Re: [PATCH 2/6] freepgt2: sys_mincore ignore FIRST_USER_PGD_NR

[Nick Piggin]

David Howells wrote:
> Hugh Dickins <hugh@xxxxxxxxxxx> wrote:
>
>
> > Remove use of FIRST_USER_PGD_NR from sys_mincore: it's inconsistent (no
> > other syscall refers to it), unnecessary (sys_mincore loops over vmas
> > further down) and incorrect (misses user addresses in ARM's first pgd).
>
>
> You should make it use FIRST_USER_ADDRESS instead. This check allows NULL
> pointers and suchlike to be weeded out before having to take the semaphore.

I'm not sure whether it is worth keeping the singular special
case here to slightly speed up what would probably be a bug in
a userspace program.

--
SUSE Labs, Novell Inc.

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