[PATCH bpf-next 10/13] bpf: invoke security_bpf_prog_load_post_integrity from the metadata kfunc

[KP Singh]

Call security_bpf_prog_load_post_integrity from
bpf_loader_verify_metadata just before promoting
prog->aux->sig.verdict from BPF_SIG_OK to BPF_SIG_METADATA_VERIFIED.
This lets policy LSMs deny the metadata-verified transition.

A non-zero return aborts the kfunc and leaves the verdict at
BPF_SIG_OK; observers that key off METADATA_VERIFIED never see a
verdict the LSM denied.

Signed-off-by: KP Singh <kpsingh at kernel.org>
---
 kernel/bpf/helpers.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 9afa71fbcac3..52e71fb6e200 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -4300,6 +4300,14 @@ __bpf_kfunc int bpf_loader_verify_metadata(struct bpf_map *map,
 	if (memcmp(sha, hash, SHA256_DIGEST_SIZE))
 		return -EBADMSG;
 
+	/* Metadata integrity is decided by the checks above; the LSM hook
+	 * is an observer of that verdict and may apply policy (e.g. deny),
+	 * but cannot vouch for integrity it did not verify itself.
+	 */
+	err = security_bpf_prog_load_post_integrity(aux__ign->prog);
+	if (err)
+		return err;
+
 	aux__ign->sig.verdict = BPF_SIG_METADATA_VERIFIED;
 	return 0;
 }
-- 
2.53.0