[PATCH v2 2/3] evm: Don't enable fix mode when secure boot is enabled

[Coiby Xu]

Similar to IMA fix mode, forbid EVM fix mode when secure boot is
enabled.

Reported-and-suggested-by: Mimi Zohar <zohar at linux.ibm.com>
Suggested-by: Roberto Sassu <roberto.sassu at huawei.com>
Signed-off-by: Coiby Xu <coxu at redhat.com>
---
 security/integrity/evm/evm_main.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 73d500a375cb..a54cb73b51ee 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -72,17 +72,25 @@ static struct xattr_list evm_config_default_xattrnames[] = {
 
 LIST_HEAD(evm_config_xattrnames);
 
+static char *evm_cmdline __initdata;
+core_param(evm, evm_cmdline, charp, 0);
+
 static int evm_fixmode __ro_after_init;
-static int __init evm_set_fixmode(char *str)
+static void __init evm_set_fixmode(void)
 {
-	if (strncmp(str, "fix", 3) == 0)
-		evm_fixmode = 1;
-	else
-		pr_err("invalid \"%s\" mode", str);
+	if (!evm_cmdline)
+		return;
 
-	return 1;
+	if (strncmp(evm_cmdline, "fix", 3) == 0) {
+		if (arch_get_secureboot()) {
+			pr_info("Secure boot enabled: ignoring evm=fix");
+			return;
+		}
+		evm_fixmode = 1;
+	} else {
+		pr_err("invalid \"%s\" mode", evm_cmdline);
+	}
 }
-__setup("evm=", evm_set_fixmode);
 
 static void __init evm_init_config(void)
 {
@@ -1119,6 +1127,8 @@ static int __init init_evm(void)
 
 	evm_init_config();
 
+	evm_set_fixmode();
+
 	error = integrity_init_keyring(INTEGRITY_KEYRING_EVM);
 	if (error)
 		goto error;
-- 
2.52.0