AUDIT: Clean up user message filtering

Don't look up the task by its pid and then use the syscall filtering
helper. Just implement our own filter helper which operates solely on
the information in the netlink_skb_parms. 

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

include/linux/audit.h

@@ -205,6 +205,7 @@ struct audit_sig_info {
 struct audit_buffer;
 struct audit_context;
 struct inode;
+struct netlink_skb_parms;
 
 #define AUDITSC_INVALID 0
 #define AUDITSC_SUCCESS 1
@@ -236,7 +237,7 @@ 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(int pid, int type);
+extern int audit_filter_user(struct netlink_skb_parms *cb, int type);
 #else
 #define audit_alloc(t) ({ 0; })
 #define audit_free(t) do { ; } while (0)
@@ -253,7 +254,7 @@ extern int audit_filter_user(int pid, 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(p,t) ({ 1; })
+#define audit_filter_user(cb,t) ({ 1; })
 #endif
 
 #ifdef CONFIG_AUDIT

kernel/audit.c

@@ -434,7 +434,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 		if (!audit_enabled && msg_type != AUDIT_USER_AVC)
 			return 0;
 
-		err = audit_filter_user(pid, msg_type);
+		err = audit_filter_user(&NETLINK_CB(skb), msg_type);
 		if (err == 1) {
 			err = 0;
 			ab = audit_log_start(NULL, GFP_KERNEL, msg_type);

kernel/auditsc.c

@@ -40,6 +40,7 @@
 #include <linux/personality.h>
 #include <linux/time.h>
 #include <linux/kthread.h>
+#include <linux/netlink.h>
 #include <asm/unistd.h>
 
 /* 0 = no checking
@@ -530,35 +531,62 @@ static enum audit_state audit_filter_syscall(struct task_struct *tsk,
 	return AUDIT_BUILD_CONTEXT;
 }
 
-int audit_filter_user(int pid, int type)
+static int audit_filter_user_rules(struct netlink_skb_parms *cb,
+			      struct audit_rule *rule,
+			      enum audit_state *state)
+{
+	int i;
+
+	for (i = 0; i < rule->field_count; i++) {
+		u32 field  = rule->fields[i] & ~AUDIT_NEGATE;
+		u32 value  = rule->values[i];
+		int result = 0;
+
+		switch (field) {
+		case AUDIT_PID:
+			result = (cb->creds.pid == value);
+			break;
+		case AUDIT_UID:
+			result = (cb->creds.uid == value);
+			break;
+		case AUDIT_GID:
+			result = (cb->creds.gid == value);
+			break;
+		case AUDIT_LOGINUID:
+			result = (cb->loginuid == value);
+			break;
+		}
+
+		if (rule->fields[i] & AUDIT_NEGATE)
+			result = !result;
+		if (!result)
+			return 0;
+	}
+	switch (rule->action) {
+	case AUDIT_NEVER:    *state = AUDIT_DISABLED;	    break;
+	case AUDIT_POSSIBLE: *state = AUDIT_BUILD_CONTEXT;  break;
+	case AUDIT_ALWAYS:   *state = AUDIT_RECORD_CONTEXT; break;
+	}
+	return 1;
+}
+
+int audit_filter_user(struct netlink_skb_parms *cb, int type)
 {
-	struct task_struct *tsk;
 	struct audit_entry *e;
 	enum audit_state   state;
 	int ret = 1;
 
-	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)) {
+		if (audit_filter_user_rules(cb, &e->rule, &state)) {
 			if (state == AUDIT_DISABLED)
 				ret = 0;
 			break;
 		}
 	}
 	rcu_read_unlock();
-	put_task_struct(tsk);
 
 	return ret; /* Audit by default */
-
 }
 
 /* This should be called with task_lock() held. */