linux-kernel - Re: [PATCH, RFC] random: introduce getrandom(2) system call

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Message-ID: <20140723115253.9808.qmail@ns.horizon.com>
Date:	23 Jul 2014 07:52:53 -0400
From:	"George Spelvin" <linux@...izon.com>
To:	hannes@...essinduktion.org, tytso@....edu
Cc:	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux@...izon.com
Subject: Re: [PATCH, RFC] random: introduce getrandom(2) system call

I keep wishing for a more general solution.  For example, some way to
have a "spare" extra fd that could be accessed with a special O_NOFAIL
flag.

That would allow any number of library functions to not fail, such as
logging from nasty corner cases.

But you'd have to provide one per thread, and block non-fatal signals
while it was open, so you don't get reentrancy problems.  Ick.

This overly-specialized system call (and worse yet, a blocking
system call that you can't put into a poll() loop) just feels ugly
to me.  Is it *absolutely* necessary?

For example, how about simply making getentropy() a library function that
aborts if it can't open /dev/urandom?  If you're suffering fd exhaustion,
you're being DoSed already.
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