test: add firmware_class loader test

This provides a simple interface to trigger the firmware_class loader
to test built-in, filesystem, and user helper modes. Additionally adds
tests via the new interface to the selftests tree.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 131 insertions, 0 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 7a638aa3545b..213cd9f7e957 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1649,6 +1649,19 @@ config TEST_BPF
 
           If unsure, say N.
 
+config TEST_FIRMWARE
+        tristate "Test firmware loading via userspace interface"
+        default n
+        depends on FW_LOADER
+        help
+          This builds the "test_firmware" module that creates a userspace
+          interface for testing firmware loading. This can be used to
+          control the triggering of firmware loading without needing an
+          actual firmware-using device. The contents can be rechecked by
+          userspace.
+
+          If unsure, say N.
+
 source "samples/Kconfig"
 
 source "lib/Kconfig.kgdb"
diff --git a/lib/Makefile b/lib/Makefile
index ba967a19edba..230b4b1456d6 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_TEST_KSTRTOX) += test-kstrtox.o
 obj-$(CONFIG_TEST_MODULE) += test_module.o
 obj-$(CONFIG_TEST_USER_COPY) += test_user_copy.o
 obj-$(CONFIG_TEST_BPF) += test_bpf.o
+obj-$(CONFIG_TEST_FIRMWARE) += test_firmware.o
 
 ifeq ($(CONFIG_DEBUG_KOBJECT),y)
 CFLAGS_kobject.o += -DDEBUG
diff --git a/lib/test_firmware.c b/lib/test_firmware.c
new file mode 100644
index 000000000000..86374c1c49a4
--- /dev/null
+++ b/lib/test_firmware.c
@@ -0,0 +1,117 @@
+/*
+ * This module provides an interface to trigger and test firmware loading.
+ *
+ * It is designed to be used for basic evaluation of the firmware loading
+ * subsystem (for example when validating firmware verification). It lacks
+ * any extra dependencies, and will not normally be loaded by the system
+ * unless explicitly requested by name.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/firmware.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+static DEFINE_MUTEX(test_fw_mutex);
+static const struct firmware *test_firmware;
+
+static ssize_t test_fw_misc_read(struct file *f, char __user *buf,
+                                 size_t size, loff_t *offset)
+{
+        ssize_t rc = 0;
+
+        mutex_lock(&test_fw_mutex);
+        if (test_firmware)
+                rc = simple_read_from_buffer(buf, size, offset,
+                                             test_firmware->data,
+                                             test_firmware->size);
+        mutex_unlock(&test_fw_mutex);
+        return rc;
+}
+
+static const struct file_operations test_fw_fops = {
+        .owner          = THIS_MODULE,
+        .read           = test_fw_misc_read,
+};
+
+static struct miscdevice test_fw_misc_device = {
+        .minor          = MISC_DYNAMIC_MINOR,
+        .name           = "test_firmware",
+        .fops           = &test_fw_fops,
+};
+
+static ssize_t trigger_request_store(struct device *dev,
+                                     struct device_attribute *attr,
+                                     const char *buf, size_t count)
+{
+        int rc;
+        char *name;
+
+        name = kzalloc(count + 1, GFP_KERNEL);
+        if (!name)
+                return -ENOSPC;
+        memcpy(name, buf, count);
+
+        pr_info("loading '%s'\n", name);
+
+        mutex_lock(&test_fw_mutex);
+        release_firmware(test_firmware);
+        test_firmware = NULL;
+        rc = request_firmware(&test_firmware, name, dev);
+        if (rc)
+                pr_info("load of '%s' failed: %d\n", name, rc);
+        pr_info("loaded: %zu\n", test_firmware ? test_firmware->size : 0);
+        mutex_unlock(&test_fw_mutex);
+
+        kfree(name);
+
+        return count;
+}
+static DEVICE_ATTR_WO(trigger_request);
+
+static int __init test_firmware_init(void)
+{
+        int rc;
+
+        rc = misc_register(&test_fw_misc_device);
+        if (rc) {
+                pr_err("could not register misc device: %d\n", rc);
+                return rc;
+        }
+        rc = device_create_file(test_fw_misc_device.this_device,
+                                &dev_attr_trigger_request);
+        if (rc) {
+                pr_err("could not create sysfs interface: %d\n", rc);
+                goto dereg;
+        }
+
+        pr_warn("interface ready\n");
+
+        return 0;
+dereg:
+        misc_deregister(&test_fw_misc_device);
+        return rc;
+}
+
+module_init(test_firmware_init);
+
+static void __exit test_firmware_exit(void)
+{
+        release_firmware(test_firmware);
+        device_remove_file(test_fw_misc_device.this_device,
+                           &dev_attr_trigger_request);
+        misc_deregister(&test_fw_misc_device);
+        pr_warn("removed interface\n");
+}
+
+module_exit(test_firmware_exit);
+
+MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
+MODULE_LICENSE("GPL");