Messages in this thread | | | From | Rainer Weikusat <> | Subject | Re: [PATCH] unix: avoid use-after-free in ep_remove_wait_queue | Date | Wed, 11 Nov 2015 16:12:27 +0000 |
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Hannes Frederic Sowa <hannes@stressinduktion.org> writes: > On Tue, Nov 10, 2015, at 22:55, Rainer Weikusat wrote: >> 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.
[...]
> 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
only if the limit would also apply to sockets which didn't sent anything so far. Which means it'll end up in the exact same situation as before: Sending something using a certain socket may not be possible because of data sent by other sockets, so either, code trying to send using this sockets ends up busy-waiting for "space again available" despite it's trying to use select/ poll/ epolll/ $whatnot to get notified of this condition and sleep until then or this notification needs to be propagated to sleeping threads which didn't get to send anything yet.
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