From: KP Singh <kpsingh@xxxxxxxxxx>
Add functionality in libbpf to attach eBPF program to LSM hooks.
Signed-off-by: KP Singh <kpsingh@xxxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 127 +++++++++++++++++++++++++++++++++++++--
tools/lib/bpf/libbpf.h | 2 +
tools/lib/bpf/libbpf.map | 1 +
3 files changed, 126 insertions(+), 4 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index b0b27d8e5a37..ab2b23b4f21f 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -5122,8 +5122,8 @@ int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
return -ESRCH;
}
-static inline int __btf__typdef_with_prefix(struct btf *btf, const char *name,
- const char *prefix)
+static inline int __btf__type_with_prefix(struct btf *btf, const char *name,
+ const char *prefix)
{
size_t prefix_len = strlen(prefix);
@@ -5149,9 +5149,9 @@ int libbpf_find_vmlinux_btf_id(const char *name,
}
if (attach_type == BPF_TRACE_RAW_TP)
- err = __btf__typdef_with_prefix(btf, name, BTF_TRACE_PREFIX);
+ err = __btf__type_with_prefix(btf, name, BTF_TRACE_PREFIX);
else if (attach_type == BPF_LSM_MAC)
- err = __btf__typdef_with_prefix(btf, name, BTF_LSM_PREFIX);
+ err = __btf__type_with_prefix(btf, name, BTF_LSM_PREFIX);
else
err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
@@ -5502,6 +5502,18 @@ struct bpf_link_fd {
int fd; /* hook FD */
};
+/*
+ * The other attach types allow the link to be destroyed by using an ioctl or
+ * an operation on some file descriptor that describes the attachment. An LSM
+ * hook can have multiple programs attached to each hook, so the link needs to
+ * specify the program that must be detached when the link is destroyed.
+ */
+struct bpf_link_lsm {
+ struct bpf_link link;
+ int hook_fd;
+ int prog_fd;
+};
+
static int bpf_link__destroy_perf_event(struct bpf_link *link)
{
struct bpf_link_fd *l = (void *)link;
@@ -5876,6 +5888,113 @@ struct bpf_link *bpf_program__attach_trace(struct bpf_program *prog)
return (struct bpf_link *)link;
}
+
+static int bpf_link__destroy_lsm(struct bpf_link *link)
+{
+ struct bpf_link_lsm *ll = container_of(link, struct bpf_link_lsm, link);
+ char errmsg[STRERR_BUFSIZE];
+ int ret;
+
+ ret = bpf_prog_detach2(ll->prog_fd, ll->hook_fd, BPF_LSM_MAC);
+ if (ret < 0) {
+ ret = -errno;
+ pr_warn("failed to detach from hook: %s\n",
+ libbpf_strerror_r(ret, errmsg, sizeof(errmsg)));
+ return ret;
+ }
+ close(ll->hook_fd);
+ return 0;
+}
+
+static const char *__lsm_hook_name(const char *title)
+{
+
+ int i;
+
+ if (!title)
+ return ERR_PTR(-EINVAL);
+
+ for (i = 0; i < ARRAY_SIZE(section_names); i++) {
+ if (section_names[i].prog_type != BPF_PROG_TYPE_LSM)
+ continue;
+
+ if (strncmp(title, section_names[i].sec,
+ section_names[i].len)) {
+ pr_warn("title for a LSM prog must begin with '%s'\n",
+ section_names[i].sec);
+ return ERR_PTR(-EINVAL);
+ }
+
+ return title + section_names[i].len;
+ }
+
+ pr_warn("could not find section information for BPF_PROG_TYPE_LSM\n");
+ return ERR_PTR(-ESRCH);
+}
+
+struct bpf_link *bpf_program__attach_lsm(struct bpf_program *prog)
+{
+ char hook_path[PATH_MAX] = "/sys/kernel/security/bpf/";
+ const char *title, *hook_name;
+ char errmsg[STRERR_BUFSIZE];
+ int prog_fd, target_fd, ret;
+ struct bpf_link_lsm *link;
+
+ title = bpf_program__title(prog, false);
+ if (IS_ERR(title)) {
+ pr_warn("could not determine title of the program\n");
+ return ERR_PTR(-EINVAL);
+ }
+
+ hook_name = __lsm_hook_name(title);
+ if (IS_ERR(hook_name)) {
+ pr_warn("could not determine LSM hook name from title '%s'\n",
+ title);
+ return ERR_PTR(-EINVAL);
+ }
+
+ prog_fd = bpf_program__fd(prog);
+ if (prog_fd < 0) {
+ pr_warn("program '%s': can't attach before loaded\n", title);
+ return ERR_PTR(-EINVAL);
+ }
+
+ link = malloc(sizeof(*link));
+ if (!link)
+ return ERR_PTR(-ENOMEM);
+ link->link.destroy = &bpf_link__destroy_lsm;
+
+ /* Attach the BPF program to the given hook */
+ strncat(hook_path, hook_name,
+ sizeof(hook_path) - (strlen(hook_path) + 1));
+ target_fd = open(hook_path, O_RDWR);
+ if (target_fd < 0) {
+ ret = -errno;
+ pr_warn("program '%s': failed to open to hook '%s': %s\n",
+ title, hook_path,
+ libbpf_strerror_r(ret, errmsg, sizeof(errmsg)));
+ return ERR_PTR(ret);
+ }
+
+ ret = bpf_prog_attach(prog_fd, target_fd, BPF_LSM_MAC,
+ BPF_F_ALLOW_OVERRIDE);
+ if (ret < 0) {
+ ret = -errno;
+ pr_warn("program '%s': failed to attach to hook '%s': %s\n",
+ title, hook_name,
+ libbpf_strerror_r(ret, errmsg, sizeof(errmsg)));
+ goto error;
+ }
+
+ link->hook_fd = target_fd;
+ link->prog_fd = prog_fd;
+ return &link->link;
+
+error:
+ close(target_fd);
+ return ERR_PTR(ret);
+}
+
enum bpf_perf_event_ret
bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
void **copy_mem, size_t *copy_size,
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 9cd69d602c82..655f27ad6ece 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -256,6 +256,8 @@ 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_insn;
/*
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 3d396149755d..5d64ba9b2a43 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -213,4 +213,5 @@ LIBBPF_0.0.7 {
global:
bpf_program__is_lsm;
bpf_program__set_lsm;
+ bpf_program__attach_lsm;
} LIBBPF_0.0.6;
--
2.20.1
