netdev - Re: [PATCH] net: Fix security_socket

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Message-Id: <20110722.082224.688620059032914637.davem@davemloft.net>
Date:	Fri, 22 Jul 2011 08:22:24 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	penguin-kernel@...ove.SAKURA.ne.jp
Cc:	casey@...aufler-ca.com, anton@...ba.org, netdev@...r.kernel.org,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH] net: Fix security_socket_sendmsg() bypass problem.

From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Date: Sat, 23 Jul 2011 00:12:53 +0900

> I think the regression for SMACK can be fixed with below patch.
> 
> Should I pass nosec flags down to "struct security_operations"->sendmsg()
> so that SELinux checks sock_has_perm() for only once when multiple different
> destination's addresses are passed to sendmmsg()?
> 
> static int selinux_socket_sendmsg(struct socket *sock, struct msghdr *msg,
> 				  int size, int nosec)
> {
> 	return nosec ? 0 : sock_has_perm(current, sock->sk, SOCKET__WRITE);
> }

Ugh, this takes away a non-trivial part of the performance gain of
sendmmsg().

I would instead rather that you check ahead of time whether this
actually is a send to different addresses.  If they are all the
same, keep the nosec code path.
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