testing/drivertest: add sensor watchdog regression test.

Issue apache/nuttx#20145 reported a sensor fetch-watchdog lifetime
regression: sensor_poll() arms a per-subscriber watchdog for
fetch-only sensors with a finite interval, but sensor_close()
freed the subscriber without cancelling it, letting
sensor_fetch_expired() run after free.

Fixed by apache/nuttx#20146, which cancels the watchdog on close.
Add regression coverage in drivertest as suggested by the maintainer:
open a sensor device, set a finite fetch interval, enter the poll
path so the watchdog can be armed, then close while the watchdog
state is relevant. Sleep past the interval so any stray timer would
fire, and reopen to prove teardown was clean. The test skips
gracefully when no sensor device is present, so it is safe on sim
without hardware.

The test does not deterministically reproduce the UAF; it verifies
the observable invariant that repeated poll/close/reopen cycles
complete cleanly and the device remains usable. Under KASAN or
stress, a missing wd_cancel in close would be caught here.

Impact:
* Is new feature added? YES (new regression test coverage in
  testing/drivers/drivertest, no existing functionality changed).
* Impact on user, build, hardware, documentation, security,
  compatibility? NO, test-only change.

Testing:
* Full build and runtime logs are provided in the PR description.

Assisted-by: Muse Spark:muse-spark-1.3
Assisted-by: Claude:claude-opus
Signed-off-by: Arnav Sharma <2006arnavsharma@gmail.com>

testing/drivers/drivertest/CMakeLists.txt

@@ -87,6 +87,22 @@ if(CONFIG_TESTING_DRIVER_TEST)
       drivertest_timer.c)
   endif()
 
+  if(CONFIG_SENSORS)
+    nuttx_add_application(
+      NAME
+      cmocka_driver_sensor
+      PRIORITY
+      ${CONFIG_TESTING_DRIVER_TEST_PRIORITY}
+      STACKSIZE
+      ${CONFIG_TESTING_DRIVER_TEST_STACKSIZE}
+      MODULE
+      ${CONFIG_TESTING_DRIVER_TEST}
+      DEPENDS
+      cmocka
+      SRCS
+      drivertest_sensor.c)
+  endif()
+
   if(CONFIG_TESTING_ONESHOT_TEST)
     nuttx_add_application(
       NAME

testing/drivers/drivertest/Makefile

@@ -49,6 +49,11 @@ MAINSRC  += drivertest_timer.c
 PROGNAME += cmocka_driver_timer
 endif
 
+ifneq ($(CONFIG_SENSORS),)
+MAINSRC  += drivertest_sensor.c
+PROGNAME += cmocka_driver_sensor
+endif
+
 ifneq ($(CONFIG_TESTING_ONESHOT_TEST),)
 MAINSRC  += drivertest_oneshot.c
 PROGNAME += cmocka_driver_oneshot

