[PATCH 4.4 24/72] audit: add tty field to LOGIN event

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Richard Guy Briggs <rgb@xxxxxxxxxx>

commit db0a6fb5d97afe01fd9c47d37c6daa82d4d4001d upstream.

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@xxxxxxxxxx>
Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 include/linux/audit.h |   24 ++++++++++++++++++++++++
 kernel/audit.c        |   18 +++++-------------
 kernel/auditsc.c      |    8 ++++++--
 3 files changed, 35 insertions(+), 15 deletions(-)

--- 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)
@@ -239,6 +240,23 @@ static inline unsigned int audit_get_ses
 	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);
@@ -410,6 +428,12 @@ static inline unsigned int audit_get_ses
 {
 	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,
--- 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>
 
@@ -1876,21 +1875,14 @@ void audit_log_task_info(struct audit_bu
 {
 	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"
@@ -1906,11 +1898,11 @@ void audit_log_task_info(struct audit_bu
 			 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);
 }
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1976,6 +1976,7 @@ static void audit_log_set_loginuid(kuid_
 {
 	struct audit_buffer *ab;
 	uid_t uid, oldloginuid, loginuid;
+	struct tty_struct *tty;
 
 	if (!audit_enabled)
 		return;
@@ -1983,14 +1984,17 @@ static void audit_log_set_loginuid(kuid_
 	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);
 }