/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include #include #include "alloc-util.h" #include "bpf-program.h" #include "errno-util.h" #include "escape.h" #include "fd-util.h" #include "memory-util.h" #include "missing_syscall.h" #include "path-util.h" #include "serialize.h" #include "string-table.h" static const char *const bpf_cgroup_attach_type_table[__MAX_BPF_ATTACH_TYPE] = { [BPF_CGROUP_INET_INGRESS] = "ingress", [BPF_CGROUP_INET_EGRESS] = "egress", [BPF_CGROUP_INET_SOCK_CREATE] = "sock_create", [BPF_CGROUP_SOCK_OPS] = "sock_ops", [BPF_CGROUP_DEVICE] = "device", [BPF_CGROUP_INET4_BIND] = "bind4", [BPF_CGROUP_INET6_BIND] = "bind6", [BPF_CGROUP_INET4_CONNECT] = "connect4", [BPF_CGROUP_INET6_CONNECT] = "connect6", [BPF_CGROUP_INET4_POST_BIND] = "post_bind4", [BPF_CGROUP_INET6_POST_BIND] = "post_bind6", [BPF_CGROUP_UDP4_SENDMSG] = "sendmsg4", [BPF_CGROUP_UDP6_SENDMSG] = "sendmsg6", [BPF_CGROUP_SYSCTL] = "sysctl", [BPF_CGROUP_UDP4_RECVMSG] = "recvmsg4", [BPF_CGROUP_UDP6_RECVMSG] = "recvmsg6", [BPF_CGROUP_GETSOCKOPT] = "getsockopt", [BPF_CGROUP_SETSOCKOPT] = "setsockopt", }; DEFINE_STRING_TABLE_LOOKUP(bpf_cgroup_attach_type, int); DEFINE_HASH_OPS_WITH_KEY_DESTRUCTOR(bpf_program_hash_ops, void, trivial_hash_func, trivial_compare_func, bpf_program_free); BPFProgram *bpf_program_free(BPFProgram *p) { if (!p) return NULL; /* Unfortunately, the kernel currently doesn't implicitly detach BPF programs from their cgroups when the last * fd to the BPF program is closed. This has nasty side-effects since this means that abnormally terminated * programs that attached one of their BPF programs to a cgroup will leave this program pinned for good with * zero chance of recovery, until the cgroup is removed. This is particularly problematic if the cgroup in * question is the root cgroup (or any other cgroup belonging to a service that cannot be restarted during * operation, such as dbus), as the memory for the BPF program can only be reclaimed through a reboot. To * counter this, we track closely to which cgroup a program was attached to and will detach it on our own * whenever we close the BPF fd. */ (void) bpf_program_cgroup_detach(p); safe_close(p->kernel_fd); free(p->prog_name); free(p->instructions); free(p->attached_path); return mfree(p); } /* struct bpf_prog_info info must be initialized since its value is both input and output * for BPF_OBJ_GET_INFO_BY_FD syscall. */ static int bpf_program_get_info_by_fd(int prog_fd, struct bpf_prog_info *info, uint32_t info_len) { union bpf_attr attr; /* Explicitly memset to zero since some compilers may produce non-zero-initialized padding when * structured initialization is used. * Refer to https://github.com/systemd/systemd/issues/18164 */ zero(attr); attr.info.bpf_fd = prog_fd; attr.info.info_len = info_len; attr.info.info = PTR_TO_UINT64(info); return RET_NERRNO(bpf(BPF_OBJ_GET_INFO_BY_FD, &attr, sizeof(attr))); } int bpf_program_new(uint32_t prog_type, const char *prog_name, BPFProgram **ret) { _cleanup_(bpf_program_freep) BPFProgram *p = NULL; _cleanup_free_ char *name = NULL; if (prog_name) { if (strlen(prog_name) >= BPF_OBJ_NAME_LEN) return -ENAMETOOLONG; name = strdup(prog_name); if (!name) return -ENOMEM; } p = new(BPFProgram, 1); if (!p) return -ENOMEM; *p = (BPFProgram) { .prog_type = prog_type, .kernel_fd = -1, .prog_name = TAKE_PTR(name), }; *ret = TAKE_PTR(p); return 0; } int bpf_program_new_from_bpffs_path(const char *path, BPFProgram **ret) { _cleanup_(bpf_program_freep) BPFProgram *p = NULL; struct bpf_prog_info info = {}; int r; assert(path); assert(ret); p = new(BPFProgram, 1); if (!p) return -ENOMEM; *p = (BPFProgram) { .prog_type = BPF_PROG_TYPE_UNSPEC, .kernel_fd = -1, }; r = bpf_program_load_from_bpf_fs(p, path); if (r < 0) return r; r = bpf_program_get_info_by_fd(p->kernel_fd, &info, sizeof(info)); if (r < 0) return r; p->prog_type = info.type; *ret = TAKE_PTR(p); return 0; } int bpf_program_add_instructions(BPFProgram *p, const struct bpf_insn *instructions, size_t count) { assert(p); if (p->kernel_fd >= 