audit: add tty field to LOGIN event

The tty field was missing from AUDIT_LOGIN events.

Refactor code to create a new function audit_get_tty(), using it to
replace the call in audit_log_task_info() and to add it to
audit_log_set_loginuid().  Lock and bump the kref to protect it, adding
audit_put_tty() alias to decrement it.

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

3 files changed, 35 insertions, 15 deletions

diff --git a/include/linux/audit.h b/include/linux/audit.h
index b40ed5df5542..32cdafb312d8 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -26,6 +26,7 @@
 #include <linux/sched.h>
 #include <linux/ptrace.h>
 #include <uapi/linux/audit.h>
+#include <linux/tty.h>
 
 #define AUDIT_INO_UNSET ((unsigned long)-1)
 #define AUDIT_DEV_UNSET ((dev_t)-1)
@@ -343,6 +344,23 @@ static inline unsigned int audit_get_sessionid(struct task_struct *tsk)
         return tsk->sessionid;
 }
 
+static inline struct tty_struct *audit_get_tty(struct task_struct *tsk)
+{
+        struct tty_struct *tty = NULL;
+        unsigned long flags;
+
+        spin_lock_irqsave(&tsk->sighand->siglock, flags);
+        if (tsk->signal)
+                tty = tty_kref_get(tsk->signal->tty);
+        spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
+        return tty;
+}
+
+static inline void audit_put_tty(struct tty_struct *tty)
+{
+        tty_kref_put(tty);
+}
+
 extern void __audit_ipc_obj(struct kern_ipc_perm *ipcp);
 extern void __audit_ipc_set_perm(unsigned long qbytes, uid_t uid, gid_t gid, umode_t mode);
 extern void __audit_bprm(struct linux_binprm *bprm);
@@ -500,6 +518,12 @@ static inline unsigned int audit_get_sessionid(struct task_struct *tsk)
 {
         return -1;
 }
+static inline struct tty_struct *audit_get_tty(struct task_struct *tsk)
+{
+        return NULL;
+}
+static inline void audit_put_tty(struct tty_struct *tty)
+{ }
 static inline void audit_ipc_obj(struct kern_ipc_perm *ipcp)
 { }
 static inline void audit_ipc_set_perm(unsigned long qbytes, uid_t uid,
diff --git a/kernel/audit.c b/kernel/audit.c
index f52fbefede09..384374a1d232 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -64,7 +64,6 @@
 #include <linux/security.h>
 #endif
 #include <linux/freezer.h>
-#include <linux/tty.h>
 #include <linux/pid_namespace.h>
 #include <net/netns/generic.h>
 
@@ -1871,21 +1870,14 @@ void audit_log_task_info(struct audit_buffer *ab, struct task_struct *tsk)
 {
         const struct cred *cred;
         char comm[sizeof(tsk->comm)];
-        char *tty;
+        struct tty_struct *tty;
 
         if (!ab)
                 return;
 
         /* tsk == current */
         cred = current_cred();
-
-        spin_lock_irq(&tsk->sighand->siglock);
-        if (tsk->signal && tsk->signal->tty && tsk->signal->tty->name)
-                tty = tsk->signal->tty->name;
-        else
-                tty = "(none)";
-        spin_unlock_irq(&tsk->sighand->siglock);
-
+        tty = audit_get_tty(tsk);
         audit_log_format(ab,
                          " ppid=%d pid=%d auid=%u uid=%u gid=%u"
                          " euid=%u suid=%u fsuid=%u"
@@ -1901,11 +1893,11 @@ void audit_log_task_info(struct audit_buffer *ab, struct task_struct *tsk)
                          from_kgid(&init_user_ns, cred->egid),
                          from_kgid(&init_user_ns, cred->sgid),
                          from_kgid(&init_user_ns, cred->fsgid),
-                         tty, audit_get_sessionid(tsk));
-
+                         tty ? tty_name(tty) : "(none)",
+                         audit_get_sessionid(tsk));
+        audit_put_tty(tty);
         audit_log_format(ab, " comm=");
         audit_log_untrustedstring(ab, get_task_comm(comm, tsk));
-
         audit_log_d_path_exe(ab, tsk->mm);
         audit_log_task_context(ab);
 }
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 195ffaee50b9..71e14d836e69 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1980,6 +1980,7 @@ static void audit_log_set_loginuid(kuid_t koldloginuid, kuid_t kloginuid,
 {
         struct audit_buffer *ab;
         uid_t uid, oldloginuid, loginuid;
+        struct tty_struct *tty;
 
         if (!audit_enabled)
                 return;
@@ -1987,14 +1988,17 @@ static void audit_log_set_loginuid(kuid_t koldloginuid, kuid_t kloginuid,
         uid = from_kuid(&init_user_ns, task_uid(current));
         oldloginuid = from_kuid(&init_user_ns, koldloginuid);
         loginuid = from_kuid(&init_user_ns, kloginuid),
+        tty = audit_get_tty(current);
 
         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_LOGIN);
         if (!ab)
                 return;
         audit_log_format(ab, "pid=%d uid=%u", task_pid_nr(current), uid);
         audit_log_task_context(ab);
-        audit_log_format(ab, " old-auid=%u auid=%u old-ses=%u ses=%u res=%d",
-                         oldloginuid, loginuid, oldsessionid, sessionid, !rc);
+        audit_log_format(ab, " old-auid=%u auid=%u tty=%s old-ses=%u ses=%u res=%d",
+                         oldloginuid, loginuid, tty ? tty_name(tty) : "(none)",
+                         oldsessionid, sessionid, !rc);
+        audit_put_tty(tty);
         audit_log_end(ab);
 }