netdev - Re: [PATCH] net: Fix security_socket

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Message-Id: <201107230331.GHE48423.QFHJMFOLtOOSVF@I-love.SAKURA.ne.jp>
Date:	Sat, 23 Jul 2011 03:31:24 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	davem@...emloft.net
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.

Tetsuo Handa wrote:
> David Miller wrote:
> > 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.
> > 
> OK. Something like this? Not tested at all.

No. We can't compare destination address before entering __sys_sendmsg(), for
it is copied to kernel memory by verify_iovec()/verify_compat_iovec().

To be able to compare, we need to pass "struct sockaddr_storage address;" to
__sys_sendmsg(). Also, the content the kernel has to hold is not array of
"struct msghdr" but array of "struct sockaddr_storage".
It needs larger modification than expected.
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