[PATCH V4 29/31] selftests/sgx: Test invalid access to removed enclave page

[Reinette Chatre]

Removing a page from an initialized enclave involves three steps:
(1) the user requests changing the page type to SGX_PAGE_TYPE_TRIM
via the SGX_IOC_ENCLAVE_MODIFY_TYPES  ioctl(), (2) on success the
ENCLU[EACCEPT] instruction is run from within the enclave to accept
the page removal, (3) the user initiates the actual removal of the
page via the SGX_IOC_ENCLAVE_REMOVE_PAGES ioctl().

Test two possible invalid accesses during the page removal flow:
* Test the behavior when a request to remove the page by changing its
  type to SGX_PAGE_TYPE_TRIM completes successfully but instead of
  executing ENCLU[EACCEPT] from within the enclave the enclave attempts
  to read from the page. Even though the page is accessible from the
  page table entries its type is SGX_PAGE_TYPE_TRIM and thus not
  accessible according to SGX. The expected behavior is a page fault
  with the SGX flag set in the error code.
* Test the behavior when the page type is changed successfully and
  ENCLU[EACCEPT] was run from within the enclave. The final ioctl(),
  SGX_IOC_ENCLAVE_REMOVE_PAGES, is omitted and replaced with an
  attempt to access the page. Even though the page is accessible
  from the page table entries its type is SGX_PAGE_TYPE_TRIM and
  thus not accessible according to SGX.  The expected behavior is
  a page fault with the SGX flag set in the error code.

Acked-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
Signed-off-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
---
Changes since V3:
- Add Jarkko's Acked-by tag.
- Rename SGX_IOC_ENCLAVE_MODIFY_TYPE to
  SGX_IOC_ENCLAVE_MODIFY_TYPES. (Jarkko)
- User provides just page type to SGX_IOC_ENCLAVE_MODIFY_TYPES ioctl(),
  replacing secinfo. (Jarkko)
- Let the SKIP() call involving SGX_IOC_ENCLAVE_MODIFY_TYPES span
  two lines to address checkpatch.pl warning triggered by new longer
  name.

Changes since V2:
- Rename struct sgx_enclave_modt -> struct sgx_enclave_modify_type

Changes since V1:
- Update to support ioctl() name change (SGX_IOC_PAGE_MODT ->
  SGX_IOC_ENCLAVE_MODIFY_TYPE) and provide secinfo as parameter instead
  of just page type (Jarkko).
- Use ioctl() instead of ioctl (Dave).

 tools/testing/selftests/sgx/main.c | 243 +++++++++++++++++++++++++++++
 1 file changed, 243 insertions(+)

diff --git a/tools/testing/selftests/sgx/main.c b/tools/testing/selftests/sgx/main.c
index fc72b04ce2a8..ba1c6c4b5ff2 100644
--- a/tools/testing/selftests/sgx/main.c
+++ b/tools/testing/selftests/sgx/main.c
@@ -1547,4 +1547,247 @@ TEST_F(enclave, remove_added_page_no_eaccept)
 	EXPECT_EQ(remove_ioc.count, 0);
 }
 
