Date: Fri, 10 Jul 2015 14:52:12 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>, Hugh Dickins <hughd@google.com>,
        Kirill Shutemov <kirill.shutemov@linux.intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Pavel Emelyanov <xemul@parallels.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 0/3] special_mapping_fault() is broken
Message-Id: <20150710145212.4440052265c4f6e074d1f391@linux-foundation.org>
In-Reply-To: <20150710165121.GA10341@redhat.com>
References: <20150710165121.GA10341@redhat.com>
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On Fri, 10 Jul 2015 18:51:21 +0200 Oleg Nesterov <oleg@redhat.com> wrote:

> special_mapping_fault() is absolutely broken. It seems it was always
> wrong, but this didn't matter until vdso/vvar started to use more than
> one page.
> 
> The patches are the same, just 1/3 was re-diffed on top of the recent
> 6b7339f4c31ad "mm: avoid setting up anonymous pages into file mapping"
> from Kirill.
> 
> And after this change vma_is_anonymous() becomes really trivial, it
> simply checks vm_ops == NULL. However, I do think the helper makes
> sense. There are a lot of ->vm_ops != NULL checks, the helper makes
> the caller's code more understandable (self-documented) and this is
> more grep-friendly.

I'm trying to work out which kernel version(s) this should go into,
without a lot of success.

What do we think the worst-case effects of the bug?
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