linux-kernel - [PATCH 0/4] MDWE without inheritance

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Message-ID: <20230504170942.822147-1-revest@chromium.org>
Date:   Thu,  4 May 2023 19:09:38 +0200
From:   Florent Revest <revest@...omium.org>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     akpm@...ux-foundation.org, catalin.marinas@....com,
        anshuman.khandual@....com, joey.gouly@....com, mhocko@...e.com,
        keescook@...omium.org, david@...hat.com, peterx@...hat.com,
        izbyshev@...ras.ru, nd@....com, broonie@...nel.org,
        szabolcs.nagy@....com, Florent Revest <revest@...omium.org>
Subject: [PATCH 0/4] MDWE without inheritance

Joey recently introduced a Memory-Deny-Write-Executable (MDWE) prctl which tags
current with a flag that prevents pages that were previously not executable from
becoming executable.
This tag always gets inherited by children tasks. (it's in MMF_INIT_MASK)

At Google, we've been using a somewhat similar downstream patch for a few years
now. To make the adoption of this feature easier, we've had it support a mode in
which the W^X flag does not propagate to children. For example, this is handy if
a C process which wants W^X protection suspects it could start children
processes that would use a JIT.

I'd like to align our features with the upstream prctl. This series proposes a
new NO_INHERIT flag to the MDWE prctl to make this kind of adoption easier. It
sets a different flag in current that is not in MMF_INIT_MASK and which does not
propagate.

As part of looking into MDWE, I also fixed a couple of things in the MDWE test.

Florent Revest (4):
  kselftest: vm: Fix tabs/spaces inconsistency in the mdwe test
  kselftest: vm: Fix mdwe's mmap_FIXED test case
  mm: Add a NO_INHERIT flag to the PR_SET_MDWE prctl
  kselftest: vm: Add tests for no-inherit memory-deny-write-execute

 include/linux/mman.h                   |   8 +-
 include/linux/sched/coredump.h         |   1 +
 include/uapi/linux/prctl.h             |   1 +
 kernel/sys.c                           |  29 +++++--
 tools/include/uapi/linux/prctl.h       |   1 +
 tools/testing/selftests/mm/mdwe_test.c | 110 +++++++++++++++++++++----
 6 files changed, 128 insertions(+), 22 deletions(-)

-- 
2.40.1.495.gc816e09b53d-goog