selftests/harness: remove use of LINE_MAX

Android was seeing a compliation error because its C library does not
define LINE_MAX. This replaces the use of LINE_MAX / snprintf with
asprintf, which will change the behavior to not truncate the test name if
it is over 2048 chars long.

See also:
https://github.com/llvm/llvm-project/issues/88119

[akpm@linux-foundation.org: remove limits.h include, per Edward]
[akpm@linux-foundation.org: check asprintf() return]
[usama.anjum@collabora.com: fix undeclared function error]
Link: https://lkml.kernel.org/r/20240417075530.3807625-1-usama.anjum@collabora.com
Link: https://lkml.kernel.org/r/20240411231954.62156-1-edliaw@google.com
Fixes: 38c957f07038 ("selftests: kselftest_harness: generate test name once")
Signed-off-by: Edward Liaw <edliaw@google.com>
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Bill Wendling <morbo@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Edward Liaw <edliaw@google.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: "Mike Rapoport (IBM)" <rppt@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Will Drewry <wad@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

kselftest: vm: add tests for no-inherit memory-deny-write-execute

Add some tests to cover the new PR_MDWE_NO_INHERIT flag of the
PR_SET_MDWE prctl.

Check that:
- it can't be set without PR_SET_MDWE
- MDWE flags can't be unset
- when set, PR_SET_MDWE doesn't propagate to children

Link: https://lkml.kernel.org/r/20230828150858.393570-7-revest@chromium.org
Signed-off-by: Florent Revest <revest@chromium.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Alexey Izbyshev <izbyshev@ispras.ru>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ayush Jain <ayush.jain3@amd.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Szabolcs Nagy <Szabolcs.Nagy@arm.com>
Cc: Topi Miettinen <toiwoton@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

kselftest: vm: check errnos in mdwe_test

Invalid prctls return a negative code and set errno. It's good practice
to check that errno is set as expected.

Link: https://lkml.kernel.org/r/20230828150858.393570-4-revest@chromium.org
Signed-off-by: Florent Revest <revest@chromium.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Alexey Izbyshev <izbyshev@ispras.ru>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ayush Jain <ayush.jain3@amd.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Szabolcs Nagy <Szabolcs.Nagy@arm.com>
Cc: Topi Miettinen <toiwoton@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

kselftest: vm: fix mdwe's mmap_FIXED test case

I checked with the original author, the mmap_FIXED test case wasn't
properly tested and fails. Currently, it maps two consecutive (non
overlapping) pages and expects the second mapping to be denied by MDWE but
these two pages have nothing to do with each other so MDWE is actually out
of the picture here.

What the test actually intended to do was to remap a virtual address using
MAP_FIXED. However, this operation unmaps the existing mapping and
creates a new one so the va is backed by a new page and MDWE is again out
of the picture, all remappings should succeed.

This patch keeps the test case to make it clear that this situation is
expected to work: MDWE shouldn't block a MAP_FIXED replacement.

Link: https://lkml.kernel.org/r/20230828150858.393570-3-revest@chromium.org
Fixes: 4cf1fe34fd18 ("kselftest: vm: add tests for memory-deny-write-execute")
Signed-off-by: Florent Revest <revest@chromium.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Tested-by: Ryan Roberts <ryan.roberts@arm.com>
Tested-by: Ayush Jain <ayush.jain3@amd.com>
Cc: Alexey Izbyshev <izbyshev@ispras.ru>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Szabolcs Nagy <Szabolcs.Nagy@arm.com>
Cc: Topi Miettinen <toiwoton@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

kselftest: vm: fix tabs/spaces inconsistency in the mdwe test

Patch series "MDWE without inheritance", v4.

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.

The background for this was discussed in these threads:
v1: https://lore.kernel.org/all/66900d0ad42797a55259061f757beece@ispras.ru/
v2: https://lore.kernel.org/all/d7e3749c-a718-df94-92af-1cb0fecab772@redhat.com/


This patch (of 6):

Fix tabs/spaces inconsistency in the mdwe test.

Link: https://lkml.kernel.org/r/20230828150858.393570-1-revest@chromium.org
Link: https://lkml.kernel.org/r/20230828150858.393570-2-revest@chromium.org
Signed-off-by: Florent Revest <revest@chromium.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Alexey Izbyshev <izbyshev@ispras.ru>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ayush Jain <ayush.jain3@amd.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Szabolcs Nagy <Szabolcs.Nagy@arm.com>
Cc: Topi Miettinen <toiwoton@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

kselftest: vm: fix unused variable warning

Remove unused variable from the MDWE test.

[joey.gouly@arm.com: add commit message]
Link: https://lkml.kernel.org/r/20230308190423.46491-4-joey.gouly@arm.com
Fixes: 4cf1fe34fd18 ("kselftest: vm: add tests for memory-deny-write-execute")
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Alexey Izbyshev <izbyshev@ispras.ru>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: nd <nd@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

kselftest: vm: add tests for memory-deny-write-execute

Add some tests to cover the new PR_SET_MDWE prctl.

Link: https://lkml.kernel.org/r/20230119160344.54358-3-joey.gouly@arm.com
Co-developed-by: Joey Gouly <joey.gouly@arm.com>
Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Jeremy Linton <jeremy.linton@arm.com>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Mark Brown <broonie@kernel.org>
Cc: nd <nd@arm.com>
Cc: Szabolcs Nagy <szabolcs.nagy@arm.com>
Cc: Topi Miettinen <toiwoton@gmail.com>
Cc: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>