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

From: Christoph Hellwig
Date: Fri Nov 08 2019 - 01:33:13 EST


> - * Since the F_SEAL_FUTURE_WRITE seals allow for a MAP_SHARED
> - * read-only mapping, take care to not allow mprotect to revert
> - * protections.
> + * Since an F_SEAL_FUTURE_WRITE sealed memfd can be mapped as
> + * MAP_SHARED and read-only, take care to not allow mprotect to
> + * revert protections on such mappings. Do this only for shared
> + * mappings. For private mappings, don't need to mask VM_MAYWRITE

This adds an > 80 char line.