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Subject[PATCH bpf-next v3 08/10] tools/libbpf: Add support for BPF_PROG_TYPE_LSM
Date
From: KP Singh <kpsingh@google.com>

* Add functionality in libbpf to attach eBPF program to LSM hooks
* Lookup the index of the LSM hook in security_hook_heads and pass it in
attr->lsm_hook_idx

Signed-off-by: KP Singh <kpsingh@google.com>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Reviewed-by: Thomas Garnier <thgarnie@google.com>
---
tools/lib/bpf/bpf.c | 6 ++-
tools/lib/bpf/bpf.h | 1 +
tools/lib/bpf/libbpf.c | 104 +++++++++++++++++++++++++++++++++++++--
tools/lib/bpf/libbpf.h | 4 ++
tools/lib/bpf/libbpf.map | 3 ++
5 files changed, 114 insertions(+), 4 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index c6dafe563176..60dac1b80e5a 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -235,7 +235,10 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
memset(&attr, 0, sizeof(attr));
attr.prog_type = load_attr->prog_type;
attr.expected_attach_type = load_attr->expected_attach_type;
- if (attr.prog_type == BPF_PROG_TYPE_STRUCT_OPS) {
+
+ if (attr.prog_type == BPF_PROG_TYPE_LSM) {
+ attr.lsm_hook_idx = load_attr->lsm_hook_idx;
+ } else if (attr.prog_type == BPF_PROG_TYPE_STRUCT_OPS) {
attr.attach_btf_id = load_attr->attach_btf_id;
} else if (attr.prog_type == BPF_PROG_TYPE_TRACING ||
attr.prog_type == BPF_PROG_TYPE_EXT) {
@@ -245,6 +248,7 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
attr.prog_ifindex = load_attr->prog_ifindex;
attr.kern_version = load_attr->kern_version;
}
+
attr.insn_cnt = (__u32)load_attr->insns_cnt;
attr.insns = ptr_to_u64(load_attr->insns);
attr.license = ptr_to_u64(load_attr->license);
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index b976e77316cc..cfd59f7c29a7 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -85,6 +85,7 @@ struct bpf_load_program_attr {
union {
__u32 prog_ifindex;
__u32 attach_btf_id;
+ __u32 lsm_hook_idx;
};
__u32 prog_btf_fd;
__u32 func_info_rec_size;
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ae34b681ae82..1ecbf6c78b97 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -228,6 +228,7 @@ struct bpf_program {
enum bpf_attach_type expected_attach_type;
__u32 attach_btf_id;
__u32 attach_prog_fd;
+ __u32 lsm_hook_idx;
void *func_info;
__u32 func_info_rec_size;
__u32 func_info_cnt;
@@ -2352,7 +2353,9 @@ static int bpf_object__finalize_btf(struct bpf_object *obj)

static inline bool libbpf_prog_needs_vmlinux_btf(struct bpf_program *prog)
{
- if (prog->type == BPF_PROG_TYPE_STRUCT_OPS)
+
+ if (prog->type == BPF_PROG_TYPE_LSM ||
+ prog->type == BPF_PROG_TYPE_STRUCT_OPS)
return true;

/* BPF_PROG_TYPE_TRACING programs which do not attach to other programs
@@ -4835,7 +4838,10 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
load_attr.insns = insns;
load_attr.insns_cnt = insns_cnt;
load_attr.license = license;
- if (prog->type == BPF_PROG_TYPE_STRUCT_OPS) {
+
+ if (prog->type == BPF_PROG_TYPE_LSM) {
+ load_attr.lsm_hook_idx = prog->lsm_hook_idx;
+ } else if (prog->type == BPF_PROG_TYPE_STRUCT_OPS) {
load_attr.attach_btf_id = prog->attach_btf_id;
} else if (prog->type == BPF_PROG_TYPE_TRACING ||
prog->type == BPF_PROG_TYPE_EXT) {
@@ -4845,6 +4851,7 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
load_attr.kern_version = kern_version;
load_attr.prog_ifindex = prog->prog_ifindex;
}
+
/* if .BTF.ext was loaded, kernel supports associated BTF for prog */
if (prog->obj->btf_ext)
btf_fd = bpf_object__btf_fd(prog->obj);
@@ -4914,10 +4921,11 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
}

