linux-kernel - Re: [PATCH] mremap: properly flush TLB before releasing the page

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Message-ID: <20181102152516.dkqpeubxh6c3phl2@kshutemo-mobl1>
Date:   Fri, 2 Nov 2018 18:25:16 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Jann Horn <jannh@...gle.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Will Deacon <will.deacon@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, kernel list <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux-MM <linux-mm@...ck.org>, Michal Hocko <mhocko@...nel.org>,
        Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH] mremap: properly flush TLB before releasing the page

On Fri, Nov 02, 2018 at 04:00:17PM +0100, Jann Horn wrote:
> On Fri, Nov 2, 2018 at 3:56 PM Kirill A. Shutemov <kirill@...temov.name> wrote:
> > On Fri, Nov 02, 2018 at 01:22:42PM +0000, Will Deacon wrote:
> > > From: Linus Torvalds <torvalds@...ux-foundation.org>
> > >
> > > Commit eb66ae030829605d61fbef1909ce310e29f78821 upstream.
> >
> > I have never seen the original patch on mailing lists, so I'll reply to
> > the backport.
> 
> For context, the original bug report is public at
> https://bugs.chromium.org/p/project-zero/issues/detail?id=1695 .

Okay. I see.

I wounder if it would be cheaper to fix this by taking i_mmap_lock_write()
unconditionally in mremap() path rather than do a lot of flushing.
We take the lock now only to remap to lower addresses.

-- 
 Kirill A. Shutemov