Subject: Re: [PATCH] unix: properly account for FDs passed over unix sockets

From: Hannes Frederic Sowa <[email-masked]>
Date: Tue, 29 Dec 2015 15:48:45 +0100

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: [email-masked]
> Suggested-by: Linus Torvalds <[email-masked]>
> Signed-off-by: Willy Tarreau <[email-masked]>

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