Re: x86-cache-pollution-aware-__copy_from_user_ll.patch added to-mm tree

[David S. Miller]

From: Dave Jones <davej@xxxxxxxxxx>
Subject: Re: x86-cache-pollution-aware-__copy_from_user_ll.patch added to -mm tree
Date: Sun, 4 Sep 2005 16:23:33 -0400

> On Sun, Sep 04, 2005 at 01:16:00PM -0700, Andrew Morton wrote:
>  >  unsigned long __copy_to_user_ll(void __user *to, const void *from, unsigned long n)
>  >  {
>  >  	BUG_ON((long) n < 0);
> 
> Ehh? It's unsigned. This will never be true.

It's to catch the user slipping in enormous lengths to
the user copy routines.

Sparc64 makes this check as well.  From U3memcpy.S:

	srlx		%o2, 31, %g2
	cmp		%g2, 0
	tne		%xcc, 5

%o2 is the length, we make sure the upper 33-bits are clear.
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