diff options
| author | Sahara <keun-o.park@darkmatter.ae> | 2019-02-11 11:09:15 +0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-03-28 01:28:23 +0900 |
| commit | b9ca5f8560af244489b4a1bc1ae88b341f24bc95 (patch) | |
| tree | 2fa81b283d5ff446fe29cf26aea8b6c05db22479 /drivers/tty | |
| parent | 75ddbc1fb11efac87b611d48e9802f6fe2bb2163 (diff) | |
tty: pty: Fix race condition between release_one_tty and pty_write
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>
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | drivers/tty/pty.c | 7 | ||||
| -rw-r--r-- | drivers/tty/tty_io.c | 3 |
2 files changed, 10 insertions, 0 deletions
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c index 00099a8439d2..ef72031ab5b9 100644 --- a/drivers/tty/pty.c +++ b/drivers/tty/pty.c @@ -116,6 +116,12 @@ 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 */ @@ -125,6 +131,7 @@ 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 5fa250157025..c27777f3b8c4 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1448,10 +1448,13 @@ 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); |