selftests/mm: add mseal test for no-discard madvise

Add an mseal test for madvise() operations that aren't considered
"discard" (e.g purely advisory ops such as MADV_RANDOM).

Link: https://lkml.kernel.org/r/20240807173336.2523757-3-pedro.falcato@gmail.com
Signed-off-by: Pedro Falcato <pedro.falcato@gmail.com>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/mm/mseal_test.c b/tools/testing/selftests/mm/mseal_test.c
index bfcea5cf9a48426cea4c84bca93f249ba3c45321..e70539c8bedecbf88c01f10193ee2ae3066a2aee 100644 (file)
--- a/tools/testing/selftests/mm/mseal_test.c
+++ b/tools/testing/selftests/mm/mseal_test.c
@@ -1720,6 +1720,38 @@ static void test_seal_discard_ro_anon(bool seal)
        REPORT_TEST_PASS();
 }
 
+static void test_seal_madvise_nodiscard(bool seal)
+{
+       void *ptr;
+       unsigned long page_size = getpagesize();
+       unsigned long size = 4 * page_size;
+       int ret;
+
+       setup_single_address(size, &ptr);
+       FAIL_TEST_IF_FALSE(ptr != (void *)-1);
+
+       if (seal) {
+               ret = seal_single_address(ptr, size);
+               FAIL_TEST_IF_FALSE(!ret);
+       }
+
+       /*
+        * Test a random madvise flag like MADV_RANDOM that does not touch page
+        * contents (and thus should work for msealed VMAs). RANDOM also happens to
+        * share bits with other discard-ish flags like REMOVE.
+        */
+       ret = sys_madvise(ptr, size, MADV_RANDOM);
+       FAIL_TEST_IF_FALSE(!ret);
+
+       ret = sys_munmap(ptr, size);
+       if (seal)
+               FAIL_TEST_IF_FALSE(ret < 0);
+       else
+               FAIL_TEST_IF_FALSE(!ret);
+
+       REPORT_TEST_PASS();
+}
+
 int main(int argc, char **argv)
 {
        bool test_seal = seal_support();
@@ -1811,6 +1843,8 @@ int main(int argc, char **argv)
        test_seal_mremap_move_fixed_zero(true);
        test_seal_mremap_move_dontunmap_anyaddr(false);
        test_seal_mremap_move_dontunmap_anyaddr(true);
+       test_seal_madvise_nodiscard(false);
+       test_seal_madvise_nodiscard(true);
        test_seal_discard_ro_anon(false);
        test_seal_discard_ro_anon(true);
        test_seal_discard_ro_anon_on_rw(false);