linux-kernel - Re: Really good idea to allow mmap(0, FIXED)?

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Message-Id: <200610082118.29200.mb@bu3sch.de>
Date:	Sun, 8 Oct 2006 21:18:29 +0200
From:	Michael Buesch <mb@...sch.de>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	David Wagner <daw-usenet@...erner.cs.berkeley.edu>,
	linux-kernel@...r.kernel.org
Subject: Re: Really good idea to allow mmap(0, FIXED)?

On Sunday 08 October 2006 02:22, Jeremy Fitzhardinge wrote:
> Though (*something_ops->thingy)() becomes a lot more interesting if 
> something_ops or ->thingy is NULL...

It's always very critical if a userspace program can modify some
data in the kernel. Be it function pointers or plain data.
Also consider something like:

if (task->uid == 0)
	allow_access_to_time_machine();
else
	return -EPERM;

Now if "task" may be a NULL pointer (due to a bug) it
can be exploited.

PS: Please don't drop me from the CC list ;)

-- 
Greetings Michael.
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