[PATCH bpf-next 09/13] lsm: add bpf_prog_load_post_integrity hook

[KP Singh]

Add a companion to security_bpf_prog_load. The existing hook fires
at PROG_LOAD entry where the verdict is at most BPF_SIG_OK; the new
hook fires from bpf_loader_verify_metadata after the in-kernel
metadata check, just before sig.verdict is promoted to
BPF_SIG_METADATA_VERIFIED. Policy LSMs that want to gate on
metadata verification (not just signature presence) register here.

Signed-off-by: KP Singh <kpsingh at kernel.org>
---
 include/linux/lsm_hook_defs.h |  1 +
 include/linux/security.h      |  6 ++++++
 security/security.c           | 17 +++++++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 2b8dfb35caed..c0e7899756d4 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -446,6 +446,7 @@ LSM_HOOK(int, 0, bpf_map_create, struct bpf_map *map, union bpf_attr *attr,
 LSM_HOOK(void, LSM_RET_VOID, bpf_map_free, struct bpf_map *map)
 LSM_HOOK(int, 0, bpf_prog_load, struct bpf_prog *prog, union bpf_attr *attr,
 	 struct bpf_token *token, bool kernel)
+LSM_HOOK(int, 0, bpf_prog_load_post_integrity, struct bpf_prog *prog)
 LSM_HOOK(void, LSM_RET_VOID, bpf_prog_free, struct bpf_prog *prog)
 LSM_HOOK(int, 0, bpf_token_create, struct bpf_token *token, union bpf_attr *attr,
 	 const struct path *path)
diff --git a/include/linux/security.h b/include/linux/security.h
index 41d7367cf403..3a8f2c50f7be 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -2305,6 +2305,7 @@ extern int security_bpf_map_create(struct bpf_map *map, union bpf_attr *attr,
 extern void security_bpf_map_free(struct bpf_map *map);
 extern int security_bpf_prog_load(struct bpf_prog *prog, union bpf_attr *attr,
 				  struct bpf_token *token, bool kernel);
+extern int security_bpf_prog_load_post_integrity(struct bpf_prog *prog);
 extern void security_bpf_prog_free(struct bpf_prog *prog);
 extern int security_bpf_token_create(struct bpf_token *token, union bpf_attr *attr,
 				     const struct path *path);
@@ -2343,6 +2344,11 @@ static inline int security_bpf_prog_load(struct bpf_prog *prog, union bpf_attr *
 	return 0;
 }
 
+static inline int security_bpf_prog_load_post_integrity(struct bpf_prog *prog)
+{
+	return 0;
+}
+
 static inline void security_bpf_prog_free(struct bpf_prog *prog)
 { }
 
diff --git a/security/security.c b/security/security.c
index 4e999f023651..05153e8496c9 100644
--- a/security/security.c
+++ b/security/security.c
@@ -5383,6 +5383,23 @@ int security_bpf_prog_load(struct bpf_prog *prog, union bpf_attr *attr,
 	return rc;
 }
 
+/**
+ * security_bpf_prog_load_post_integrity() - Notify LSMs that a signed loader
+ * has just verified its metadata map.
+ * @prog: the loader BPF program whose metadata check passed.
+ *
+ * Invoked by bpf_loader_verify_metadata() after the kernel-side hash check
+ * succeeds, before prog->aux->sig_verdict is promoted to
+ * BPF_SIG_METADATA_VERIFIED. A non-zero return aborts the kfunc and leaves
+ * the verdict at BPF_SIG_OK.
+ *
+ * Return: 0 on success, negative errno to deny.
+ */
+int security_bpf_prog_load_post_integrity(struct bpf_prog *prog)
+{
+	return call_int_hook(bpf_prog_load_post_integrity, prog);
+}
+
 /**
  * security_bpf_token_create() - Check if creating of BPF token is allowed
  * @token: BPF token object
-- 
2.53.0