2008-01-07 05:38:08

by Dave Young

Subject: [PATCH] bluetooth : rfcomm tty BUG_ON() code fix

1) In tty.c the BUG_ON at line 115 will never be called, because the the before list_del_init in this same function.
115 BUG_ON(!list_empty(&dev->list));
So move the list_del_init to rfcomm_dev_del

2) The rfcomm_dev_del could be called from diffrent path (rfcomm_tty_hangup/rfcomm_dev_state_change/rfcomm_release_dev),
So add another BUG_ON when the rfcomm_dev_del is called more than one time.

Signed-off-by: Dave Young <[email protected]>

---
net/bluetooth/rfcomm/tty.c | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)

diff -upr linux/net/bluetooth/rfcomm/tty.c linux.new/net/bluetooth/rfcomm/tty.c
--- linux/net/bluetooth/rfcomm/tty.c 2008-01-07 13:20:17.000000000 +0800
+++ linux.new/net/bluetooth/rfcomm/tty.c 2008-01-07 13:25:17.000000000 +0800
@@ -95,9 +95,10 @@ static void rfcomm_dev_destruct(struct r

BT_DBG("dev %p dlc %p", dev, dlc);

- write_lock_bh(&rfcomm_dev_lock);
- list_del_init(&dev->list);
- write_unlock_bh(&rfcomm_dev_lock);
+ /* Refcount should only hit zero when called from rfcomm_dev_del()
+ which will have taken us off the list. Everything else are
+ refcounting bugs. */
+ BUG_ON(!list_empty(&dev->list));

rfcomm_dlc_lock(dlc);
/* Detach DLC if it's owned by this dev */
@@ -109,11 +110,6 @@ static void rfcomm_dev_destruct(struct r

tty_unregister_device(rfcomm_tty_driver, dev->id);

- /* Refcount should only hit zero when called from rfcomm_dev_del()
- which will have taken us off the list. Everything else are
- refcounting bugs. */
- BUG_ON(!list_empty(&dev->list));
-
kfree(dev);

/* It's safe to call module_put() here because socket still
@@ -313,7 +309,15 @@ static void rfcomm_dev_del(struct rfcomm
{
BT_DBG("dev %p", dev);

- set_bit(RFCOMM_TTY_RELEASED, &dev->flags);
+ if (test_bit(RFCOMM_TTY_RELEASED, &dev->flags))
+ BUG_ON(1);
+ else
+ set_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);
}

2008-01-11 06:23:32

by David Miller

Subject: Re: [PATCH] bluetooth : rfcomm tty BUG_ON() code fix

From: Dave Young <[email protected]>
Date: Mon, 7 Jan 2008 13:41:22 +0800

> 1) In tty.c the BUG_ON at line 115 will never be called, because the the before list_del_init in this same function.
> 115 BUG_ON(!list_empty(&dev->list));
> So move the list_del_init to rfcomm_dev_del
>
> 2) The rfcomm_dev_del could be called from diffrent path (rfcomm_tty_hangup/rfcomm_dev_state_change/rfcomm_release_dev),
> So add another BUG_ON when the rfcomm_dev_del is called more than one time.
>
> Signed-off-by: Dave Young <[email protected]>

Applied, thanks Dave.