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Re: Insertion of die_if_kernel in unaligned.c

To: Carsten Langgaard <carstenl@mips.com>
Subject: Re: Insertion of die_if_kernel in unaligned.c
From: Ralf Baechle <ralf@oss.sgi.com>
Date: Thu, 3 May 2001 14:21:14 -0300
Cc: linux-mips@oss.sgi.com
In-reply-to: <3AF13558.F26941EE@mips.com>; from carstenl@mips.com on Thu, May 03, 2001 at 12:39:20PM +0200
References: <3AF13558.F26941EE@mips.com>
Sender: owner-linux-mips@oss.sgi.com
User-agent: Mutt/1.2.5i
On Thu, May 03, 2001 at 12:39:20PM +0200, Carsten Langgaard wrote:

> In the latest version of arch/mips/kernel/unaligned.c, there has been
> inserted some calls to the die_if_kernel, which check if we are running
> in kernel mode and if so dies.
> I'm not so sure this is the right thing to do, the floating point
> emulator will in some cases generate an address error (e.g. if emulating
> a swc1 to an unaligned address). The result is that an user application
> can crash the kernel.

They're wrong and what's worse, I knew about them.  The unaligned from
kernelspace case can also be triggered from the network stack so this
leaves machines open to remote DoS.

  Ralf

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