+ selftests-vm-add-hugetlb_shared-userfaultfd-test-to-run_vmtestssh.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: selftests: vm: add hugetlb_shared userfaultfd test to run_vmtests.sh
has been added to the -mm mm-unstable branch.  Its filename is
     selftests-vm-add-hugetlb_shared-userfaultfd-test-to-run_vmtestssh.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-vm-add-hugetlb_shared-userfaultfd-test-to-run_vmtestssh.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Axel Rasmussen <axelrasmussen@google.com>
Subject: selftests: vm: add hugetlb_shared userfaultfd test to run_vmtests.sh
Date: Mon, 8 Aug 2022 10:56:10 -0700

Patch series "userfaultfd: add /dev/userfaultfd for fine grained access
control", v5.

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/20220719195628.3415852-1-axelrasmussen@google.com/
[2]: https://lore.kernel.org/lkml/686276b9-4530-2045-6bd8-170e5943abe4@schaufler-ca.com/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/20220808175614.3885028-1-axelrasmussen@google.com
Link: https://lkml.kernel.org/r/20220808175614.3885028-2-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dmitry V. Levin <ldv@altlinux.org>
Cc: Gleb Fotengauer-Malinovskiy <glebfm@altlinux.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/vm/run_vmtests.sh |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/tools/testing/selftests/vm/run_vmtests.sh~selftests-vm-add-hugetlb_shared-userfaultfd-test-to-run_vmtestssh
+++ a/tools/testing/selftests/vm/run_vmtests.sh
@@ -121,9 +121,11 @@ run_test ./gup_test -a
 run_test ./gup_test -ct -F 0x1 0 19 0x1000
 
 run_test ./userfaultfd anon 20 16
-# Test requires source and destination huge pages.  Size of source
-# (half_ufd_size_MB) is passed as argument to test.
+# Hugetlb tests require source and destination huge pages. Pass in half the
+# size ($half_ufd_size_MB), which is used for *each*.
 run_test ./userfaultfd hugetlb "$half_ufd_size_MB" 32
+run_test ./userfaultfd hugetlb_shared "$half_ufd_size_MB" 32 "$mnt"/uffd-test
+rm -f "$mnt"/uffd-test
 run_test ./userfaultfd shmem 20 16
 
 #cleanup
_

Patches currently in -mm which might be from axelrasmussen@google.com are

selftests-vm-add-hugetlb_shared-userfaultfd-test-to-run_vmtestssh.patch
userfaultfd-add-dev-userfaultfd-for-fine-grained-access-control.patch
userfaultfd-selftests-modify-selftest-to-use-dev-userfaultfd.patch
userfaultfd-update-documentation-to-describe-dev-userfaultfd.patch
selftests-vm-add-dev-userfaultfd-test-cases-to-run_vmtestssh.patch