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Subject[PATCH bpf-next v2 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_index

Signed-off-by: KP Singh <kpsingh@google.com>
---
tools/lib/bpf/bpf.c | 6 +-
tools/lib/bpf/bpf.h | 1 +
tools/lib/bpf/libbpf.c | 143 ++++++++++++++++++++++++++++++++++-----
tools/lib/bpf/libbpf.h | 4 ++
tools/lib/bpf/libbpf.map | 3 +
5 files changed, 138 insertions(+), 19 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 500afe478e94..b138d98ff862 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_index = load_attr->lsm_hook_index;
+ } 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.attach_btf_id = load_attr->attach_btf_id;
@@ -244,6 +247,7 @@ 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 56341d117e5b..54458a102939 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -86,6 +86,7 @@ struct bpf_load_program_attr {
__u32 prog_ifindex;
__u32 attach_btf_id;
};
+ __u32 lsm_hook_index;
__u32 prog_btf_fd;
__u32 func_info_rec_size;
const void *func_info;
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 0c229f00a67e..60737559a9a6 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -229,6 +229,7 @@ struct bpf_program {
enum bpf_attach_type expected_attach_type;
__u32 attach_btf_id;
__u32 attach_prog_fd;
+ __u32 lsm_hook_index;
void *func_info;
__u32 func_info_rec_size;
__u32 func_info_cnt;
@@ -4886,7 +4887,10 @@ 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_index = prog->lsm_hook_index;
+ } 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) {
load_attr.attach_prog_fd = prog->attach_prog_fd;
@@ -4895,6 +4899,7 @@ 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);
@@ -4967,9 +4972,11 @@ static int libbpf_find_attach_btf_id(const char *name,
enum bpf_attach_type attach_type,
__u32 attach_prog_fd);

+static __s32 btf__find_lsm_hook_index(const char *name);
+
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, index;

if (prog->type == BPF_PROG_TYPE_TRACING) {
btf_id = libbpf_find_attach_btf_id(prog->section_name,
@@ -4980,6 +4987,13 @@ 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) {
+ index = btf__find_lsm_hook_index(prog->section_name);
+ if (index < 0)
+ return index;
+ prog->lsm_hook_index = index;
+ }
+
if (prog->instances.nr < 0 || !prog->instances.fds) {
if (prog->preprocessor) {
pr_warn("Internal error: can't load program '%s'\n",
@@ -6207,6 +6221,7 @@ 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);
@@ -6272,6 +6287,8 @@ 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;
@@ -6315,12 +6332,17 @@ static const struct bpf_sec_def section_defs[] = {
.expected_attach_type = BPF_TRACE_FEXIT,
.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),
BPF_PROG_SEC("lwt_out", BPF_PROG_TYPE_LWT_OUT),
BPF_PROG_SEC("lwt_xmit", BPF_PROG_TYPE_LWT_XMIT),
BPF_PROG_SEC("lwt_seg6local", BPF_PROG_TYPE_LWT_SEG6LOCAL),
+ BPF_PROG_BTF("lsm/", BPF_PROG_TYPE_LSM,
+ BPF_LSM_MAC),
BPF_APROG_SEC("cgroup_skb/ingress", BPF_PROG_TYPE_CGROUP_SKB,
BPF_CGROUP_INET_INGRESS),
BPF_APROG_SEC("cgroup_skb/egress", BPF_PROG_TYPE_CGROUP_SKB,
@@ -6576,32 +6598,80 @@ static int bpf_object__collect_struct_ops_map_reloc(struct bpf_object *obj,
return -EINVAL;
}

