modsign: use all trusted keys to verify module signature

Make mod_verify_sig to use all trusted keys. This allows keys in
secondary_trusted_keys to be used to verify PKCS#7 signature on a
kernel module.
Signed-off-by: Ke Wu <mikewu@google.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>

kernel/module_signing.c

@@ -83,6 +83,7 @@ int mod_verify_sig(const void *mod, struct load_info *info)
 	}
 
 	return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
-				      NULL, VERIFYING_MODULE_SIGNATURE,
+				      VERIFY_USE_SECONDARY_KEYRING,
+				      VERIFYING_MODULE_SIGNATURE,
 				      NULL, NULL);
 }