bpf: remove bpf_key reference

bpf_key.has_ref is used to distinguish between real key pointers and
the fake key pointers that are used for system keyrings (to ensure the
actual pointers to system keyrings are never visible outside
certs/system_keyring.c).  The keyrings subsystem has an exported
function to do this, so use that in the bpf keyring code eliminating
the need to store has_ref.

Signed-off-by: James Bottomley <[email protected]>

Author: jejb

kernel/trace/bpf_trace.c

@@ -1244,7 +1244,6 @@ static const struct bpf_func_proto bpf_get_func_arg_cnt_proto = {
 #ifdef CONFIG_KEYS
 struct bpf_key {
 	struct key *key;
-	bool has_ref;
 };
 
 __bpf_kfunc_start_defs();
@@ -1297,7 +1296,6 @@ __bpf_kfunc struct bpf_key *bpf_lookup_user_key(s32 serial, u64 flags)
 	}
 
 	bkey->key = key_ref_to_ptr(key_ref);
-	bkey->has_ref = true;
 
 	return bkey;
 }
@@ -1335,7 +1333,6 @@ __bpf_kfunc struct bpf_key *bpf_lookup_system_key(u64 id)
 		return NULL;
 
 	bkey->key = (struct key *)(unsigned long)id;
-	bkey->has_ref = false;
 
 	return bkey;
 }
@@ -1349,7 +1346,7 @@ __bpf_kfunc struct bpf_key *bpf_lookup_system_key(u64 id)
  */
 __bpf_kfunc void bpf_key_put(struct bpf_key *bkey)
 {
-	if (bkey->has_ref)
+	if (system_keyring_id_check((unsigned long)bkey->key) < 0)
 		key_put(bkey->key);
 
 	kfree(bkey);
@@ -1377,7 +1374,7 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_p,
 	u32 data_len, sig_len;
 	int ret;
 
-	if (trusted_keyring->has_ref) {
+	if (system_keyring_id_check((unsigned long)trusted_keyring->key) < 0) {
 		/*
 		 * Do the permission check deferred in bpf_lookup_user_key().
 		 * See bpf_lookup_user_key() for more details.