-#define BTF_PREFIX "btf_trace_"
+#define BTF_TRACE_PREFIX "btf_trace_"
+
+static inline int btf__find_by_prefix_kind(struct btf *btf, const char *name,
+ const char *prefix, __u32 kind)
+{
+ char btf_type_name[128];
+
+ snprintf(btf_type_name, sizeof(btf_type_name), "%s%s", prefix, name);
+ return btf__find_by_name_kind(btf, btf_type_name, kind);
+}
+
+static __s32 btf__find_lsm_hook_index(const char *name)
+{
+ struct btf *btf = bpf_find_kernel_btf();
+ const struct bpf_sec_def *sec_def;
+ const struct btf_type *hl_type;
+ struct btf_member *m;
+ __u16 vlen;
+ __s32 hl_id;
+ int j;
+
+ sec_def = find_sec_def(name);
+ if (!sec_def)
+ return -ESRCH;
+
+ name += sec_def->len;
+
+ hl_id = btf__find_by_name_kind(btf, "security_hook_heads",
+ BTF_KIND_STRUCT);
+ if (hl_id < 0) {
+ pr_debug("security_hook_heads cannot be found in BTF\n");
+ return hl_id;
+ }
+
+ hl_type = btf__type_by_id(btf, hl_id);
+ if (!hl_type) {
+ pr_warn("Can't find type for security_hook_heads: %u\n", hl_id);
+ return -EINVAL;
+ }
+
+ m = btf_members(hl_type);
+ vlen = btf_vlen(hl_type);
+
+ for (j = 0; j < vlen; j++) {
+ if (!strcmp(btf__name_by_offset(btf, m->name_off), name))
+ return j + 1;
+ m++;
+ }
+
+ pr_warn("Cannot find offset for %s in security_hook_heads\n", name);
+ return -ENOENT;
+}
+
int libbpf_find_vmlinux_btf_id(const char *name,
enum bpf_attach_type attach_type)
{
struct btf *btf = bpf_find_kernel_btf();
- char raw_tp_btf[128] = BTF_PREFIX;
- char *dst = raw_tp_btf + sizeof(BTF_PREFIX) - 1;
- const char *btf_name;
int err = -EINVAL;
- __u32 kind;

if (IS_ERR(btf)) {
pr_warn("vmlinux BTF is not found\n");
return -EINVAL;
}

- if (attach_type == BPF_TRACE_RAW_TP) {
- /* prepend "btf_trace_" prefix per kernel convention */
- strncat(dst, name, sizeof(raw_tp_btf) - sizeof(BTF_PREFIX));
- btf_name = raw_tp_btf;
- kind = BTF_KIND_TYPEDEF;
- } else {
- btf_name = name;
- kind = BTF_KIND_FUNC;
- }
- err = btf__find_by_name_kind(btf, btf_name, kind);
+ if (attach_type == BPF_TRACE_RAW_TP)
+ err = btf__find_by_prefix_kind(btf, name, BTF_TRACE_PREFIX,
+ BTF_KIND_TYPEDEF);
+ else
+ err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
+
+ /* err = 0 means void / UNKNOWN which is treated as an error */
+ if (err == 0)
+ err = -EINVAL;
+
btf__free(btf);
return err;
}
@@ -6630,7 +6700,7 @@ static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd)
}
err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
btf__free(btf);
- if (err <= 0) {
+ if (err < 0) {
pr_warn("%s is not found in prog's BTF\n", name);
goto out;
}
@@ -7395,6 +7465,43 @@ 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,
+ BPF_F_ALLOW_OVERRIDE);
+ if (pfd < 0) {
+ pfd = -errno;
+ 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 01639f9a1062..a97e709a29e6 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -241,6 +241,8 @@ LIBBPF_API struct bpf_link *
bpf_program__attach_trace(struct bpf_program *prog);
struct bpf_map;
LIBBPF_API struct bpf_link *bpf_map__attach_struct_ops(struct bpf_map *map);
+LIBBPF_API struct bpf_link *
+bpf_program__attach_lsm(struct bpf_program *prog);
struct bpf_insn;

/*
@@ -318,6 +320,7 @@ LIBBPF_API int bpf_program__set_xdp(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_perf_event(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_tracing(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_struct_ops(struct bpf_program *prog);
+LIBBPF_API int bpf_program__set_lsm(struct bpf_program *prog);

LIBBPF_API enum bpf_prog_type bpf_program__get_type(struct bpf_program *prog);
LIBBPF_API void bpf_program__set_type(struct bpf_program *prog,
@@ -339,6 +342,7 @@ LIBBPF_API bool bpf_program__is_xdp(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_perf_event(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_tracing(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_struct_ops(const struct bpf_program *prog);
+LIBBPF_API bool bpf_program__is_lsm(const struct bpf_program *prog);

/*
* No need for __attribute__((packed)), all members of 'bpf_map_def'
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index a19f04e6e3d9..3da0452ce679 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -227,4 +227,7 @@ LIBBPF_0.0.7 {
bpf_program__is_struct_ops;
bpf_program__set_struct_ops;
btf__align_of;
+ bpf_program__is_lsm;
+ bpf_program__set_lsm;
+ bpf_program__attach_lsm;
} LIBBPF_0.0.6;
--
2.20.1
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