[RFC 1/2] ima: Add kernel parameter to disable IMA

[Song Liu]

This patch provides kernel parameter 'ima=off' that disables IMA.
This will reduce memory consumption by the ima when it is not needed.
Specifically, this saves one pointer per inode in the system.

Originally-by: Dmitry Kasatkin <dmitry.kasatkin@xxxxxxxxx>
Signed-off-by: Song Liu <song@xxxxxxxxxx>
---
 security/integrity/ima/ima_main.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 06132cf47016..21968c78f03f 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -1144,10 +1144,22 @@ static int ima_kernel_module_request(char *kmod_name)
 
 #endif /* CONFIG_INTEGRITY_ASYMMETRIC_KEYS */
 
+
+static int ima_mode = 1;
+static int __init ima_setup(char *str)
+{
+	if (strncmp(str, "off", 3) == 0)
+		ima_mode = 0;
+	return 1;
+}
+__setup("ima=", ima_setup);
+
 static int __init init_ima(void)
 {
 	int error;
 
+	if (!ima_mode)
+		return 0;
 	ima_appraise_parse_cmdline();
 	ima_init_template_list();
 	hash_setup(CONFIG_IMA_DEFAULT_HASH);
@@ -1217,6 +1229,7 @@ DEFINE_LSM(ima) = {
 	.name = "ima",
 	.init = init_ima_lsm,
 	.order = LSM_ORDER_LAST,
+	.enabled = &ima_mode,
 	.blobs = &ima_blob_sizes,
 };
 
-- 
2.43.5