(key, int); + __type(value, struct __dentry_kptr_value); + __uint(max_entries, 1); +} subdir_root SEC(".maps"); + +/* inode_storage_map serves as cache for bpf_is_subdir(). inode local + * storage has O(1) access time. So this is preferred over calling + * bpf_is_subdir(). + */ +struct { + __uint(type, BPF_MAP_TYPE_INODE_STORAGE); + __uint(map_flags, BPF_F_NO_PREALLOC); + __type(key, int); + __type(value, int); +} inode_storage_map SEC(".maps"); + +unsigned long root_ino; +bool initialized; + +/* This function initialize map subdir_root. The logic is a bit ungly. + * First, user space sets root_ino. Then a fanotify event is triggered. + * If the event dentry matches root_ino, we take a reference on the + * dentry and save it in subdir_root map. The reference will be freed on + * the termination of subdir_root map. + */ +static void initialize_subdir_root(struct fanotify_fastpath_event *fp_event) +{ + struct __dentry_kptr_value *v; + struct dentry *dentry, *old; + int zero = 0; + + if (initialized) + return; + + dentry = bpf_fanotify_data_dentry(fp_event); + if (!dentry) + return; + + if (dentry->d_inode->i_ino != root_ino) { + bpf_dput(dentry); + return; + } + + v = bpf_map_lookup_elem(&subdir_root, &zero); + if (!v) { + bpf_dput(dentry); + return; + } + + old = bpf_kptr_xchg(&v->dentry, dentry); + if (old) + bpf_dput(old); + initialized = true; +} + +int cache_hit; + +/* bpf_fp_handler is sleepable, as it calls bpf_dput() */ +SEC("struct_ops.s") +int BPF_PROG(bpf_fp_handler, + struct fsnotify_group *group, + struct fanotify_fastpath_hook *fp_hook, + struct fanotify_fastpath_event *fp_event) +{ + struct __dentry_kptr_value *v; + struct dentry *dentry; + int zero = 0; + int *value; + int ret; + + initialize_subdir_root(fp_event); + + /* Before the subdir_root map is initialized, send all events to + * user space. + */ + if (!initialized) + return FAN_FP_RET_SEND_TO_USERSPACE; + + dentry = bpf_fanotify_data_dentry(fp_event); + if (!dentry) + return FAN_FP_RET_SEND_TO_USERSPACE; + + /* If inode_storage_map has cached value, just return it */ + value = bpf_inode_storage_get(&inode_storage_map, dentry->d_inode, 0, 0); + if (value) { + bpf_dput(dentry); + cache_hit++; + return *value; + } + + /* Hold rcu read lock for bpf_is_subdir */ + bpf_rcu_read_lock(); + v = bpf_map_lookup_elem(&subdir_root, &zero); + if (!v || !v->dentry) { + /* This shouldn't happen, but we need this to pass + * the verifier. + */ + ret = FAN_FP_RET_SEND_TO_USERSPACE; + goto out; + } + + if (bpf_is_subdir(dentry, v->dentry)) + ret = FAN_FP_RET_SEND_TO_USERSPACE; + else + ret = FAN_FP_RET_SKIP_EVENT; +out: + bpf_rcu_read_unlock(); + + /* Save current result to the inode_storage_map */ + value = bpf_inode_storage_get(&inode_storage_map, dentry->d_inode, 0, + BPF_LOCAL_STORAGE_GET_F_CREATE); + if (value) + *value = ret; + bpf_dput(dentry); + return ret; +} + +SEC("struct_ops") +int BPF_PROG(bpf_fp_init, struct fanotify_fastpath_hook *hook, const char *args) +{ + return 0; +} + +SEC("struct_ops") +void BPF_PROG(bpf_fp_free, struct fanotify_fastpath_hook *hook) +{ +} + +SEC(".struct_ops.link") +struct fanotify_fastpath_ops bpf_fanotify_fastpath_ops = { + .fp_handler = (void *)bpf_fp_handler, + .fp_init = (void *)bpf_fp_init, + .fp_free = (void *)bpf_fp_free, + .name = "_tmp_test_sub_tree", +}; + +char _license[] SEC("license") = "GPL";