selftests: vm: add hugetlb_shared userfaultfd test to run_vmtests.sh

Patch series "userfaultfd: add /dev/userfaultfd for fine grained access
control", v7.

Why not ...?
============

- Why not /proc/[pid]/userfaultfd? Two main points (additional discussion [1]):

    - /proc/[pid]/* files are all owned by the user/group of the process, and
      they don't really support chmod/chown. So, without extending procfs it
      doesn't solve the problem this series is trying to solve.

    - The main argument *for* this was to support creating UFFDs for remote
      processes. But, that use case clearly calls for CAP_SYS_PTRACE, so to
      support this we could just use the UFFD syscall as-is.

- Why not use a syscall? Access to syscalls is generally controlled by
  capabilities. We don't have a capability which is used for userfaultfd access
  without also granting more / other permissions as well, and adding a new
  capability was rejected [2].

    - It's possible a LSM could be used to control access instead, but I have
      some concerns. I don't think this approach would be as easy to use,
      particularly if we were to try to solve this with something heavyweight
      like SELinux. Maybe we could pursue adding a new LSM specifically for
      this user case, but it may be too narrow of a case to justify that.

[1]: https://patchwork.kernel.org/project/linux-mm/cover/[email protected]/
[2]: https://lore.kernel.org/lkml/[email protected]/T/


This patch (of 5):

This not being included was just a simple oversight.  There are certain
features (like minor fault support) which are only enabled on shared
mappings, so without including hugetlb_shared we actually lose a
significant amount of test coverage.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Axel Rasmussen <[email protected]>
Reviewed-by: Shuah Khan <[email protected]>
Reviewed-by: Peter Xu <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Dmitry V. Levin <[email protected]>
Cc: Gleb Fotengauer-Malinovskiy <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Nadav Amit <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Zhang Yi <[email protected]>
Cc: Mike Rapoport <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions