[PATCH] mark context of syscall entered with no rules as dummy

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/audit.h

@@ -329,6 +329,11 @@ extern void __audit_inode(const char *name, const struct inode *inode);
 extern void __audit_inode_child(const char *dname, const struct inode *inode,
 				const struct inode *parent);
 extern void __audit_inode_update(const struct inode *inode);
+static inline int audit_dummy_context(void)
+{
+	void *p = current->audit_context;
+	return !p || *(int *)p;
+}
 static inline void audit_getname(const char *name)
 {
 	if (unlikely(current->audit_context))
@@ -416,6 +421,7 @@ extern int audit_n_rules;
 #define audit_free(t) do { ; } while (0)
 #define audit_syscall_entry(ta,a,b,c,d,e) do { ; } while (0)
 #define audit_syscall_exit(f,r) do { ; } while (0)
+#define audit_dummy_context() 1
 #define audit_getname(n) do { ; } while (0)
 #define audit_putname(n) do { ; } while (0)
 #define __audit_inode(n,i) do { ; } while (0)

kernel/auditsc.c

@@ -177,6 +177,7 @@ struct audit_aux_data_path {
 
 /* The per-task audit context. */
 struct audit_context {
+	int		    dummy;	/* must be the first element */
 	int		    in_syscall;	/* 1 if task is in a syscall */
 	enum audit_state    state;
 	unsigned int	    serial;     /* serial number for record */
@@ -517,7 +518,7 @@ static inline struct audit_context *audit_get_context(struct task_struct *tsk,
 	context->return_valid = return_valid;
 	context->return_code  = return_code;
 
-	if (context->in_syscall && !context->auditable) {
+	if (context->in_syscall && !context->dummy && !context->auditable) {
 		enum audit_state state;
 
 		state = audit_filter_syscall(tsk, context, &audit_filter_list[AUDIT_FILTER_EXIT]);
@@ -1069,7 +1070,8 @@ void audit_syscall_entry(int arch, int major,
 	context->argv[3]    = a4;
 
 	state = context->state;
-	if (state == AUDIT_SETUP_CONTEXT || state == AUDIT_BUILD_CONTEXT)
+	context->dummy = !audit_n_rules;
+	if (!context->dummy && (state == AUDIT_SETUP_CONTEXT || state == AUDIT_BUILD_CONTEXT))
 		state = audit_filter_syscall(tsk, context, &audit_filter_list[AUDIT_FILTER_ENTRY]);
 	if (likely(state == AUDIT_DISABLED))
 		return;