0) /* don't allow modification after we uploaded things to the kernel */ return -EBUSY; if (!GREEDY_REALLOC(p->instructions, p->n_instructions + count)) return -ENOMEM; memcpy(p->instructions + p->n_instructions, instructions, sizeof(struct bpf_insn) * count); p->n_instructions += count; return 0; } int bpf_program_load_kernel(BPFProgram *p, char *log_buf, size_t log_size) { union bpf_attr attr; assert(p); if (p->kernel_fd >= 0) { /* make this idempotent */ memzero(log_buf, log_size); return 0; } // FIXME: Clang doesn't 0-pad with structured initialization, causing // the kernel to reject the bpf_attr as invalid. See: // https://github.com/torvalds/linux/blob/v5.9/kernel/bpf/syscall.c#L65 // Ideally it should behave like GCC, so that we can remove these workarounds. zero(attr); attr.prog_type = p->prog_type; attr.insns = PTR_TO_UINT64(p->instructions); attr.insn_cnt = p->n_instructions; attr.license = PTR_TO_UINT64("GPL"); attr.log_buf = PTR_TO_UINT64(log_buf); attr.log_level = !!log_buf; attr.log_size = log_size; if (p->prog_name) strncpy(attr.prog_name, p->prog_name, BPF_OBJ_NAME_LEN - 1); p->kernel_fd = bpf(BPF_PROG_LOAD, &attr, sizeof(attr)); if (p->kernel_fd < 0) return -errno; return 0; } int bpf_program_load_from_bpf_fs(BPFProgram *p, const char *path) { union bpf_attr attr; assert(p); if (p->kernel_fd >= 0) /* don't overwrite an assembled or loaded program */ return -EBUSY; zero(attr); attr.pathname = PTR_TO_UINT64(path); p->kernel_fd = bpf(BPF_OBJ_GET, &attr, sizeof(attr)); if (p->kernel_fd < 0) return -errno; return 0; } int bpf_program_cgroup_attach(BPFProgram *p, int type, const char *path, uint32_t flags) { _cleanup_free_ char *copy = NULL; _cleanup_close_ int fd = -1; union bpf_attr attr; int r; assert(p); assert(type >= 0); assert(path); if (!IN_SET(flags, 0, BPF_F_ALLOW_OVERRIDE, BPF_F_ALLOW_MULTI)) return -EINVAL; /* We need to track which cgroup the program is attached to, and we can only track one attachment, hence let's * refuse this early. */ if (p->attached_path) { if (!path_equal(p->attached_path, path)) return -EBUSY; if (p->attached_type != type) return -EBUSY; if (p->attached_flags != flags) return -EBUSY; /* Here's a shortcut: if we previously attached this program already, then we don't have to do so * again. Well, with one exception: if we are in BPF_F_ALLOW_OVERRIDE mode then someone else might have * replaced our program since the last time, hence let's reattach it again, just to be safe. In flags * == 0 mode this is not an issue since nobody else can replace our program in that case, and in flags * == BPF_F_ALLOW_MULTI mode any other's program would be installed in addition to ours hence ours * would remain in effect. */ if (flags != BPF_F_ALLOW_OVERRIDE) return 0; } /* Ensure we have a kernel object for this. */ r = bpf_program_load_kernel(p, NULL, 0); if (r < 0) return r; copy = strdup(path); if (!copy) return -ENOMEM; fd = open(path, O_DIRECTORY|O_RDONLY|O_CLOEXEC); if (fd < 0) return -errno; zero(attr); attr.attach_type = type; attr.target_fd = fd; attr.attach_bpf_fd = p->kernel_fd; attr.attach_flags = flags; if (bpf(BPF_PROG_ATTACH, &attr, sizeof(attr)) < 0) return -errno; free_and_replace(p->attached_path, copy); p->attached_type = type; p->attached_flags = flags; return 0; } int bpf_program_cgroup_detach(BPFProgram *p) { _cleanup_close_ int fd = -1; assert(p); if (!p->attached_path) return -EUNATCH; fd = open(p->attached_path, O_DIRECTORY|O_RDONLY|O_CLOEXEC); if (fd < 0) { if (errno != ENOENT) return -errno; /* If the cgroup does not exist anymore, then we don't have to explicitly detach, it got detached * implicitly by the removal, hence don't complain */ } else { union bpf_attr attr; zero(attr); attr.attach_type = p->attached_type; attr.target_fd = fd; attr.attach_bpf_fd = p->kernel_fd; if (bpf(BPF_PROG_DETACH, &attr, sizeof(attr)) < 0) return -errno; } p->attached_path = mfree(p->attached_path); return 0; } int bpf_map_new(enum bpf_map_type type, size_t key_size, size_t value_size, size_t max_entries, uint32_t flags) { union