| From: |
| Florent Revest <revest-AT-chromium.org> |
| To: |
| linux-kernel-AT-vger.kernel.org, linux-mm-AT-kvack.org |
| Subject: |
| [PATCH v3 0/5] MDWE without inheritance |
| Date: |
| Tue, 04 Jul 2023 17:36:24 +0200 |
| Message-ID: |
| <20230704153630.1591122-1-revest@chromium.org> |
| Cc: |
| akpm-AT-linux-foundation.org, catalin.marinas-AT-arm.com, anshuman.khandual-AT-arm.com, joey.gouly-AT-arm.com, mhocko-AT-suse.com, keescook-AT-chromium.org, david-AT-redhat.com, peterx-AT-redhat.com, izbyshev-AT-ispras.ru, broonie-AT-kernel.org, szabolcs.nagy-AT-arm.com, kpsingh-AT-kernel.org, gthelen-AT-google.com, toiwoton-AT-gmail.com, Florent Revest <revest-AT-chromium.org> |
| Archive-link: |
| Article |
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.
This series applies on the mm-everything-2023-05-16-23-30 tag of the mm tree:
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/
Diff since v2:
- Turned the MMF_INIT_FLAGS macro into a mmf_init_flags function as suggested by
David Hildenbrand
- Removed the ability to transition from to PR_MDWE_REFUSE_EXEC_GAIN from
(PR_MDWE_REFUSE_EXEC_GAIN | PR_MDWE_NO_INHERIT) which also significantly
simplifies the prctl_set_mdwe logic
- Cc-ed -stable on patch 3 as suggested by Alexey Izbyshev
- Added a handful of Reviewed-by/Acked-by trailers
Diff since v1:
- MMF_HAS_MDWE_NO_INHERIT clears MMF_HAS_MDWE in the fork path as part of a
MMF_INIT_FLAGS macro (suggested by Catalin)
- PR_MDWE_* are defined as unsigned long rather than int (suggested by Andrey)
Florent Revest (5):
kselftest: vm: Fix tabs/spaces inconsistency in the mdwe test
kselftest: vm: Fix mdwe's mmap_FIXED test case
mm: Make PR_MDWE_REFUSE_EXEC_GAIN an unsigned long
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/sched/coredump.h | 10 +++
include/uapi/linux/prctl.h | 3 +-
kernel/fork.c | 2 +-
kernel/sys.c | 32 +++++--
tools/include/uapi/linux/prctl.h | 3 +-
tools/testing/selftests/mm/mdwe_test.c | 113 +++++++++++++++++++++----
6 files changed, 139 insertions(+), 24 deletions(-)
--
2.41.0.255.g8b1d071c50-goog