static int libbpf_find_attach_btf_id(struct bpf_program *prog);
+static __s32 find_lsm_hook_idx(struct bpf_program *prog);

int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver)
{
- int err = 0, fd, i, btf_id;
+ int err = 0, fd, i, btf_id, idx;

if (prog->type == BPF_PROG_TYPE_TRACING ||
prog->type == BPF_PROG_TYPE_EXT) {
@@ -4927,6 +4935,13 @@ int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver)
prog->attach_btf_id = btf_id;
}

+ if (prog->type == BPF_PROG_TYPE_LSM) {
+ idx = find_lsm_hook_idx(prog);
+ if (idx < 0)
+ return idx;
+ prog->lsm_hook_idx = idx;
+ }
+
if (prog->instances.nr < 0 || !prog->instances.fds) {
if (prog->preprocessor) {
pr_warn("Internal error: can't load program '%s'\n",
@@ -5084,6 +5099,8 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
if (prog->type != BPF_PROG_TYPE_UNSPEC)
continue;

+
+
err = libbpf_prog_type_by_name(prog->section_name, &prog_type,
&attach_type);
if (err == -ESRCH)
@@ -6160,6 +6177,7 @@ bool bpf_program__is_##NAME(const struct bpf_program *prog) \
} \

BPF_PROG_TYPE_FNS(socket_filter, BPF_PROG_TYPE_SOCKET_FILTER);
+BPF_PROG_TYPE_FNS(lsm, BPF_PROG_TYPE_LSM);
BPF_PROG_TYPE_FNS(kprobe, BPF_PROG_TYPE_KPROBE);
BPF_PROG_TYPE_FNS(sched_cls, BPF_PROG_TYPE_SCHED_CLS);
BPF_PROG_TYPE_FNS(sched_act, BPF_PROG_TYPE_SCHED_ACT);
@@ -6226,6 +6244,8 @@ static struct bpf_link *attach_raw_tp(const struct bpf_sec_def *sec,
struct bpf_program *prog);
static struct bpf_link *attach_trace(const struct bpf_sec_def *sec,
struct bpf_program *prog);
+static struct bpf_link *attach_lsm(const struct bpf_sec_def *sec,
+ struct bpf_program *prog);

struct bpf_sec_def {
const char *sec;
@@ -6272,6 +6292,9 @@ static const struct bpf_sec_def section_defs[] = {
SEC_DEF("freplace/", EXT,
.is_attach_btf = true,
.attach_fn = attach_trace),
+ SEC_DEF("lsm/", LSM,
+ .expected_attach_type = BPF_LSM_MAC,
+ .attach_fn = attach_lsm),
BPF_PROG_SEC("xdp", BPF_PROG_TYPE_XDP),
BPF_PROG_SEC("perf_event", BPF_PROG_TYPE_PERF_EVENT),
BPF_PROG_SEC("lwt_in", BPF_PROG_TYPE_LWT_IN),
@@ -6533,6 +6556,44 @@ static int bpf_object__collect_struct_ops_map_reloc(struct bpf_object *obj,
return -EINVAL;
}

+static __s32 find_lsm_hook_idx(struct bpf_program *prog)
+{
+ struct btf *btf = prog->obj->btf_vmlinux;
+ const char *name = prog->section_name;
+ const struct bpf_sec_def *sec_def;
+ const struct btf_type *t;
+ struct btf_member *m;
+ __s32 type_id;
+ int i;
+
+ sec_def = find_sec_def(name);
+ if (!sec_def)
+ return -ESRCH;
+
+ name += sec_def->len;
+
+ type_id = btf__find_by_name_kind(btf, "security_hook_heads",
+ BTF_KIND_STRUCT);
+ if (type_id < 0) {
+ pr_warn("security_hook_heads not found in vmlinux BTF\n");
+ return type_id;
+ }
+
+ t = btf__type_by_id(btf, type_id);
+ if (!t) {
+ pr_warn("Can't find type for security_hook_heads: %u\n", type_id);
+ return -ESRCH;
+ }
+
+ for (m = btf_members(t), i = 0; i < btf_vlen(t); i++, m++) {
+ if (!strcmp(btf__name_by_offset(btf, m->name_off), name))
+ return i;
+ }
+
+ pr_warn("Can't find lsm_hook_idx for %s in security_hook_heads\n", name);
+ return -ESRCH;
+}
+
#define BTF_TRACE_PREFIX "btf_trace_"
#define BTF_MAX_NAME_SIZE 128

