Re: [PATCH 1/2] memfd: Fix COW issue on MAP_PRIVATE and F_SEAL_FUTURE_WRITE mappings

[Andrew Morton]

On Thu,  7 Nov 2019 14:53:54 -0500 "Joel Fernandes (Google)" <joel@xxxxxxxxxxxxxxxxx> 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?