linux-kernel - Re: [PATCH] unix: properly account for FDs passed over unix sockets

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Date:	Tue, 29 Dec 2015 15:48:45 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Willy Tarreau <w@....eu>, "David S. Miller" <davem@...emloft.net>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Eric Dumazet <edumazet@...gle.com>, socketpair@...il.com
Subject: Re: [PATCH] unix: properly account for FDs passed over unix sockets

On 28.12.2015 15:14, Willy Tarreau wrote:
> It is possible for a process to allocate and accumulate far more FDs than
> the process' limit by sending them over a unix socket then closing them
> to keep the process' fd count low.
>
> This change addresses this problem by keeping track of the number of FDs
> in flight per user and preventing non-privileged processes from having
> more FDs in flight than their configured FD limit.
>
> Reported-by: socketpair@...il.com
> Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Willy Tarreau <w@....eu>

Thanks for the patch!

I think this does not close the DoS attack completely as we duplicate 
fds if the reader uses MSG_PEEK on the unix domain socket and thus 
clones the fd. Have I overlooked something?

Thanks,
Hannes

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