4 files changed, 9 insertions, 4 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index bdb193afe176..90c12c591168 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -569,7 +569,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
         ca_keys=        [KEYS] This parameter identifies a specific key(s) on
                         the system trusted keyring to be used for certificate
                         trust validation.
-                        format: id:<keyid>
+                        format: { id:<keyid> | builtin }
 
         ccw_timeout_log [S390]
                         See Documentation/s390/CommonIO for details.
diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
index d376195e1d08..927ce755ff67 100644
--- a/crypto/asymmetric_keys/x509_public_key.c
+++ b/crypto/asymmetric_keys/x509_public_key.c
@@ -24,6 +24,7 @@
 #include "public_key.h"
 #include "x509_parser.h"
 
+static bool use_builtin_keys;
 static char *ca_keyid;
 
 #ifndef MODULE
@@ -34,6 +35,8 @@ static int __init ca_keys_setup(char *str)
 
         if (strncmp(str, "id:", 3) == 0)
                 ca_keyid = str; /* owner key 'id:xxxxxx' */
+        else if (strcmp(str, "builtin") == 0)
+                use_builtin_keys = true;
 
         return 1;
 }
@@ -180,7 +183,6 @@ EXPORT_SYMBOL_GPL(x509_check_signature);
 static int x509_validate_trust(struct x509_certificate *cert,
                                struct key *trust_keyring)
 {
-        const struct public_key *pk;
         struct key *key;
         int ret = 1;
 
@@ -195,8 +197,9 @@ static int x509_validate_trust(struct x509_certificate *cert,
                                           cert->authority,
                                           strlen(cert->authority));
         if (!IS_ERR(key))  {
-                pk = key->payload.data;
-                ret = x509_check_signature(pk, cert);
+                if (!use_builtin_keys
+                    || test_bit(KEY_FLAG_BUILTIN, &key->flags))
+                        ret = x509_check_signature(key->payload.data, cert);
                 key_put(key);
         }
         return ret;
diff --git a/include/linux/key.h b/include/linux/key.h
index 017b0826642f..65316f7ae794 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -170,6 +170,7 @@ struct key {
 #define KEY_FLAG_INVALIDATED    7       /* set if key has been invalidated */
 #define KEY_FLAG_TRUSTED        8       /* set if key is trusted */
 #define KEY_FLAG_TRUSTED_ONLY   9       /* set if keyring only accepts links to trusted keys */
+#define KEY_FLAG_BUILTIN        10      /* set if key is builtin */
 
         /* the key type and key description string
          * - the desc is used to match a key against search criteria
diff --git a/kernel/system_keyring.c b/kernel/system_keyring.c
index 52ebc70263f4..875f64e8935b 100644
--- a/kernel/system_keyring.c
+++ b/kernel/system_keyring.c
@@ -89,6 +89,7 @@ static __init int load_system_certificate_list(void)
                         pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
                                PTR_ERR(key));
                 } else {
+                        set_bit(KEY_FLAG_BUILTIN, &key_ref_to_ptr(key)->flags);
                         pr_notice("Loaded X.509 cert '%s'\n",
                                   key_ref_to_ptr(key)->description);
                         key_ref_put(key);