Re: [PATCH v3 1/2] mm: Add an F_SEAL_FUTURE_WRITE seal to memfd

[valdis . kletnieks]

On Wed, 17 Oct 2018 23:59:07 -0700, "Joel Fernandes (Google)" said:
> This usecase cannot be implemented with the existing F_SEAL_WRITE seal.
> To support the usecase, this patch adds a new F_SEAL_FUTURE_WRITE seal
> which prevents any future mmap and write syscalls from succeeding while
> keeping the existing mmap active. The following program shows the seal
> working in action:

What is supposed to happen if some other process has an already existing R/W
mmap of the region?  (For that matter, the test program doesn't seem to
actually test that the existing mmap region remains writable?)

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