linux-kernel - Re: [PATCH 0/3] special_mapping

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Message-ID: <20150621211951.GA18593@redhat.com>
Date:	Sun, 21 Jun 2015 23:19:51 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Hugh Dickins <hughd@...gle.com>,
	Jeff Moyer <jmoyer@...hat.com>,
	Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH 0/3] special_mapping_fault() is broken

Forgot to add Andy...

And forgot to mention. As for vdso in particular, I'd actually prefer
to make it have ->vm_file != NULL so that uprobe-in-vdso could work.
But this is not that simple, and I think these fixes (if correct) make
sense in any case, whatever we do with vdso.

On 06/21, Oleg Nesterov wrote:
>
> On 06/20, Oleg Nesterov wrote:
> >
> > Let me first send the changes which look "obviously correct" to me.
> > Perhaps I'll send more patches on top of this later.
>
> But lets also fix another unmap/remap bug before the cleanups...
> This series doesn't depend on the previous mremap fixes.
>
> 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.
>
> I am not sure about 1/3. As the changelog says the name is not very
> accurate, and I do not really like the vma->fault != NULL check. But
> I hope this can work, and we can change this helper later if needed.
>
> Please review.
>
> Oleg.
>
>  include/linux/mm.h |    5 +++++
>  mm/memory.c        |   13 ++++++-------
>  mm/mmap.c          |   14 +++-----------
>  3 files changed, 14 insertions(+), 18 deletions(-)

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