[PATCH] Re: Got suggestions to reduce the locks in stacker.c?

jmorrisat_private

On Tue, 23 Jul 2002, Chris Wright wrote:

> This seems like a reasonable approach.  It allows an easy way for module
> authors to give an unload/can't unload override switch.

Ok, included below is a patch which does this for the capability module.  

Loading as a module with the parameter develop_mode=1 allows it to be 
unloaded.  Otherwise, it's unloadable via normal means.

Actually, I wonder if this should instead be a compile-time configuration 
option, like the SELinux development mode option.  It's really only useful 
to kernel developers, so making it a runtime option for everyone may not 
be the best approach.  If this were to be a compilation option, perhaps it 
could be a single option under either the security or kernel hacking 
config sections, to be used by all modules (including for any other 
developer bypasses).  Thoughts?

- James
-- 
James Morris
<jmorrisat_private>

diff -urN -X dontdiff lsm-2.5/security/capability.c lsm-2.5.w1/security/capability.c

--- lsm-2.5/security/capability.c	Tue Jul 23 11:24:17 2002
+++ lsm-2.5.w1/security/capability.c	Wed Jul 24 23:04:07 2002
@@ -1201,10 +1201,44 @@
 
 #if defined(CONFIG_SECURITY_CAPABILITIES_MODULE)
 #define MY_NAME THIS_MODULE->name
+
+static int develop_mode = 0;
+
+static int can_unload(void)
+{
+	return develop_mode ? 0 : -EBUSY;
+}
+
+static int set_unloadable(void)
+{
+	if (!mod_member_present(&__this_module, can_unload))
+		return -EBUSY;
+		
+	__this_module.can_unload = can_unload;
+	return 0;
+}
+
 #else
 #define MY_NAME "capability"
+static inline int set_unloadable(void) { return 0; }
 #endif
 
+static void unregister_self(void)
+{
+	/* remove ourselves from the security framework */
+	if (secondary) {
+		if (mod_unreg_security (MY_NAME, &capability_ops))
+			printk (KERN_INFO "Failure unregistering capabilities "
+				"with primary module.\n");
+		return;
+	}
+
+	if (unregister_security (&capability_ops)) {
+		printk (KERN_INFO
+			"Failure unregistering capabilities with the kernel\n");
+	}
+}
+
 static int __init capability_init (void)
 {
 	/* register ourselves with the security framework */
@@ -1219,28 +1253,24 @@
 		}
 		secondary = 1;
 	}
+
+	if (set_unloadable())
+		unregister_self();
+	
 	printk (KERN_INFO "Capability LSM initialized\n");
 	return 0;
 }
 
 static void __exit capability_exit (void)
 {
-	/* remove ourselves from the security framework */
-	if (secondary) {
-		if (mod_unreg_security (MY_NAME, &capability_ops))
-			printk (KERN_INFO "Failure unregistering capabilities "
-				"with primary module.\n");
-		return;
-	}
-
-	if (unregister_security (&capability_ops)) {
-		printk (KERN_INFO
-			"Failure unregistering capabilities with the kernel\n");
-	}
+	unregister_self();
 }
 
 module_init (capability_init);
 module_exit (capability_exit);
+
+MODULE_PARM(develop_mode, "i");
+MODULE_PARM_DESC(develop_mode, "enable development mode: allows module unload");
 
 MODULE_DESCRIPTION("Standard Linux Capabilities Security Module");
 MODULE_LICENSE("GPL");

_______________________________________________
linux-security-module mailing list
linux-security-moduleat_private
http://mail.wirex.com/mailman/listinfo/linux-security-module