@@ -7372,6 +7433,43 @@ static struct bpf_link *attach_trace(const struct bpf_sec_def *sec,
return bpf_program__attach_trace(prog);
}

+struct bpf_link *bpf_program__attach_lsm(struct bpf_program *prog)
+{
+ char errmsg[STRERR_BUFSIZE];
+ struct bpf_link_fd *link;
+ int prog_fd, pfd;
+
+ prog_fd = bpf_program__fd(prog);
+ if (prog_fd < 0) {
+ pr_warn("program '%s': can't attach before loaded\n",
+ bpf_program__title(prog, false));
+ return ERR_PTR(-EINVAL);
+ }
+
+ link = calloc(1, sizeof(*link));
+ if (!link)
+ return ERR_PTR(-ENOMEM);
+ link->link.detach = &bpf_link__detach_fd;
+
+ pfd = bpf_prog_attach(prog_fd, 0, BPF_LSM_MAC, 0);
+ if (pfd < 0) {
+ pfd = -errno;
+ free(link);
+ pr_warn("program '%s': failed to attach: %s\n",
+ bpf_program__title(prog, false),
+ libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
+ return ERR_PTR(pfd);
+ }
+ link->fd = pfd;
+ return (struct bpf_link *)link;
+}
+
+static struct bpf_link *attach_lsm(const struct bpf_sec_def *sec,
+ struct bpf_program *prog)
+{
+ return bpf_program__attach_lsm(prog);
+}
+
struct bpf_link *bpf_program__attach(struct bpf_program *prog)
{
const struct bpf_sec_def *sec_def;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 2a5e3b087002..ef09ca980758 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -239,6 +239,8 @@ bpf_program__attach_raw_tracepoint(struct bpf_program *prog,

LIBBPF_API struct bpf_link *
bpf_program__attach_trace(struct bpf_program *prog);
+LIBBPF_API struct bpf_link *
+bpf_program__attach_lsm(struct bpf_program *prog);
struct bpf_map;
LIBBPF_API struct bpf_link *bpf_map__attach_struct_ops(struct bpf_map *map);
struct bpf_insn;
@@ -312,6 +314,7 @@ LIBBPF_API int bpf_program__set_socket_filter(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_tracepoint(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_raw_tracepoint(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_kprobe(struct bpf_program *prog);
+LIBBPF_API int bpf_program__set_lsm(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_sched_cls(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_sched_act(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_xdp(struct bpf_program *prog);
@@ -334,6 +337,7 @@ LIBBPF_API bool bpf_program__is_socket_filter(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_tracepoint(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_raw_tracepoint(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_kprobe(const struct bpf_program *prog);
+LIBBPF_API bool bpf_program__is_lsm(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_sched_cls(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_sched_act(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_xdp(const struct bpf_program *prog);
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index b035122142bb..8df332a528a0 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -227,10 +227,13 @@ LIBBPF_0.0.7 {
bpf_probe_large_insn_limit;
bpf_prog_attach_xattr;
bpf_program__attach;
+ bpf_program__attach_lsm;
bpf_program__name;
bpf_program__is_extension;
+ bpf_program__is_lsm;
bpf_program__is_struct_ops;
bpf_program__set_extension;
+ bpf_program__set_lsm;
bpf_program__set_struct_ops;
btf__align_of;
libbpf_find_kernel_btf;
--
2.20.1
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