Re: [PATCH] unix: avoid use-after-free in ep_remove_wait_queue

Hi,

On Wed, Nov 11, 2015, at 17:12, Rainer Weikusat wrote:

Hannes Frederic Sowa [off-list ref] writes:

quoted

On Tue, Nov 10, 2015, at 22:55, Rainer Weikusat wrote:

quoted

An AF_UNIX datagram socket being the client in an n:1 association with
some server socket is only allowed to send messages to the server if the
receive queue of this socket contains at most sk_max_ack_backlog
datagrams.

[...]

quoted

This whole patch seems pretty complicated to me.

Can't we just remove the unix_recvq_full checks alltogether and unify
unix_dgram_poll with unix_poll?

If we want to be cautious we could simply make unix_max_dgram_qlen limit
the number of skbs which are in flight from a sending socket. The skb
destructor can then decrement this. This seems much simpler.

Would this work?

In the way this is intended to work, cf

http://marc.info/?t=115627606000002&r=1&w=2

Oh, I see, we don't limit closed but still referenced sockets. This
actually makes sense on how fd handling is implemented, just as a range
check.

Have you checked if we can somehow deregister the socket in the poll
event framework? You wrote that it does not provide such a function but
maybe it would be easy to add?

Thanks,
Hannes