linux-kernel - Re: [PATCH 3/7] SLIM main patch

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Date:	Thu, 24 Aug 2006 15:15:17 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"Serge E. Hallyn" <sergeh@...ibm.com>
Cc:	kjhall@...ibm.com, Benjamin LaHaise <bcrl@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	LSM ML <linux-security-module@...r.kernel.org>,
	David Safford <safford@...ibm.com>,
	Mimi Zohar <zohar@...ibm.com>
Subject: Re: [PATCH 3/7] SLIM main patch

Ar Iau, 2006-08-24 am 08:32 -0500, ysgrifennodd Serge E. Hallyn:
> > You also have to deal with existing mmap() mappings and outstanding I/O.
> 
> That she does.

I don't believe so from the patches.

> > 	SysV shared memory
> 
> standard mmap controls should handle this, right?

No its rather independant of mmap

> > 	mmap
> 
> She handles these.

I must have missed where it handles that.

> thread #2 is reading data from a pipe which is at a secret level, so how
> will it exploit that?  It can't write it to a lower integrity file...

Ok my example isn't quite right - I can create the pipes and do the
blocking in other patterns to get the result I mean. The problem is that
I can be blocked in a driver write() method before you raise the
security level and no change at the VFS level will be early enough to
stop it.

Another example would be

Type ^S
	thread #1
		write(console, padding, internalbuffersize);
		write(console, secret_buffer, data) [blocks]

	thread #2
		sleep to be sure #1 is blocked
		open secret file
		read(secret, secret_buffer, data);

Type ^Q

By the time you raise the security level due to the action of thread #2
I'm already blocked in tty_do_write() and have passed any vfs checks.

> The revoke(2) isn't quite right semantically, because it would revoke
> all users' access, right?  Rather, we want one process' rights to all
> files revoked, but other read/writers should still have access.

The core is the same, the question of specifically what you revoke is
different.


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