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-lk...) 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... 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(a)intel.com&gt; 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, | ^~~~~~~~~~~~~~~~~~ 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, | ^~~~~~~~~~~~~~~~ vim +/psi_trigger_destroy +1193 kernel/sched/psi.c 1192 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@lists.01.org