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Date: Mon, 26 Aug 2002 21:33:04 +0100
From: Russell King <rmk@arm.linux.org.uk>
To: Jeff Dike <jdike@karaya.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: copy_to_user to a kmapped address
Message-ID: <20020826213304.I4763@flint.arm.linux.org.uk>
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In-Reply-To: <200208262119.QAA03617@ccure.karaya.com>; from jdike@karaya.com on Mon, Aug 26, 2002 at 04:19:37PM -0500
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On Mon, Aug 26, 2002 at 04:19:37PM -0500, Jeff Dike wrote:
> Is this (in file_read_actor) bogus or am I missing something?
> 
> 1621            kaddr = kmap(page);
> 1622            left = __copy_to_user(desc->buf, kaddr + offset, size);
> 1623            kunmap(page);
> 
> It seems to me that copy_to_user should be able to assume that the destination
> address is a user address.
> 
> This is biting me because I'm moving the UML kernel into a separate address
> space, so there's no way, in general, to tell the difference between a kernel
> address and a userspace address.

Umm, that's copying from kaddr + offset _to_ desc->buf.  desc->buf
should be the user space address, and kaddr + offset a kernel address:

unsigned long __copy_to_user(void *to, const void *from, unsigned long n)

-- 
Russell King (rmk@arm.linux.org.uk)                The developer of ARM Linux
             http://www.arm.linux.org.uk/personal/aboutme.html

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