From: Jan Engelhardt <jengelh@linux01.gwdg.de>
To: Kyle Moffett <mrmacman_g4@mac.com>
Cc: Michael Buesch <mbuesch@freenet.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Mapping to 0x0
Date: Sat, 25 Feb 2006 23:10:39 +0100 (MET) [thread overview]
Message-ID: <Pine.LNX.4.61.0602252309150.10677@yvahk01.tjqt.qr> (raw)
In-Reply-To: <BE7AD56A-27CA-465C-A4C6-774E8C074EF0@mac.com>
>> I am playing around with it. I did the attached code. It is a usermode
>> program, which tries to map NULL, and a kernel module, which calls a NULL
>> pointer. The file badcode.bin contains an i386 ud2 instruction. When
>> loading the kernel module, while the usermode program is executing, I get
>> the usual NULL pointer dereference oops:
>
> You need to trigger the null pointer dereference from within the userspace
> program that maps NULL. The reason your test doesn't do anything is that it is
> the insmod tool whose address space gets used, as opposed to your nulltest
> program.
>
Think of a device driver which dereferences on read() or write() or ioctl.
Then the userspace program gets its chance, does not it?
Jan Engelhardt
--
next prev parent reply other threads:[~2006-02-25 22:10 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-22 14:10 Mapping to 0x0 Jan Engelhardt
2006-02-22 14:31 ` linux-os (Dick Johnson)
2006-02-23 17:14 ` Jan Engelhardt
2006-02-23 17:45 ` linux-os (Dick Johnson)
2006-02-24 11:37 ` Michael Buesch
2006-02-25 18:25 ` Kyle Moffett
2006-02-25 22:10 ` Jan Engelhardt [this message]
[not found] <5J30B-8wi-7@gated-at.bofh.it>
2006-02-24 2:17 ` Robert Hancock
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