netdev - Re: [patches] a bunch of old bluetooth fixes

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Date:	Fri, 19 Dec 2014 11:28:35 +0100
From:	Marcel Holtmann <marcel@...tmann.org>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-bluetooth@...r.kernel.org
Subject: Re: [patches] a bunch of old bluetooth fixes

Hi Al,

> 	This stuff has been sitting in my queue since March; basically,
> several places in net/bluetooth assume that they are dealing with
> l2cap sockets, while it is possible to get an arbitrary socket to those.
> Results are not pretty.
> 	* HIDPCONNADD gets an arbitrary user-supplied socket; the code
> it calls (hidp_connection_add()) verifies that the socket is l2cap one,
> but before doing so it finds l2cap_pi(ctrl_sock->sk)->chan.  It's not
> that big a deal (it's only 5 words past the end of struct sock), but
> it's trivial to avoid and, in theory, we might end up oopsing here if
> we are very unlucky and it happens to hit an unmapped page just past
> the actual object ctrl_sock->sk sits in.
> 	* CMTP counterpart of that doesn't validate the socket at all.
> It proceeds to
>        s = __cmtp_get_session(&l2cap_pi(sock->sk)->chan->dst);
> which can very easily oops - here ->chan is already garbage and we
> proceed to dereference that.  As with HIDP, one needs CAP_NET_ADMIN to
> trigger that, but it's really a clear bug.  The only sanity check we
> do is verifying that nsock->sk->sk_state is equal to BT_CONNECTED,
> which is not unique to bluetooth, to put it mildly.  It's just 1,
> so a TCP_ESTABLISHED tcp socket will pass that check just fune.
> The fix is trivial...
> 	* BNEP situation is identical to CMTP one.
> 
> I've sent these patches back then (March 10), but they seem to have fallen
> through the cracks.  The bugs are still there and the fixes still apply.
> If you would prefer me to resend them after -rc1, just tell...

they must have really fallen through the cracks since I do not even remember them.

My take is that these should all go in before -rc1 and preferable also make it into stable. While you need CAP_NET_ADMIN capability, there are clear stupid bugs on our side.

Dave, we can prepare a pull request for these or do you want to take them directly into net tree?

Regards

Marcel

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