bpf_attr attr; zero(attr); attr.map_type = type; attr.key_size = key_size; attr.value_size = value_size; attr.max_entries = max_entries; attr.map_flags = flags; return RET_NERRNO(bpf(BPF_MAP_CREATE, &attr, sizeof(attr))); } int bpf_map_update_element(int fd, const void *key, void *value) { union bpf_attr attr; zero(attr); attr.map_fd = fd; attr.key = PTR_TO_UINT64(key); attr.value = PTR_TO_UINT64(value); return RET_NERRNO(bpf(BPF_MAP_UPDATE_ELEM, &attr, sizeof(attr))); } int bpf_map_lookup_element(int fd, const void *key, void *value) { union bpf_attr attr; zero(attr); attr.map_fd = fd; attr.key = PTR_TO_UINT64(key); attr.value = PTR_TO_UINT64(value); return RET_NERRNO(bpf(BPF_MAP_LOOKUP_ELEM, &attr, sizeof(attr))); } int bpf_program_pin(int prog_fd, const char *bpffs_path) { union bpf_attr attr; zero(attr); attr.pathname = PTR_TO_UINT64((void *) bpffs_path); attr.bpf_fd = prog_fd; return RET_NERRNO(bpf(BPF_OBJ_PIN, &attr, sizeof(attr))); } int bpf_program_get_id_by_fd(int prog_fd, uint32_t *ret_id) { struct bpf_prog_info info = {}; int r; assert(ret_id); r = bpf_program_get_info_by_fd(prog_fd, &info, sizeof(info)); if (r < 0) return r; *ret_id = info.id; return 0; }; int bpf_program_serialize_attachment( FILE *f, FDSet *fds, const char *key, BPFProgram *p) { _cleanup_free_ char *escaped = NULL; int copy, r; if (!p || !p->attached_path) return 0; assert(p->kernel_fd >= 0); escaped = cescape(p->attached_path); if (!escaped) return -ENOMEM; copy = fdset_put_dup(fds, p->kernel_fd); if (copy < 0) return log_error_errno(copy, "Failed to add BPF kernel fd to serialize: %m"); r = serialize_item_format( f, key, "%i %s %s", copy, bpf_cgroup_attach_type_to_string(p->attached_type), escaped); if (r < 0) return r; /* After serialization, let's forget the fact that this program is attached. The attachment — if you * so will — is now 'owned' by the serialization, and not us anymore. Why does that matter? Because * of BPF's less-than-ideal lifecycle handling: to detach a program from a cgroup we have to * explicitly do so, it's not done implicitly on close(). Now, since we are serializing here we don't * want the program to be detached while freeing things, so that the attachment can be retained after * deserializing again. bpf_program_free() implicitly detaches things, if attached_path is non-NULL, * hence we set it to NULL here. */ p->attached_path = mfree(p->attached_path); return 0; } int bpf_program_serialize_attachment_set(FILE *f, FDSet *fds, const char *key, Set *set) { BPFProgram *p; int r; SET_FOREACH(p, set) { r = bpf_program_serialize_attachment(f, fds, key, p); if (r < 0) return r; } return 0; } int bpf_program_deserialize_attachment(const char *v, FDSet *fds, BPFProgram **bpfp) { _cleanup_free_ char *sfd = NULL, *sat = NULL, *unescaped = NULL; _cleanup_(bpf_program_freep) BPFProgram *p = NULL; _cleanup_close_ int fd = -1; ssize_t l; int ifd, at, r; assert(v); assert(bpfp); /* Extract first word: the fd number */ r = extract_first_word(&v, &sfd, NULL, 0); if (r < 0) return r; if (r == 0) return -EINVAL; r = safe_atoi(sfd, &ifd); if (r < 0) return r; if (ifd < 0) return -EBADF; /* Extract second word: the attach type */ r = extract_first_word(&v, &sat, NULL, 0); if (r < 0) return r; if (r == 0) return -EINVAL; at = bpf_cgroup_attach_type_from_string(sat); if (at < 0) return at; /* The rest is the path */ l = cunescape(v, 0, &unescaped); if (l < 0) return l; fd = fdset_remove(fds, ifd); if (fd < 0) return fd; p = new(BPFProgram, 1); if (!p) return -ENOMEM; *p = (BPFProgram) { .kernel_fd = TAKE_FD(fd), .prog_type = BPF_PROG_TYPE_UNSPEC, .attached_path = TAKE_PTR(unescaped), .attached_type = at, }; if (*bpfp) bpf_program_free(*bpfp); *bpfp = TAKE_PTR(p); return 0; } int bpf_program_deserialize_attachment_set(const char *v, FDSet *fds, Set **bpfsetp) { BPFProgram *p = NULL; int r; assert(v); assert(bpfsetp); r = bpf_program_deserialize_attachment(v, fds, &p); if (r < 0) return r; r = set_ensure_consume(bpfsetp, &bpf_program_hash_ops, p); if (r < 0) return r; return 0; }