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    SubjectRe: x86-cache-pollution-aware-__copy_from_user_ll.patch added to -mm tree
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    From: Dave Jones <davej@redhat.com>
    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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