+/*
+ * Request enclave page removal but instead of correctly following with
+ * EACCEPT a read attempt to page is made from within the enclave.
+ */
+TEST_F(enclave, remove_added_page_invalid_access)
+{
+	struct encl_op_get_from_addr get_addr_op;
+	struct encl_op_put_to_addr put_addr_op;
+	struct sgx_enclave_modify_type ioc;
+	unsigned long data_start;
+	int ret, errno_save;
+
+	ASSERT_TRUE(setup_test_encl(ENCL_HEAP_SIZE_DEFAULT, &self->encl, _metadata));
+
+	memset(&self->run, 0, sizeof(self->run));
+	self->run.tcs = self->encl.encl_base;
+
+	/*
+	 * Hardware (SGX2) and kernel support is needed for this test. Start
+	 * with check that test has a chance of succeeding.
+	 */
+	memset(&ioc, 0, sizeof(ioc));
+	ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_MODIFY_TYPES, &ioc);
+
+	if (ret == -1) {
+		if (errno == ENOTTY)
+			SKIP(return,
+			     "Kernel does not support SGX_IOC_ENCLAVE_MODIFY_TYPES ioctl()");
+		else if (errno == ENODEV)
+			SKIP(return, "System does not support SGX2");
+	}
+
+	/*
+	 * Invalid parameters were provided during sanity check,
+	 * expect command to fail.
+	 */
+	EXPECT_EQ(ret, -1);
+
+	/*
+	 * Page that will be removed is the second data page in the .data
+	 * segment. This forms part of the local encl_buffer within the
+	 * enclave.
+	 */
+	data_start = self->encl.encl_base +
+		     encl_get_data_offset(&self->encl) + PAGE_SIZE;
+
+	/*
+	 * Sanity check that page at @data_start is writable before
+	 * removing it.
+	 *
+	 * Start by writing MAGIC to test page.
+	 */
+	put_addr_op.value = MAGIC;
+	put_addr_op.addr = data_start;
+	put_addr_op.header.type = ENCL_OP_PUT_TO_ADDRESS;
+
+	EXPECT_EQ(ENCL_CALL(&put_addr_op, &self->run, true), 0);
+
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.exception_vector, 0);
+	EXPECT_EQ(self->run.exception_error_code, 0);
+	EXPECT_EQ(self->run.exception_addr, 0);
+
+	/*
+	 * Read memory that was just written to, confirming that data
+	 * previously written (MAGIC) is present.
+	 */
+	get_addr_op.value = 0;
+	get_addr_op.addr = data_start;
+	get_addr_op.header.type = ENCL_OP_GET_FROM_ADDRESS;
+
+	EXPECT_EQ(ENCL_CALL(&get_addr_op, &self->run, true), 0);
+
+	EXPECT_EQ(get_addr_op.value, MAGIC);
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.exception_vector, 0);
+	EXPECT_EQ(self->run.exception_error_code, 0);
+	EXPECT_EQ(self->run.exception_addr, 0);
+
+	/* Start page removal by requesting change of page type to PT_TRIM. */
+	memset(&ioc, 0, sizeof(ioc));
+
+	ioc.offset = encl_get_data_offset(&self->encl) + PAGE_SIZE;
+	ioc.length = PAGE_SIZE;
+	ioc.page_type = SGX_PAGE_TYPE_TRIM;
+
+	ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_MODIFY_TYPES, &ioc);
+	errno_save = ret == -1 ? errno : 0;
+
+	EXPECT_EQ(ret, 0);
+	EXPECT_EQ(errno_save, 0);
+	EXPECT_EQ(ioc.result, 0);
+	EXPECT_EQ(ioc.count, 4096);
+
+	/*
+	 * Read from page that was just removed.
+	 */
+	get_addr_op.value = 0;
+
+	EXPECT_EQ(ENCL_CALL(&get_addr_op, &self->run, true), 0);
+
+	/*
+	 * From kernel perspective the page is present but according to SGX the
+	 * page should not be accessible so a #PF with SGX bit set is
+	 * expected.
+	 */
+
+	EXPECT_EQ(self->run.function, ERESUME);
+	EXPECT_EQ(self->run.exception_vector, 14);
+	EXPECT_EQ(self->run.exception_error_code, 0x8005);
+	EXPECT_EQ(self->run.exception_addr, data_start);
+}
+
+/*
+ * Request enclave page removal and correctly follow with
+ * EACCEPT but do not follow with removal ioctl() but instead a read attempt
+ * to removed page is made from within the enclave.
+ */
+TEST_F(enclave, remove_added_page_invalid_access_after_eaccept)
+{
+	struct encl_op_get_from_addr get_addr_op;
