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

[jeffxu]

From: Jeff Xu <jeffxu@xxxxxxxxxx>

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