[PATCH] munmap sealed memory cause memory to split (bug)

[jeffxu]

From: Jeff Xu <jef...@google.com>

It appears there is a regression on the latest mm,
when munmap sealed memory, it can cause unexpected VMA split.
E.g. repro use this test.
---
 tools/testing/selftests/mm/mseal_test.c | 76 +++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/tools/testing/selftests/mm/mseal_test.c 
b/tools/testing/selftests/mm/mseal_test.c
index fa74dbe4a684..0af33e13b606 100644
--- a/tools/testing/selftests/mm/mseal_test.c
+++ b/tools/testing/selftests/mm/mseal_test.c
@@ -1969,6 +1969,79 @@ static void test_madvise_filebacked_was_writable(bool 
seal)
        REPORT_TEST_PASS();
 }
 
+static void test_munmap_free_multiple_ranges_with_split(bool seal)
+{
+       void *ptr;
+       unsigned long page_size = getpagesize();
+       unsigned long size = 12 * page_size;
+       int ret;
+       int prot;
+
+       setup_single_address(size, &ptr);
+       FAIL_TEST_IF_FALSE(ptr != (void *)-1);
+
+       /* seal the middle 4 page */
+       if (seal) {
+               ret = sys_mseal(ptr + 4 * page_size, 4 * page_size);
+               FAIL_TEST_IF_FALSE(!ret);
+
+               size = get_vma_size(ptr, &prot);
+               FAIL_TEST_IF_FALSE(size == 4 * page_size);
+               FAIL_TEST_IF_FALSE(prot == 4);
+
+               size = get_vma_size(ptr +  4 * page_size, &prot);
+               FAIL_TEST_IF_FALSE(size == 4 * page_size);
+               FAIL_TEST_IF_FALSE(prot == 4);
+
+               size = get_vma_size(ptr +  8 * page_size, &prot);
+               FAIL_TEST_IF_FALSE(size == 4 * page_size);
+               FAIL_TEST_IF_FALSE(prot == 4);
+       }
+
+       /* munmap 4  pages from the third page */
+       ret = sys_munmap(ptr + 2 * page_size, 4 * page_size);
+       if (seal) {
+               FAIL_TEST_IF_FALSE(ret);
+               FAIL_TEST_IF_FALSE(errno == EPERM);
+
+               size = get_vma_size(ptr, &prot);
+               FAIL_TEST_IF_FALSE(size == 4 * page_size);
+               FAIL_TEST_IF_FALSE(prot == 4);
+
+               size = get_vma_size(ptr +  4 * page_size, &prot);
+               FAIL_TEST_IF_FALSE(size == 4 * page_size);
+               FAIL_TEST_IF_FALSE(prot == 4);
+
+               size = get_vma_size(ptr +  8 * page_size, &prot);
+               FAIL_TEST_IF_FALSE(size == 4 * page_size);
+               FAIL_TEST_IF_FALSE(prot == 4);
+       } else
+               FAIL_TEST_IF_FALSE(!ret);
+
+       /* munmap 4 pages from the sealed page */
+       ret = sys_munmap(ptr + 6 * page_size, 4 * page_size);
+       if (seal) {
+               FAIL_TEST_IF_FALSE(ret);
+               FAIL_TEST_IF_FALSE(errno == EPERM);
+
+               size = get_vma_size(ptr + 4 * page_size, &prot);
+               FAIL_TEST_IF_FALSE(size == 4 * page_size);
+               FAIL_TEST_IF_FALSE(prot == 4);
+
+               size = get_vma_size(ptr +  4 * page_size, &prot);
+               FAIL_TEST_IF_FALSE(size == 4 * page_size);
+               FAIL_TEST_IF_FALSE(prot == 4);
+
+               size = get_vma_size(ptr +  8 * page_size, &prot);
+               FAIL_TEST_IF_FALSE(size == 4 * page_size);
+               FAIL_TEST_IF_FALSE(prot == 4);
+       } else
+               FAIL_TEST_IF_FALSE(!ret);
+
+       REPORT_TEST_PASS();
+}
+
+
 int main(int argc, char **argv)
 {
        bool test_seal = seal_support();
@@ -2099,5 +2172,8 @@ int main(int argc, char **argv)
        test_madvise_filebacked_was_writable(false);
        test_madvise_filebacked_was_writable(true);
 
+       test_munmap_free_multiple_ranges_with_split(false);
+       test_munmap_free_multiple_ranges_with_split(true);
+
        ksft_finished();
 }
-- 
2.47.0.rc1.288.g06298d1525-goog