linux-kernel - Re: [PATCH] Bluetooth: Fix null pointer dereference in l2cap_chan

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Message-id: <4FBAE9FE.9030807@samsung.com>
Date:	Tue, 22 May 2012 10:21:02 +0900
From:	Minho Ban <mhban@...sung.com>
To:	Gustavo Padovan <gustavo@...ovan.org>,
	Marcel Holtmann <marcel@...tmann.org>,
	Johan Hedberg <johan.hedberg@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Bluetooth: Fix null pointer dereference in l2cap_chan_send

On 05/22/2012 01:17 AM, Gustavo Padovan wrote:
> Hi Minho,
> 
> * Minho Ban <mhban@...sung.com> [2012-05-21 09:58:19 +0900]:
> 
>> If l2cap_chan_send is called will null conn it will cause kernel Oops.
>> This patch checks if conn is valid before entering l2cap_chan_send.
> 
> chan->conn should be always valid, and if not we have a bug somewhere else in
> the code and not in l2cap_chan_send(). It could be a locking problem maybe.
> Also check if you can reproduce this with latest bluetooth-next.
> 
> 	Gustavo
> 

Thanks for comment. I'm using bluetooth-next backporting to kernel 3.0
I wonder how do we guarantee chan->conn is valid if other thread release chan->lock
just after exit l2cap_chan_del.
It seem l2cap_chan_del is well protected with various mutex (eg, sk, conn, chan) but
that may not enough to prevent lock waiters from accessing object.

Regards,
Minho Ban
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