selftests/sgx: Test faulty enclave behavior

Removing a page from an initialized enclave involves three steps:
first the user requests changing the page type to SGX_PAGE_TYPE_TRIM
via an ioctl(), on success the ENCLU[EACCEPT] instruction needs to be
run from within the enclave to accept the page removal, finally the
user requests page removal to be completed via an ioctl(). Only after
acceptance (ENCLU[EACCEPT]) from within the enclave can the kernel
remove the page from a running enclave.

Test the behavior when the user's request to change the page type
succeeds, but the ENCLU[EACCEPT] instruction is not run before the
ioctl() requesting page removal is run. This should not be permitted.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lkml.kernel.org/r/fa5da30ebac108b7517194c3038b52995602b996.1652137848.git.reinette.chatre@intel.com

Author: rchatre

tools/testing/selftests/sgx/main.c

@@ -1433,4 +1433,118 @@ TEST_F(enclave, tcs_create)
 	munmap(addr, 3 * PAGE_SIZE);
 }
 
+/*
+ * Ensure sane behavior if user requests page removal, does not run
+ * EACCEPT from within enclave but still attempts to finalize page removal
+ * with the SGX_IOC_ENCLAVE_REMOVE_PAGES ioctl(). The latter should fail
+ * because the removal was not EACCEPTed from within the enclave.
+ */
+TEST_F(enclave, remove_added_page_no_eaccept)
+{
+	struct sgx_enclave_remove_pages remove_ioc;
+	struct encl_op_get_from_addr get_addr_op;
+	struct sgx_enclave_modify_types modt_ioc;
+	struct encl_op_put_to_addr put_addr_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(&modt_ioc, 0, sizeof(modt_ioc));
+	ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_MODIFY_TYPES, &modt_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(&modt_ioc, 0, sizeof(modt_ioc));
+
+	modt_ioc.offset = encl_get_data_offset(&self->encl) + PAGE_SIZE;
+	modt_ioc.length = PAGE_SIZE;
+	modt_ioc.page_type = SGX_PAGE_TYPE_TRIM;
+
+	ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_MODIFY_TYPES, &modt_ioc);
+	errno_save = ret == -1 ? errno : 0;
+
+	EXPECT_EQ(ret, 0);
+	EXPECT_EQ(errno_save, 0);
+	EXPECT_EQ(modt_ioc.result, 0);
+	EXPECT_EQ(modt_ioc.count, 4096);
+
+	/* Skip EACCEPT */
+
+	/* Send final ioctl() to complete page removal */
+	memset(&remove_ioc, 0, sizeof(remove_ioc));
+
+	remove_ioc.offset = encl_get_data_offset(&self->encl) + PAGE_SIZE;
+	remove_ioc.length = PAGE_SIZE;
+
+	ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_REMOVE_PAGES, &remove_ioc);
+	errno_save = ret == -1 ? errno : 0;
+
+	/* Operation not permitted since EACCEPT was omitted. */
+	EXPECT_EQ(ret, -1);
+	EXPECT_EQ(errno_save, EPERM);
+	EXPECT_EQ(remove_ioc.count, 0);
+}
+
 TEST_HARNESS_MAIN