From 355cae1bbdbf958d82ad6788f037ade224bd1270 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marco=20Trevisan=20=28Trevi=C3=B1o=29?= <mail@3v1n0.net>
Date: Sat, 8 Feb 2020 13:38:18 +0100
Subject: [PATCH] fp-device: Return error if trying to list a storage-less
 device

Devices with no storage don't allow listing prints, and if we try to do
that, we'd end up in trying to call a NULL function pointer, causing a crash

So always check if the device has storage before calling the list vfunc, and
if we fail, return an error.

Include an unit-test to verify this situation
---
 libfprint/fp-device.c   |  8 ++++++++
 tests/test-fpi-device.c | 19 +++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/libfprint/fp-device.c b/libfprint/fp-device.c
index 40b3efa..fe36eae 100644
--- a/libfprint/fp-device.c
+++ b/libfprint/fp-device.c
@@ -1213,6 +1213,14 @@ fp_device_list_prints (FpDevice           *device,
       return;
     }
 
+  if (!fp_device_has_storage (device))
+    {
+      g_task_return_error (task,
+                           fpi_device_error_new_msg (FP_DEVICE_ERROR_NOT_SUPPORTED,
+                                                     "Device has no storage"));
+      return;
+    }
+
   priv->current_action = FPI_DEVICE_ACTION_LIST;
   priv->current_task = g_steal_pointer (&task);
   maybe_cancel_on_cancelled (device, cancellable);
diff --git a/tests/test-fpi-device.c b/tests/test-fpi-device.c
index bfe383b..0e66c2e 100644
--- a/tests/test-fpi-device.c
+++ b/tests/test-fpi-device.c
@@ -1527,6 +1527,24 @@ test_driver_list_error (void)
   g_assert_null (prints);
 }
 
+static void
+test_driver_list_no_storage (void)
+{
+  g_autoptr(FpAutoResetClass) dev_class = auto_reset_device_class ();
+  g_autoptr(FpAutoCloseDevice) device = NULL;
+  g_autoptr(GPtrArray) prints = NULL;
+  g_autoptr(GError) error = NULL;
+
+  dev_class->list = NULL;
+
+  device = auto_close_fake_device_new ();
+  g_assert_false (fp_device_has_storage (device));
+
+  prints = fp_device_list_prints_sync (device, NULL, &error);
+  g_assert_null (prints);
+  g_assert_error (error, FP_DEVICE_ERROR, FP_DEVICE_ERROR_NOT_SUPPORTED);
+}
+
 static void
 test_driver_delete (void)
 {
@@ -2210,6 +2228,7 @@ main (int argc, char *argv[])
   g_test_add_func ("/driver/capture/error", test_driver_capture_error);
   g_test_add_func ("/driver/list", test_driver_list);
   g_test_add_func ("/driver/list/error", test_driver_list_error);
+  g_test_add_func ("/driver/list/no_storage", test_driver_list_no_storage);
   g_test_add_func ("/driver/delete", test_driver_delete);
   g_test_add_func ("/driver/delete/error", test_driver_delete_error);
   g_test_add_func ("/driver/cancel", test_driver_cancel);