testing/drivers/drivertest/drivertest_sensor.c

@@ -0,0 +1,236 @@
+/****************************************************************************
+ * apps/testing/drivers/drivertest/drivertest_sensor.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/ioctl.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <stdarg.h>
+#include <stddef.h>
+#include <setjmp.h>
+#include <stdint.h>
+#include <cmocka.h>
+
+#include <nuttx/sensors/sensor.h>
+#include <nuttx/sensors/ioctl.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#define SENSOR_DEVPATH      "/dev/uorb/sensor_baro0"
+#define SENSOR_INTERVAL     100000
+#define SENSOR_COUNT        5
+#define SENSOR_READ_BUFSIZE 128
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+struct sensortest_state_s
+{
+  char devpath[PATH_MAX];
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: show_usage
+ ****************************************************************************/
+
+static void show_usage(FAR const char *progname,
+                       FAR struct sensortest_state_s *sensor_state,
+                       int exitcode)
+{
+  printf("Usage: %s [-d <devpath>]\n", progname);
+  printf("  [-d devpath] selects the sensor device.\n"
+         "  Default: %s Current: %s\n",
+         SENSOR_DEVPATH, sensor_state->devpath);
+  printf("  [-h] = Shows this message and exits\n");
+
+  exit(exitcode);
+}
+
+/****************************************************************************
+ * Name: parse_commandline
+ ****************************************************************************/
+
+static void parse_commandline(FAR struct sensortest_state_s *sensor_state,
+                              int argc, FAR char **argv)
+{
+  int ch;
+
+  while ((ch = getopt(argc, argv, "d:h")) != ERROR)
+    {
+      switch (ch)
+        {
+          case 'd':
+            strlcpy(sensor_state->devpath, optarg,
+                    sizeof(sensor_state->devpath));
+            break;
+
+          case '?':
+            printf("Unsupported option: %s\n", optarg);
+            show_usage(argv[0], sensor_state, EXIT_FAILURE);
+            break;
+
+          default:
+            show_usage(argv[0], sensor_state, EXIT_FAILURE);
+            break;
+        }
+    }
+}
+
+/****************************************************************************
+ * Name: drivertest_sensor_fetch_wdog
+ *
+ * Description:
+ *   Regression test for apache/nuttx#20145, fixed by apache/nuttx#20146.
+ *   sensor_poll() arms a per-subscriber watchdog for fetch-only sensors
+ *   with a finite interval, but sensor_close() used to free the
+ *   subscriber without cancelling it, letting sensor_fetch_expired()
+ *   run after free. The test sets a finite interval, polls so the
+ *   watchdog can arm, closes, waits past the interval so any stray
+ *   timer would fire, and reopens to prove teardown was clean. It does
+ *   not deterministically reproduce the UAF; under KASAN or stress a
+ *   missing wd_cancel in close would be caught here.
+ *
+ ****************************************************************************/
+
+static void drivertest_sensor_fetch_wdog(FAR void **state)
+{
+  FAR struct sensortest_state_s *sensor_state;
+  char buffer[SENSOR_READ_BUFSIZE];
+  struct pollfd fds;
+  unsigned int i;
+  int fd;
+  int ret;
+
+  sensor_state = (FAR struct sensortest_state_s *)*state;
+
+  fd = open(sensor_state->devpath, O_RDONLY);
+  if (fd < 0)
+    {
+      if (errno == ENOENT || errno == ENODEV || errno == ENXIO)
+        {
+          printf("Sensor device %s not present, skipping test\n",
+                 sensor_state->devpath);
+          return;
+        }
+
+      assert_true(fd >= 0);
+    }
+
+  ret = ioctl(fd, SNIOC_SET_INTERVAL, SENSOR_INTERVAL);
+  if (ret < 0 && (errno == ENOTSUP || errno == ENOTTY))
+    {
+      printf("Sensor device %s does not support intervals, "
+             "skipping test\n", sensor_state->devpath);
+      close(fd);
+      return;
+    }
+
+  assert_return_code(ret, OK);
+
+  for (i = 0; i < SENSOR_COUNT; i++)
+    {
+      /* First poll reports POLLIN once per interval for a fetch-only
+       * sensor and records the timestamp the pacing is based on.
+       */
+
+      fds.fd = fd;
+      fds.events = POLLIN;
+      fds.revents = 0;
+      ret = poll(&fds, 1, 0);
+      assert_true(ret >= 0);
+
+      if (ret > 0 && (fds.revents & POLLIN))
+        {
+          ret = read(fd, buffer, sizeof(buffer));
+          assert_true(ret >= 0);
+        }
+
+      /* Second poll arms user->wdog (elapsed < interval). Closing
+       * here exercises the lifetime fixed by #20146.
+       */
+
+      fds.fd = fd;
+      fds.events = POLLIN;
+      fds.revents = 0;
+      ret = poll(&fds, 1, 0);
+      assert_true(ret >= 0);
+
+      ret = close(fd);
+      assert_return_code(ret, OK);
+
+      /* Let any stray timer fire before reopening. */
+
+      usleep(SENSOR_INTERVAL * 2);
+
+      fd = open(sensor_state->devpath, O_RDONLY);
+      assert_true(fd >= 0);
+
+      ret = ioctl(fd, SNIOC_SET_INTERVAL, SENSOR_INTERVAL);
+      assert_return_code(ret, OK);
+    }
+
+  ret = close(fd);
+  assert_return_code(ret, OK);
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: main
+ ****************************************************************************/
+
+int main(int argc, FAR char *argv[])
+{
+  struct sensortest_state_s sensor_state =
+  {
+    .devpath = SENSOR_DEVPATH,
+  };
+
+  parse_commandline(&sensor_state, argc, argv);
+
+  const struct CMUnitTest tests[] =
+  {
+    cmocka_unit_test_prestate(drivertest_sensor_fetch_wdog, &sensor_state),
+  };
+
+  return cmocka_run_group_tests(tests, NULL, NULL);
+}