From: Justin Carlson <justin@cs.cmu.edu>
To: Carsten Langgaard <carstenl@mips.com>
Cc: linux-mips@oss.sgi.com
Subject: Re: __access_ok
Date: 17 Jun 2002 09:24:58 -0700 [thread overview]
Message-ID: <1024331098.1463.3.camel@localhost.localdomain> (raw)
In-Reply-To: <3D0DCDCB.252F5565@mips.com>
On Mon, 2002-06-17 at 04:53, Carsten Langgaard wrote:
> * Address valid if:
> - * - "addr" doesn't have any high-bits set
> - * - AND "size" doesn't have any high-bits set
> - * - AND "addr+size" doesn't have any high-bits set
> - * - OR we are in kernel mode.
> + * - In user mode and "addr" and "addr+size" in USEG (or XUSEG).
> + * - OR we are in kernel mode and "addr" and "addr+size" isn't in the
> + * area between USEG (XUSEG) and KSEG0.
You also need to test for high bit set in size. Otherwise, for example,
if a process was ok to access range 0x40000000-0x40003fff,
access_ok(0x40001000, 0xfffff100) would return 1. The addition will
wrap around, leading to all sorts of fun havoc.
-Justin
next prev parent reply other threads:[~2002-06-17 16:22 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-06-17 11:53 __access_ok Carsten Langgaard
2002-06-17 16:24 ` Justin Carlson [this message]
2002-06-18 7:44 ` __access_ok Carsten Langgaard
2002-06-17 19:55 ` __access_ok Jun Sun
2002-06-18 7:38 ` __access_ok Carsten Langgaard
2002-06-19 9:17 ` __access_ok Ralf Baechle
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