+	struct encl_op_put_to_addr put_addr_op;
+	struct sgx_enclave_modify_type ioc;
+	struct encl_op_eaccept eaccept_op;
+	unsigned long data_start;
+	int ret, errno_save;
+
+	ASSERT_TRUE(setup_test_encl(ENCL_HEAP_SIZE_DEFAULT, &self->encl, _metadata));
+
+	memset(&self->run, 0, sizeof(self->run));
+	self->run.tcs = self->encl.encl_base;
+
+	/*
+	 * Hardware (SGX2) and kernel support is needed for this test. Start
+	 * with check that test has a chance of succeeding.
+	 */
+	memset(&ioc, 0, sizeof(ioc));
+	ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_MODIFY_TYPES, &ioc);
+
+	if (ret == -1) {
+		if (errno == ENOTTY)
+			SKIP(return,
+			     "Kernel does not support SGX_IOC_ENCLAVE_MODIFY_TYPES ioctl()");
+		else if (errno == ENODEV)
+			SKIP(return, "System does not support SGX2");
+	}
+
+	/*
+	 * Invalid parameters were provided during sanity check,
+	 * expect command to fail.
+	 */
+	EXPECT_EQ(ret, -1);
+
+	/*
+	 * Page that will be removed is the second data page in the .data
+	 * segment. This forms part of the local encl_buffer within the
+	 * enclave.
+	 */
+	data_start = self->encl.encl_base +
+		     encl_get_data_offset(&self->encl) + PAGE_SIZE;
+
+	/*
+	 * Sanity check that page at @data_start is writable before
+	 * removing it.
+	 *
+	 * Start by writing MAGIC to test page.
+	 */
+	put_addr_op.value = MAGIC;
+	put_addr_op.addr = data_start;
+	put_addr_op.header.type = ENCL_OP_PUT_TO_ADDRESS;
+
+	EXPECT_EQ(ENCL_CALL(&put_addr_op, &self->run, true), 0);
+
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.exception_vector, 0);
+	EXPECT_EQ(self->run.exception_error_code, 0);
+	EXPECT_EQ(self->run.exception_addr, 0);
+
+	/*
+	 * Read memory that was just written to, confirming that data
+	 * previously written (MAGIC) is present.
+	 */
+	get_addr_op.value = 0;
+	get_addr_op.addr = data_start;
+	get_addr_op.header.type = ENCL_OP_GET_FROM_ADDRESS;
+
+	EXPECT_EQ(ENCL_CALL(&get_addr_op, &self->run, true), 0);
+
+	EXPECT_EQ(get_addr_op.value, MAGIC);
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.exception_vector, 0);
+	EXPECT_EQ(self->run.exception_error_code, 0);
+	EXPECT_EQ(self->run.exception_addr, 0);
+
+	/* Start page removal by requesting change of page type to PT_TRIM. */
+	memset(&ioc, 0, sizeof(ioc));
+
+	ioc.offset = encl_get_data_offset(&self->encl) + PAGE_SIZE;
+	ioc.length = PAGE_SIZE;
+	ioc.page_type = SGX_PAGE_TYPE_TRIM;
+
+	ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_MODIFY_TYPES, &ioc);
+	errno_save = ret == -1 ? errno : 0;
+
+	EXPECT_EQ(ret, 0);
+	EXPECT_EQ(errno_save, 0);
+	EXPECT_EQ(ioc.result, 0);
+	EXPECT_EQ(ioc.count, 4096);
+
+	eaccept_op.epc_addr = (unsigned long)data_start;
+	eaccept_op.ret = 0;
+	eaccept_op.flags = SGX_SECINFO_TRIM | SGX_SECINFO_MODIFIED;
+	eaccept_op.header.type = ENCL_OP_EACCEPT;
+
+	EXPECT_EQ(ENCL_CALL(&eaccept_op, &self->run, true), 0);
+
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.exception_vector, 0);
+	EXPECT_EQ(self->run.exception_error_code, 0);
+	EXPECT_EQ(self->run.exception_addr, 0);
+	EXPECT_EQ(eaccept_op.ret, 0);
+
+	/* Skip ioctl() to remove page. */
+
+	/*
+	 * Read from page that was just removed.
+	 */
+	get_addr_op.value = 0;
+
+	EXPECT_EQ(ENCL_CALL(&get_addr_op, &self->run, true), 0);
+
+	/*
+	 * From kernel perspective the page is present but according to SGX the
+	 * page should not be accessible so a #PF with SGX bit set is
+	 * expected.
+	 */
+
+	EXPECT_EQ(self->run.function, ERESUME);
+	EXPECT_EQ(self->run.exception_vector, 14);
+	EXPECT_EQ(self->run.exception_error_code, 0x8005);
+	EXPECT_EQ(self->run.exception_addr, data_start);
+}
+
 TEST_HARNESS_MAIN
-- 
2.25.1