Re: copy_to_user to a kmapped address

Russell King (rmk@arm.linux.org.uk)
Mon, 26 Aug 2002 21:33:04 +0100

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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