From: Sahara keun-o.park@darkmatter.ae
[ Upstream commit b9ca5f8560af244489b4a1bc1ae88b341f24bc95 ]
Especially when a linked tty is used such as pty, the linked tty port's buf works have not been cancelled while master tty port's buf work has been cancelled. Since release_one_tty and flush_to_ldisc run in workqueue threads separately, when pty_cleanup happens and link tty port is freed, flush_to_ldisc tries to access freed port and port->itty, eventually it causes a panic. This patch utilizes the magic value with holding the tty_mutex to check if the tty->link is valid.
Fixes: 2b022ab7542d ("pty: cancel pty slave port buf's work in tty_release") Signed-off-by: Sahara keun-o.park@darkmatter.ae Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/tty/pty.c | 7 +++++++ drivers/tty/tty_io.c | 3 +++ 2 files changed, 10 insertions(+)
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c index c8a2e5b0eff76..0e10600f3884d 100644 --- a/drivers/tty/pty.c +++ b/drivers/tty/pty.c @@ -111,6 +111,12 @@ static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c) if (tty->stopped) return 0;
+ mutex_lock(&tty_mutex); + if (to->magic != TTY_MAGIC) { + mutex_unlock(&tty_mutex); + return -EIO; + } + if (c > 0) { spin_lock_irqsave(&to->port->lock, flags); /* Stuff the data into the input queue of the other end */ @@ -120,6 +126,7 @@ static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c) tty_flip_buffer_push(to->port); spin_unlock_irqrestore(&to->port->lock, flags); } + mutex_unlock(&tty_mutex); return c; }
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index b7effcfee91d8..acaf244859039 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1639,10 +1639,13 @@ static void release_one_tty(struct work_struct *work) struct tty_driver *driver = tty->driver; struct module *owner = driver->owner;
+ mutex_lock(&tty_mutex); if (tty->ops->cleanup) tty->ops->cleanup(tty);
tty->magic = 0; + mutex_unlock(&tty_mutex); + tty_driver_kref_put(driver); module_put(owner);