Messages in this thread | | | Date | Thu, 7 Nov 2019 19:25:28 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH 1/2] memfd: Fix COW issue on MAP_PRIVATE and F_SEAL_FUTURE_WRITE mappings |
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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.
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