selftests: link libasan statically for tests with -fsanitize=address

When dynamically linking, Address Sanitizer requires its library to be the
first one to be loaded; this is apparently to ensure that every call to
malloc is intercepted. If using LD_PRELOAD, those listed libraries will
be loaded before the libraries listed in the program's ELF and will
therefore violate this requirement, leading to the below failure and
output from ASan.

commit 58e2847ad2e6 ("selftests: line buffer test program's stdout")
modified the kselftest runner to force line buffering by forcing the test
programs to run through `stdbuf`. It turns out that stdbuf implements
line buffering by injecting a library via LD_PRELOAD. Therefore selftests
that use ASan started failing.

Fix this by statically linking libasan in the affected test programs,
using the `-static-libasan` option. Note this is already the default for
Clang, but not got GCC.

Test output sample for failing case:

TAP version 13
1..3
# timeout set to 300
# selftests: openat2: openat2_test
# ==4052==ASan runtime does not come first in initial library list;
you should either link runtime to your application or manually preload
it with LD_PRELOAD.
not ok 1 selftests: openat2: openat2_test # exit=1
# timeout set to 300
# selftests: openat2: resolve_test
# ==4070==ASan runtime does not come first in initial library list;
you should either link runtime to your application or manually preload
it with LD_PRELOAD.
not ok 2 selftests: openat2: resolve_test # exit=1

Link: https://lkml.kernel.org/r/20230912135048.1755771-1-ryan.roberts@arm.com
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Fixes: 58e2847ad2e6 ("selftests: line buffer test program's stdout")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202309121342.97e2f008-oliver.sang@intel.com
Cc: David Hildenbrand <david@redhat.com>
Cc: Florent Revest <revest@chromium.org>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tom Rix <trix@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

selftests: openat2: Add missing dependency in Makefile

Add a dependency on header helpers.h to the main target; while at that add
to helpers.h also a missing include for bool types.

Cc: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

selftests: add openat2(2) selftests

Test all of the various openat2(2) flags. A small stress-test of a
symlink-rename attack is included to show that the protections against
".."-based attacks are sufficient.

The main things these self-tests are enforcing are:

* The struct+usize ABI for openat2(2) and copy_struct_from_user() to
ensure that upgrades will be handled gracefully (in addition,
ensuring that misaligned structures are also handled correctly).

* The -EINVAL checks for openat2(2) are all correctly handled to avoid
userspace passing unknown or conflicting flag sets (most
importantly, ensuring that invalid flag combinations are checked).

* All of the RESOLVE_* semantics (including errno values) are
correctly handled with various combinations of paths and flags.

* RESOLVE_IN_ROOT correctly protects against the symlink rename(2)
attack that has been responsible for several CVEs (and likely will
be responsible for several more).

Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>