netdev - Re: [PATCH] LSM: Add security_socket_post_accept() and security_socket_post_recv

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Message-ID: <20090422065443.GC4221@bx9.net>
Date:	Tue, 21 Apr 2009 23:54:43 -0700
From:	Greg Lindahl <greg@...kko.com>
To:	David Miller <davem@...emloft.net>
Cc:	penguin-kernel@...ove.sakura.ne.jp, paul.moore@...com,
	linux-security-module@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] LSM: Add security_socket_post_accept() and
	security_socket_post_recv_datagram().

On Tue, Apr 21, 2009 at 11:46:18PM -0700, David Miller wrote:

> EAGAIN does not happen if the application calls poll(), gets
> an indication that connections are available, and then
> immediately calls accept() on the indicated FD.

I have observed it recently and historically, and not by calling
accept() repeatedly. I don't know what you mean by "immediately" since I
don't think you're advocating race conditions; the other end can
always exit/reset/whatever between the poll() and the accept().

> If overly anal apps "code for it" that is entirely besides the point.
> What we have to be concerned for, from a kernel behavioral standpoint,
> is that some apps "might not code for it".  This is why we don't
> change behavior.

I am suggesting that you survey actual apps. If you find that they're
all overly anal, then maybe you've learned something about EAGAIN
already happening today. I assure you that the co-worker who stuck in
the "ignore EAGAIN without logging it" only did so because he saw it
fairly frequently. He's that way.

-- greg

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