audit: store the auditd PID as a pid struct instead of pid_t

This is arguably the right thing to do, and will make it easier when
we start supporting multiple audit daemons in different namespaces.

Signed-off-by: Paul Moore <paul@paul-moore.com>

2 files changed, 58 insertions, 28 deletions

diff --git a/kernel/audit.c b/kernel/audit.c
index b40f3c4727e1..a2f7803a68d0 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -58,6 +58,7 @@
 #include <linux/rcupdate.h>
 #include <linux/mutex.h>
 #include <linux/gfp.h>
+#include <linux/pid.h>
 
 #include <linux/audit.h>
 
@@ -117,7 +118,7 @@ struct audit_net {
  * or the included spinlock for writing.
  */
 static struct auditd_connection {
-        int pid;
+        struct pid *pid;
         u32 portid;
         struct net *net;
         spinlock_t lock;
@@ -220,18 +221,41 @@ struct audit_reply {
  * Description:
  * Return 1 if the task is a registered audit daemon, 0 otherwise.
  */
-int auditd_test_task(const struct task_struct *task)
+int auditd_test_task(struct task_struct *task)
 {
         int rc;
 
         rcu_read_lock();
-        rc = (auditd_conn.pid && task->tgid == auditd_conn.pid ? 1 : 0);
+        rc = (auditd_conn.pid && auditd_conn.pid == task_tgid(task) ? 1 : 0);
         rcu_read_unlock();
 
         return rc;
 }
 
 /**
+ * auditd_pid_vnr - Return the auditd PID relative to the namespace
+ * @auditd: the auditd connection
+ *
+ * Description:
+ * Returns the PID in relation to the namespace, 0 on failure.  This function
+ * takes the RCU read lock internally, but if the caller needs to protect the
+ * auditd_connection pointer it should take the RCU read lock as well.
+ */
+static pid_t auditd_pid_vnr(const struct auditd_connection *auditd)
+{
+        pid_t pid;
+
+        rcu_read_lock();
+        if (!auditd || !auditd->pid)
+                pid = 0;
+        else
+                pid = pid_vnr(auditd->pid);
+        rcu_read_unlock();
+
+        return pid;
+}
+
+/**
  * audit_get_sk - Return the audit socket for the given network namespace
  * @net: the destination network namespace
  *
@@ -428,12 +452,17 @@ static int audit_set_failure(u32 state)
  * This function will obtain and drop network namespace references as
  * necessary.
  */
-static void auditd_set(int pid, u32 portid, struct net *net)
+static void auditd_set(struct pid *pid, u32 portid, struct net *net)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&auditd_conn.lock, flags);
-        auditd_conn.pid = pid;
+        if (auditd_conn.pid)
+                put_pid(auditd_conn.pid);
+        if (pid)
+                auditd_conn.pid = get_pid(pid);
+        else
+                auditd_conn.pid = NULL;
         auditd_conn.portid = portid;
         if (auditd_conn.net)
                 put_net(auditd_conn.net);
@@ -1059,11 +1088,13 @@ static int audit_set_feature(struct sk_buff *skb)
         return 0;
 }
 
-static int audit_replace(pid_t pid)
+static int audit_replace(struct pid *pid)
 {
+        pid_t pvnr;
         struct sk_buff *skb;
 
-        skb = audit_make_reply(0, AUDIT_REPLACE, 0, 0, &pid, sizeof(pid));
+        pvnr = pid_vnr(pid);
+        skb = audit_make_reply(0, AUDIT_REPLACE, 0, 0, &pvnr, sizeof(pvnr));
         if (!skb)
                 return -ENOMEM;
         return auditd_send_unicast_skb(skb);
@@ -1093,9 +1124,9 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
                 memset(&s, 0, sizeof(s));
                 s.enabled               = audit_enabled;
                 s.failure               = audit_failure;
-                rcu_read_lock();
-                s.pid                   = auditd_conn.pid;
-                rcu_read_unlock();
+                /* NOTE: use pid_vnr() so the PID is relative to the current
+                 *       namespace */
+                s.pid                   = auditd_pid_vnr(&auditd_conn);
                 s.rate_limit            = audit_rate_limit;
                 s.backlog_limit         = audit_backlog_limit;
                 s.lost                  = atomic_read(&audit_lost);
@@ -1121,36 +1152,36 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
                                 return err;
                 }
                 if (s.mask & AUDIT_STATUS_PID) {
-                        /* NOTE: we are using task_tgid_vnr() below because
-                         *       the s.pid value is relative to the namespace
-                         *       of the caller; at present this doesn't matter
-                         *       much since you can really only run auditd
-                         *       from the initial pid namespace, but something
-                         *       to keep in mind if this changes */
-                        int new_pid = s.pid;
+                        /* NOTE: we are using the vnr PID functions below
+                         *       because the s.pid value is relative to the
+                         *       namespace of the caller; at present this
+                         *       doesn't matter much since you can really only
+                         *       run auditd from the initial pid namespace, but
+                         *       something to keep in mind if this changes */
+                        pid_t new_pid = s.pid;
                         pid_t auditd_pid;
-                        pid_t requesting_pid = task_tgid_vnr(current);
+                        struct pid *req_pid = task_tgid(current);
+
+                        /* sanity check - PID values must match */
+                        if (new_pid != pid_vnr(req_pid))
+                                return -EINVAL;
 
                         /* test the auditd connection */
-                        audit_replace(requesting_pid);
+                        audit_replace(req_pid);
 
-                        rcu_read_lock();
-                        auditd_pid = auditd_conn.pid;
+                        auditd_pid = auditd_pid_vnr(&auditd_conn);
                         /* only the current auditd can unregister itself */
-                        if ((!new_pid) && (requesting_pid != auditd_pid)) {
-                                rcu_read_unlock();
+                        if ((!new_pid) && (new_pid != auditd_pid)) {
                                 audit_log_config_change("audit_pid", new_pid,
                                                         auditd_pid, 0);
                                 return -EACCES;
                         }
                         /* replacing a healthy auditd is not allowed */
                         if (auditd_pid && new_pid) {
-                                rcu_read_unlock();
                                 audit_log_config_change("audit_pid", new_pid,
                                                         auditd_pid, 0);
                                 return -EEXIST;
                         }
-                        rcu_read_unlock();
 
                         if (audit_enabled != AUDIT_OFF)
                                 audit_log_config_change("audit_pid", new_pid,
@@ -1158,8 +1189,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 
                         if (new_pid) {
                                 /* register a new auditd connection */
-                                auditd_set(new_pid,
-                                           NETLINK_CB(skb).portid,
+                                auditd_set(req_pid, NETLINK_CB(skb).portid,
                                            sock_net(NETLINK_CB(skb).sk));
                                 /* try to process any backlog */
                                 wake_up_interruptible(&kauditd_wait);
diff --git a/kernel/audit.h b/kernel/audit.h
index 18f3c2deeccf..4987ea2a4702 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -218,7 +218,7 @@ extern void audit_log_name(struct audit_context *context,
                            struct audit_names *n, const struct path *path,
                            int record_num, int *call_panic);
 
-extern int auditd_test_task(const struct task_struct *task);
+extern int auditd_test_task(struct task_struct *task);
 
 #define AUDIT_INODE_BUCKETS     32
 extern struct list_head audit_inode_hash[AUDIT_INODE_BUCKETS];