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Date: Tue, 16 May 2017 22:33:48 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>,
        Kostya Serebryany <kcc@google.com>, Eric Dumazet <edumazet@google.com>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] [iov_iter] use memmove() when copying to/from user page
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On Tue, May 16, 2017 at 02:01:51PM -0700, Dmitry Vyukov wrote:

> > In that case your patch does not suffice.  Overlapping move _forwards_ still
> > yields unexpected results, doesn't it?
> 
> Why? memmove can move both ways. Do we need to change more memcpy's to
> memmove's?

Because it's not going to be *one* call of memcpy() or memmove().  It's
one per page.