AUDIT: Optimise the audit-disabled case for discarding user messages

Also exempt USER_AVC message from being discarded to preserve 
existing behaviour for SE Linux.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

2 files changed, 30 insertions, 23 deletions

diff --git a/kernel/audit.c b/kernel/audit.c
index c1ab8dbbb67..09a37581213 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -429,25 +429,21 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 		break;
 	case AUDIT_USER:
 	case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG:
-		read_lock(&tasklist_lock);
-		tsk = find_task_by_pid(pid);
-		if (tsk)
-			get_task_struct(tsk);
-		read_unlock(&tasklist_lock);
-		if (!tsk)
-			return -ESRCH;
-
-		if (audit_enabled && audit_filter_user(tsk, msg_type)) {
-			    ab = audit_log_start(NULL, msg_type);
-			    if (ab) {
-				    audit_log_format(ab,
-						     "user pid=%d uid=%u auid=%u msg='%.1024s'",
-						     pid, uid, loginuid, (char *)data);
-				    audit_set_pid(ab, pid);
-				    audit_log_end(ab);
-			    }
+		if (!audit_enabled && msg_type != AUDIT_USER_AVC)
+			return 0;
+
+		err = audit_filter_user(pid, msg_type);
+		if (err == 1) {
+			err = 0;
+			ab = audit_log_start(NULL, msg_type);
+			if (ab) {
+				audit_log_format(ab,
+						 "user pid=%d uid=%u auid=%u msg='%.1024s'",
+						 pid, uid, loginuid, (char *)data);
+				audit_set_pid(ab, pid);
+				audit_log_end(ab);
+			}
 		}
-		put_task_struct(tsk);
 		break;
 	case AUDIT_ADD:
 	case AUDIT_DEL:
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index cb8a4494515..fc858b0c044 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -530,22 +530,33 @@ static enum audit_state audit_filter_syscall(struct task_struct *tsk,
 	return AUDIT_BUILD_CONTEXT;
 }
 
-int audit_filter_user(struct task_struct *tsk, int type)
+int audit_filter_user(int pid, int type)
 {
+	struct task_struct *tsk;
 	struct audit_entry *e;
 	enum audit_state   state;
+	int ret = 1;
 
-	if (audit_pid && tsk->pid == audit_pid)
-		return AUDIT_DISABLED;
+	read_lock(&tasklist_lock);
+	tsk = find_task_by_pid(pid);
+	if (tsk)
+		get_task_struct(tsk);
+	read_unlock(&tasklist_lock);
+
+	if (!tsk)
+		return -ESRCH;
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_USER], list) {
 		if (audit_filter_rules(tsk, &e->rule, NULL, &state)) {
-			rcu_read_unlock();
-			return state != AUDIT_DISABLED;
+			if (state == AUDIT_DISABLED)
+				ret = 0;
+			break;
 		}
 	}
 	rcu_read_unlock();
+	put_task_struct(tsk);
+
 	return 1; /* Audit by default */
 
 }