From 9a5df92374d65e2886b92e98dd7d873c533a83ff Mon Sep 17 00:00:00 2001 From: Marcel Holtmann Date: Sun, 30 Nov 2008 12:17:29 +0100 Subject: [PATCH] Bluetooth: Fix RFCOMM release oops when device is still in use It turns out that the following sequence of actions will reproduce the oops: 1. Create a new RFCOMM device (using RFCOMMCREATEDEV ioctl) 2. (Try to) open the device 3. Release the RFCOMM device (using RFCOMMRELEASEDEV ioctl) At this point, the "/dev/rfcomm*" device is still in use, but it is gone from the internal list, so the device id can be reused. 4. Create a new RFCOMM device with the same device id as before And now kobject will complain that the TTY already exists. (See http://lkml.org/lkml/2008/7/13/89 for a reproducible test-case.) This patch attempts to correct this by only removing the device from the internal list of devices at the final unregister stage, so that the id won't get reused until the device has been completely destructed. This should be safe as the RFCOMM_TTY_RELEASED bit will be set for the device and prevent the device from being reopened after it has been released. Based on a report from Vegard Nossum Signed-off-by: Marcel Holtmann --- net/bluetooth/rfcomm/tty.c | 30 +++++++++++++++++++++--------- 1 file changed, 21 insertions(+), 9 deletions(-) diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c index 1e4100bb0b65..111c6c858247 100644 --- a/net/bluetooth/rfcomm/tty.c +++ b/net/bluetooth/rfcomm/tty.c @@ -53,7 +53,7 @@ struct rfcomm_dev { char name[12]; int id; unsigned long flags; - int opened; + atomic_t opened; int err; bdaddr_t src; @@ -256,6 +256,8 @@ static int rfcomm_dev_add(struct rfcomm_dev_req *req, struct rfcomm_dlc *dlc) dev->flags = req->flags & ((1 << RFCOMM_RELEASE_ONHUP) | (1 << RFCOMM_REUSE_DLC)); + atomic_set(&dev->opened, 0); + init_waitqueue_head(&dev->wait); tasklet_init(&dev->wakeup_task, rfcomm_tty_wakeup, (unsigned long) dev); @@ -325,10 +327,10 @@ static void rfcomm_dev_del(struct rfcomm_dev *dev) { BT_DBG("dev %p", dev); - if (test_bit(RFCOMM_TTY_RELEASED, &dev->flags)) - BUG_ON(1); - else - set_bit(RFCOMM_TTY_RELEASED, &dev->flags); + BUG_ON(test_and_set_bit(RFCOMM_TTY_RELEASED, &dev->flags)); + + if (atomic_read(&dev->opened) > 0) + return; write_lock_bh(&rfcomm_dev_lock); list_del_init(&dev->list); @@ -684,9 +686,10 @@ static int rfcomm_tty_open(struct tty_struct *tty, struct file *filp) if (!dev) return -ENODEV; - BT_DBG("dev %p dst %s channel %d opened %d", dev, batostr(&dev->dst), dev->channel, dev->opened); + BT_DBG("dev %p dst %s channel %d opened %d", dev, batostr(&dev->dst), + dev->channel, atomic_read(&dev->opened)); - if (dev->opened++ != 0) + if (atomic_inc_return(&dev->opened) > 1) return 0; dlc = dev->dlc; @@ -742,9 +745,10 @@ static void rfcomm_tty_close(struct tty_struct *tty, struct file *filp) if (!dev) return; - BT_DBG("tty %p dev %p dlc %p opened %d", tty, dev, dev->dlc, dev->opened); + BT_DBG("tty %p dev %p dlc %p opened %d", tty, dev, dev->dlc, + atomic_read(&dev->opened)); - if (--dev->opened == 0) { + if (atomic_dec_and_test(&dev->opened)) { if (dev->tty_dev->parent) device_move(dev->tty_dev, NULL); @@ -758,6 +762,14 @@ static void rfcomm_tty_close(struct tty_struct *tty, struct file *filp) tty->driver_data = NULL; dev->tty = NULL; rfcomm_dlc_unlock(dev->dlc); + + if (test_bit(RFCOMM_TTY_RELEASED, &dev->flags)) { + write_lock_bh(&rfcomm_dev_lock); + list_del_init(&dev->list); + write_unlock_bh(&rfcomm_dev_lock); + + rfcomm_dev_put(dev); + } } rfcomm_dev_put(dev); -- GitLab