Re: kernel/sched/psi.c:1193:6: warning: no previous prototype for 'psi_trigger_destroy'

[Suren Baghdasaryan]

On Mon, Jan 24, 2022 at 4:27 PM kernel test robot <lkp@xxxxxxxxx> wrote:
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   dd81e1c7d5fb126e5fbc5c9e334d7b3ec29a16a0
> commit: a06247c6804f1a7c86a2e5398a4c1f1db1471848 psi: Fix uaf issue when psi trigger is destroyed while being polled
> date:   7 days ago
> config: sh-randconfig-r012-20220124 (https://download.01.org/0day-ci/archive/20220125/202201250818.178Aw4sD-lkp@xxxxxxxxx/config)
> compiler: sh4-linux-gcc (GCC) 11.2.0
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a06247c6804f1a7c86a2e5398a4c1f1db1471848
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout a06247c6804f1a7c86a2e5398a4c1f1db1471848
>         # save the config file to linux build tree
>         mkdir build_dir
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=sh SHELL=/bin/bash kernel/sched/
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
>
> All warnings (new ones prefixed by >>):
>
>    kernel/sched/psi.c:1123:21: warning: no previous prototype for 'psi_trigger_create' [-Wmissing-prototypes]
>     1123 | struct psi_trigger *psi_trigger_create(struct psi_group *group,
>          |                     ^~~~~~~~~~~~~~~~~~
> >> kernel/sched/psi.c:1193:6: warning: no previous prototype for 'psi_trigger_destroy' [-Wmissing-prototypes]
>     1193 | void psi_trigger_destroy(struct psi_trigger *t)
>          |      ^~~~~~~~~~~~~~~~~~~
>    kernel/sched/psi.c:1260:10: warning: no previous prototype for 'psi_trigger_poll' [-Wmissing-prototypes]
>     1260 | __poll_t psi_trigger_poll(void **trigger_ptr,
>          |          ^~~~~~~~~~~~~~~~
>

https://lore.kernel.org/all/YemFa5ouZXEnR%2FD+@xxxxxxxxxxx fixes these warnings.

>
> vim +/psi_trigger_destroy +1193 kernel/sched/psi.c
>
>   1192
> > 1193  void psi_trigger_destroy(struct psi_trigger *t)
>   1194  {
>   1195          struct psi_group *group;
>   1196          struct task_struct *task_to_destroy = NULL;
>   1197
>   1198          /*
>   1199           * We do not check psi_disabled since it might have been disabled after
>   1200           * the trigger got created.
>   1201           */
>   1202          if (!t)
>   1203                  return;
>   1204
>   1205          group = t->group;
>   1206          /*
>   1207           * Wakeup waiters to stop polling. Can happen if cgroup is deleted
>   1208           * from under a polling process.
>   1209           */
>   1210          wake_up_interruptible(&t->event_wait);
>   1211
>   1212          mutex_lock(&group->trigger_lock);
>   1213
>   1214          if (!list_empty(&t->node)) {
>   1215                  struct psi_trigger *tmp;
>   1216                  u64 period = ULLONG_MAX;
>   1217
>   1218                  list_del(&t->node);
>   1219                  group->nr_triggers[t->state]--;
>   1220                  if (!group->nr_triggers[t->state])
>   1221                          group->poll_states &= ~(1 << t->state);
>   1222                  /* reset min update period for the remaining triggers */
>   1223                  list_for_each_entry(tmp, &group->triggers, node)
>   1224                          period = min(period, div_u64(tmp->win.size,
>   1225                                          UPDATES_PER_WINDOW));
>   1226                  group->poll_min_period = period;
>   1227                  /* Destroy poll_task when the last trigger is destroyed */
>   1228                  if (group->poll_states == 0) {
>   1229                          group->polling_until = 0;
>   1230                          task_to_destroy = rcu_dereference_protected(
>   1231                                          group->poll_task,
>   1232                                          lockdep_is_held(&group->trigger_lock));
>   1233                          rcu_assign_pointer(group->poll_task, NULL);
>   1234                          del_timer(&group->poll_timer);
>   1235                  }
>   1236          }
>   1237
>   1238          mutex_unlock(&group->trigger_lock);
>   1239
>   1240          /*
>   1241           * Wait for psi_schedule_poll_work RCU to complete its read-side
>   1242           * critical section before destroying the trigger and optionally the
>   1243           * poll_task.
>   1244           */
>   1245          synchronize_rcu();
>   1246          /*
>   1247           * Stop kthread 'psimon' after releasing trigger_lock to prevent a
>   1248           * deadlock while waiting for psi_poll_work to acquire trigger_lock
>   1249           */
>   1250          if (task_to_destroy) {
>   1251                  /*
>   1252                   * After the RCU grace period has expired, the worker
>   1253                   * can no longer be found through group->poll_task.
>   1254                   */
>   1255                  kthread_stop(task_to_destroy);
>   1256          }
>   1257          kfree(t);
>   1258  }
>   1259
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx