bpf: lsm: Provide attachment points for BPF LSM programs

When CONFIG_BPF_LSM is enabled, nop functions, bpf_lsm_<hook_name>, are
generated for each LSM hook. These functions are initialized as LSM
hooks in a subsequent patch.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: James Morris <jamorris@linux.microsoft.com>
Link: https://lore.kernel.org/bpf/20200329004356.27286-4-kpsingh@chromium.org

1 files changed, 14 insertions, 0 deletions

diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 82875039ca90..3b3bbb28603e 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -7,6 +7,20 @@
 #include <linux/filter.h>
 #include <linux/bpf.h>
 #include <linux/btf.h>
+#include <linux/lsm_hooks.h>
+#include <linux/bpf_lsm.h>
+
+/* For every LSM hook that allows attachment of BPF programs, declare a nop
+ * function where a BPF program can be attached.
+ */
+#define LSM_HOOK(RET, DEFAULT, NAME, ...)	\
+noinline RET bpf_lsm_##NAME(__VA_ARGS__)	\
+{						\
+	return DEFAULT;				\
+}
+
+#include <linux/lsm_hook_defs.h>
+#undef LSM_HOOK
 
 const struct bpf_prog_ops lsm_prog_ops = {
 };