[PATCH 3/3] selftests/mseal_system_mappings: Test vdso unmap and remap

[Chris Down]

Signed-off-by: Chris Down <chris@xxxxxxxxxxxxxx>
---
 .../mseal_system_mappings/sysmap_is_sealed.c  | 92 +++++++++++++++++++
 1 file changed, 92 insertions(+)

diff --git a/tools/testing/selftests/mseal_system_mappings/sysmap_is_sealed.c b/tools/testing/selftests/mseal_system_mappings/sysmap_is_sealed.c
index ea75ad537620..83b4fadfbfe7 100644
--- a/tools/testing/selftests/mseal_system_mappings/sysmap_is_sealed.c
+++ b/tools/testing/selftests/mseal_system_mappings/sysmap_is_sealed.c
@@ -10,6 +10,7 @@
 #include <unistd.h>
 #include <string.h>
 #include <stdbool.h>
+#include <sys/mman.h>
 #include <sys/utsname.h>
 #include <zlib.h>
 
@@ -232,4 +233,95 @@ TEST_F(basic, check_sealed)
 	EXPECT_EQ(expected, sealed);
 };
 
+static bool find_vdso(unsigned long *start, unsigned long *end)
+{
+	char line[MAX_LINE_LEN];
+	bool found = false;
+	FILE *maps;
+
+	maps = fopen("/proc/self/maps", "r");
+	if (!maps)
+		return false;
+
+	while (fgets(line, sizeof(line), maps)) {
+		if (strstr(line, "[vdso]") &&
+		    sscanf(line, "%lx-%lx", start, end) == 2) {
+			found = true;
+			break;
+		}
+	}
+
+	fclose(maps);
+	return found;
+}
+
+static int vdso_is_sealed(void)
+{
+	int sealed = -1;
+	FILE *maps;
+
+	maps = fopen("/proc/self/smaps", "r");
+	if (!maps)
+		return -1;
+	if (has_mapping("[vdso]", maps))
+		sealed = mapping_is_sealed(maps);
+	fclose(maps);
+	return sealed;
+}
+
+/*
+ * Unmapping or moving [vdso] must fail with EPERM when it is sealed. When it
+ * is not sealed, it succeeds and leaves glibc with a stale vdso pointer, which
+ * is fine because each test runs in its own forked child.
+ */
+TEST(vdso_munmap)
+{
+	int sealed;
+	unsigned long start, end;
+	int ret;
+
+	if (!find_vdso(&start, &end))
+		SKIP(return, "could not find the mapping, [vdso]");
+	sealed = vdso_is_sealed();
+	if (sealed < 0)
+		SKIP(return, "could not read the [vdso] sealing state");
+
+	ret = munmap((void *)start, end - start);
+	if (sealed) {
+		EXPECT_EQ(-1, ret);
+		EXPECT_EQ(EPERM, errno);
+	} else {
+		EXPECT_EQ(0, ret);
+	}
+	EXPECT_EQ(sealed, find_vdso(&start, &end));
+}
+
+TEST(vdso_mremap)
+{
+	int sealed;
+	unsigned long start, end, size, new_start;
+	void *dst, *ret;
+
+	if (!find_vdso(&start, &end))
+		SKIP(return, "could not find the mapping, [vdso]");
+	sealed = vdso_is_sealed();
+	if (sealed < 0)
+		SKIP(return, "could not read the [vdso] sealing state");
+	size = end - start;
+
+	dst = mmap(NULL, size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	ASSERT_NE(MAP_FAILED, dst);
+
+	ret = mremap((void *)start, size, size, MREMAP_MAYMOVE | MREMAP_FIXED,
+		     dst);
+	if (sealed) {
+		EXPECT_EQ(MAP_FAILED, ret);
+		EXPECT_EQ(EPERM, errno);
+	} else {
+		EXPECT_EQ(dst, ret);
+	}
+	ASSERT_TRUE(find_vdso(&new_start, &end));
+	EXPECT_EQ(sealed ? start : (unsigned long)dst, new_start);
+}
+
 TEST_HARNESS_MAIN
-- 
2.54.0