[PATCH 42/76] tty: the vhangup syscall is racy

Alan Cox
2008-10-05T16:19:52Z

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>
---

drivers/char/tty_io.c | 19 +++++++++++++++++++
fs/open.c | 3 +--
2 files changed, 20 insertions(+), 2 deletions(-)

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 @@ void tty_vhangup(struct tty_struct *tty)
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
*
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 @@ EXPORT_SYMBOL(sys_close);
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;