From: daw@cs.berkeley.edu (David Wagner)
To: linux-kernel@vger.kernel.org
Subject: Re: Really good idea to allow mmap(0, FIXED)?
Date: Sun, 8 Oct 2006 02:03:07 +0000 (UTC) [thread overview]
Message-ID: <eg9m8r$8lf$1@taverner.cs.berkeley.edu> (raw)
In-Reply-To: 452844AB.2050406@goop.org
Jeremy Fitzhardinge wrote:
>David Wagner wrote:
>> Oops. Please ignore the PROT_EXEC. That is completely irrelevant.
>
>Though (*something_ops->thingy)() becomes a lot more interesting if
>something_ops or ->thingy is NULL...
If something_ops is NULL, catastrophic consequences ensue either way.
It's just as bad even if address 0 isn't mmap'ed with PROT_EXEC. For
example, suppose that .thingy is at offset 0x14 (say) and something_ops
is NULL. Then (*something_ops->thingy)() reads 4 bytes from address
0x14, treats what the 4 bytes read as an address, and transfers control
to that address. (On a 32-bit x86.) Since the latter address is under
the attacker's control, this means that the kernel has just transferred
control to an address of the attacker's choosing -- not good.
As you say, if something_ops->thingy is NULL, then mmap'ing address 0
with PROT_EXEC allows evil consequences.
next prev parent reply other threads:[~2006-10-08 2:03 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-05 18:59 Really good idea to allow mmap(0, FIXED)? Michael Buesch
2006-10-05 19:50 ` linux-os (Dick Johnson)
2006-10-06 14:40 ` Michael Buesch
2006-10-05 21:58 ` Alan Cox
2006-10-06 14:44 ` Michael Buesch
2006-10-07 11:23 ` Pavel Machek
2006-10-05 23:55 ` David Wagner
2006-10-06 4:34 ` Jeremy Fitzhardinge
2006-10-06 5:39 ` Jan Engelhardt
2006-10-06 19:47 ` David Wagner
2006-10-06 7:25 ` Arjan van de Ven
2006-10-06 10:36 ` Mikael Pettersson
2006-10-06 11:20 ` Arjan van de Ven
2006-10-06 19:43 ` David Wagner
2006-10-08 0:22 ` Jeremy Fitzhardinge
2006-10-08 2:03 ` David Wagner [this message]
2006-10-08 19:18 ` Michael Buesch
2006-10-06 14:55 ` Michael Buesch
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