[PATCH] allow disabling IMA at runtime

[Kyle McMartin <kyle@mcmartin.ca>]

From: Kyle McMartin <kyle@redhat.com>

Due to a memory leak in IMA that we're currently debugging in Fedora
rawhide, it would be nice to be able to disable that support at runtime.
Currently it's only able to be built in, and there's no toggle to avoid
initializing it.

Provide one, in order to enhance debuggability. If a user can reboot a
machine and edit its command line, one can do a far sight worse things
than disabling a security precaution.

Signed-off-by: Kyle McMartin <kyle@redhat.com>

---
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7936b80..0d1b1ed 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -926,6 +926,11 @@ and is between 256 and 4096 characters. It is defined in the file
 	ihash_entries=	[KNL]
 			Set number of hash buckets for inode cache.
 
+	ima=		[IMA]
+			Format: { "0" | "1" }
+			0 -- disable IMA.
+			1 -- enable IMA. (default)
+
 	ima_audit=	[IMA]
 			Format: { "0" | "1" }
 			0 -- integrity auditing messages. (Default)
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 101c512..cc7603e 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -339,10 +339,27 @@ int ima_bprm_check(struct linux_binprm *bprm)
 	return 0;
 }
 
+static int ima_disabled = 0;
+static int __init ima_enabled(char *str)
+{
+	unsigned long enabled;
+
+	if (!strict_strtoul(str, 0, &enabled))
+		ima_disabled = enabled ? 0 : 1;
+
+	return 1;
+}
+__setup("ima=", ima_enabled);
+
 static int __init init_ima(void)
 {
 	int error;
 
+	if (ima_disabled) {
+		pr_info("IMA disabled at user request.\n");
+		return 0;
+	}
+
 	ima_iintcache_init();
 	error = ima_init();
 	ima_initialized = 1;