Date: Fri, 18 Sep 2009 17:00:22 -0400 From: Garance A Drosihn <drosih@rpi.edu> To: Hideki EIRAKU <hdk_2@yahoo.co.jp>, pieter@thedarkside.nl Cc: freebsd-security@freebsd.org Subject: Re: Protecting against kernel NULL-pointer derefs Message-ID: <p06240802c6d9a4c04761@[128.113.24.47]> In-Reply-To: <20090919.001313.110616099.hdk_2@yahoo.co.jp> References: <4AAF4A64.3080906@thedarkside.nl> <20090919.001313.110616099.hdk_2@yahoo.co.jp>
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At 12:13 AM +0900 9/19/09, Hideki EIRAKU wrote:
>From: Pieter de Boer <pieter@thedarkside.nl>
>Subject: Protecting against kernel NULL-pointer derefs
>Date: Tue, 15 Sep 2009 10:03:48 +0200
>
>> - Are there unwanted side-effects of raising VM_MIN_ADDRESS?
>
>Mapping at address 0x0 is needed by some softwares using vm86 mode.
>For example, emulators/doscmd uses vm86 mode to emulate an old DOS
>environment. In this case, the address 0x0 - 0x3ff is used for an
>interrupt vector of emulated DOS world. If VM_MIN_ADDRESS is not
>zero, doscmd doesn't work. vm86 mode is in 32bit i386 architecture
>only, not in amd64 or other architectures.
Could we:
a) alter those programs so they didn't need that vector in page 0?
or
b) provide some system call or other facility which would allow
*that* process to use page 0?
--
Garance Alistair Drosehn = gad@gilead.netel.rpi.edu
Senior Systems Programmer or gad@freebsd.org
Rensselaer Polytechnic Institute or drosih@rpi.edu
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