linux-kernel - Re: [PATCH 1/2] bluetooth: hci_ldisc: fix NULL-pointer dereference on tty

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Message-ID: <20120308115721.GB4497@localhost>
Date:	Thu, 8 Mar 2012 12:57:21 +0100
From:	Johan Hovold <jhovold@...il.com>
To:	Marcel Holtmann <marcel@...tmann.org>
Cc:	"Gustavo F. Padovan" <padovan@...fusion.mobi>,
	"David S. Miller" <davem@...emloft.net>,
	linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, stable <stable@...r.kernel.org>
Subject: Re: [PATCH 1/2] bluetooth: hci_ldisc: fix NULL-pointer dereference
 on tty_close

Hi Marcel,

On Wed, Mar 07, 2012 at 11:33:17AM -0800, Marcel Holtmann wrote:
> Hi Johan,
>
> > Do not close protocol driver until device has been unregistered.
> > 
> > This fixes a race between tty_close and hci_dev_open which can result in
> > a NULL-pointer dereference.
> > 
> > The line discipline closes the protocol driver while we may still have
> > hci_dev_open sleeping on the req_lock mutex resulting in a NULL-pointer
> > dereference when lock is acquired and hci_init_req called.

[...]

> what kernel version is this against? Our changes in bluetooth-next fixed
> some of the destruct handling.

This is against the latest rc as it needs to be fixed in 3.3, but I
missed a dependency to bluetooth-next as you point out below.

> Also hci_unregister_dev should be calling the destruct handler and thus
> your change is now accessing hu but it got freed already.

You're right, my patch depends on 010666a126fc ("Bluetooth: Make
hci-destruct callback optional") and 797fe796c4 ("Bluetooth: uart-ldisc:
Fix memory leak and remove destruct cb") from bluetooth-next. 

But since the latter one fixes a memory leak it should have been marked
for stable as well as pushed to Linus for 3.3, right?

Thanks,
Johan
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