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>

3 files changed, 34 insertions, 26 deletions

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 5d1a9dda5acb..77adef640537 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -51,7 +51,8 @@
 #define AUDIT_WATCH_LIST        1009    /* List all file/dir watches */
 #define AUDIT_SIGNAL_INFO       1010    /* Get info about sender of signal to auditd */
 
-#define AUDIT_FIRST_USER_MSG    1100    /* Userspace messages uninteresting to kernel */
+#define AUDIT_FIRST_USER_MSG    1100    /* Userspace messages mostly uninteresting to kernel */
+#define AUDIT_USER_AVC          1107    /* We filter this differently */
 #define AUDIT_LAST_USER_MSG     1199
  
 #define AUDIT_DAEMON_START      1200    /* Daemon startup record */
@@ -235,7 +236,7 @@ extern int audit_socketcall(int nargs, unsigned long *args);
 extern int audit_sockaddr(int len, void *addr);
 extern int audit_avc_path(struct dentry *dentry, struct vfsmount *mnt);
 extern void audit_signal_info(int sig, struct task_struct *t);
-extern int audit_filter_user(struct task_struct *tsk, int type);
+extern int audit_filter_user(int pid, int type);
 #else
 #define audit_alloc(t) ({ 0; })
 #define audit_free(t) do { ; } while (0)
@@ -252,7 +253,7 @@ extern int audit_filter_user(struct task_struct *tsk, int type);
 #define audit_sockaddr(len, addr) ({ 0; })
 #define audit_avc_path(dentry, mnt) ({ 0; })
 #define audit_signal_info(s,t) do { ; } while (0)
-#define audit_filter_user(struct ({ 1; })
+#define audit_filter_user(p,t) ({ 1; })
 #endif
 
 #ifdef CONFIG_AUDIT
diff --git a/kernel/audit.c b/kernel/audit.c
index c1ab8dbbb67b..09a37581213b 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 cb8a44945157..fc858b0c044a 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 */
 
 }