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From: Andrew Morton <akpm@linux-foundation.org>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: linux-kernel@vger.kernel.org,
	Nicolas Geoffray <ngeoffray@google.com>,
	kernel-team@android.com, Hugh Dickins <hughd@google.com>,
	linux-kselftest@vger.kernel.org, linux-mm@kvack.org,
	Shuah Khan <shuah@kernel.org>
Subject: Re: [PATCH 1/2] memfd: Fix COW issue on MAP_PRIVATE and F_SEAL_FUTURE_WRITE mappings
Date: Thu, 7 Nov 2019 19:25:28 -0800	[thread overview]
Message-ID: <20191107192528.0c22e8e122a04d4f8d29c5eb@linux-foundation.org> (raw)
In-Reply-To: <20191108020614.GA99567@google.com>

On Thu, 7 Nov 2019 21:06:14 -0500 Joel Fernandes <joel@joelfernandes.org> wrote:

> On Thu, Nov 07, 2019 at 05:00:23PM -0800, Andrew Morton wrote:
> > On Thu,  7 Nov 2019 14:53:54 -0500 "Joel Fernandes (Google)" <joel@joelfernandes.org> wrote:
> > 
> > > F_SEAL_FUTURE_WRITE has unexpected behavior when used with MAP_PRIVATE:
> > > A private mapping created after the memfd file that gets sealed with
> > > F_SEAL_FUTURE_WRITE loses the copy-on-write at fork behavior, meaning
> > > children and parent share the same memory, even though the mapping is
> > > private.
> > 
> > That sounds fairly serious.  Should this be backported into -stable kernels?
> 
> Yes, it should be.

I added

Fixes: ab3948f58ff84 ("mm/memfd: add an F_SEAL_FUTURE_WRITE seal to memfd")
Cc: <stable@vger.kernel.org>

> The F_SEAL_FUTURE_WRITE feature was introduced in v5.1 so
> v5.3.x stable kernels would need a backport. I can submit a backport tomorrow
> unless we are Ok with stable automatically picking it up (I believe the
> stable folks "auto select" fixes which should detect this is a fix since I
> have said it is a fix in the subject line).

The Cc:stable tag should trigger the appropriate actions, assisted by
the Fixes:.  I doubt if "fix" in the Subject has much effect.


  reply	other threads:[~2019-11-08  3:25 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-07 19:53 Joel Fernandes (Google)
2019-11-07 19:53 ` [PATCH 2/2] memfd: Add test for COW " Joel Fernandes (Google)
2019-11-08  1:00 ` [PATCH 1/2] memfd: Fix COW issue " Andrew Morton
2019-11-08  2:06   ` Joel Fernandes
2019-11-08  3:25     ` Andrew Morton [this message]
2019-11-08  6:37     ` Greg KH
2019-11-08 15:34       ` Joel Fernandes
2019-11-08  6:33 ` Christoph Hellwig
2019-11-08 15:35   ` Joel Fernandes

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