commit 2cb5998b5f0ccc886fdda3509059eef297b49577
author Alan Cox <alan@redhat.com> Mon Oct 13 10:40:30 2008 +0100
committer Linus Torvalds <torvalds@linux-foundation.org> Mon Oct 13 09:51:41 2008 -0700
tree 9113731d3f892c2e164bfd05a7cf1a4b1713a619
parent 216ba023a96c04e8d3aabf83d5931c35b6e2dbbb

tty: the vhangup syscall is racy

We now have the infrastructure to sort this out but rather than teaching
the syscall tty lock rules we move the hard work into a tty helper

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/tty_io.c

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 913b502..b5f57d0 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -730,6 +730,25 @@
 EXPORT_SYMBOL(tty_vhangup);
 
 /**
+ *	tty_vhangup_self	-	process vhangup for own ctty
+ *
+ *	Perform a vhangup on the current controlling tty
+ */
+
+void tty_vhangup_self(void)
+{
+	struct tty_struct *tty;
+
+	mutex_lock(&tty_mutex);
+	tty = get_current_tty();
+	if (tty) {
+		tty_vhangup(tty);
+		tty_kref_put(tty);
+	}
+	mutex_unlock(&tty_mutex);
+}
+
+/**
  *	tty_hung_up_p		-	was tty hung up
  *	@filp: file pointer of tty
  *

fs/open.c

diff --git a/fs/open.c b/fs/open.c
index 07da935..5596049 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1141,8 +1141,7 @@
 asmlinkage long sys_vhangup(void)
 {
 	if (capable(CAP_SYS_TTY_CONFIG)) {
-		/* XXX: this needs locking */
-		tty_vhangup(current->signal->tty);
+		tty_vhangup_self();
 		return 0;
 	}
 	return -EPERM;

include/linux/tty.h

diff --git a/include/linux/tty.h b/include/linux/tty.h
index c30ed8d..e00393a 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -361,6 +361,7 @@
 extern int tty_signal(int sig, struct tty_struct *tty);
 extern void tty_hangup(struct tty_struct *tty);
 extern void tty_vhangup(struct tty_struct *tty);
+extern void tty_vhangup_self(void);
 extern void tty_unhangup(struct file *filp);
 extern int tty_hung_up_p(struct file *filp);
 extern void do_SAK(struct tty_struct *tty);