Hi Suren, I love your patch! Perhaps something to improve: [auto build test WARNING on linux/master] [also build test WARNING on tj-cgroup/for-next linus/master v5.16 next-20220112] [cannot apply to tip/sched/core] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch] url: https://github.com/0day-ci/linux/commits/Suren-Baghdasaryan/psi-Fix-uaf-i... base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git fe8152b38d3a994c4c6fdbc0cd6551d569a5715a config: s390-randconfig-r011-20220112 (https://download.01.org/0day-ci/archive/20220113/202201130006.50syZ3rt-lk...) compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 244dd2913a43a200f5a6544d424cdc37b771028b) 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 # install s390 cross compiling tool for clang build # apt-get install binutils-s390x-linux-gnu # https://github.com/0day-ci/linux/commit/81c75158e8d3b743a8bdc51cec94b938c... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Suren-Baghdasaryan/psi-Fix-uaf-issue-when-psi-trigger-is-destroyed-while-being-polled/20220112-072341 git checkout 81c75158e8d3b743a8bdc51cec94b938c027286d # save the config file to linux build tree mkdir build_dir COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=s390 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 >>): In file included from kernel/sched/psi.c:146: In file included from kernel/sched/sched.h:17: In file included from include/linux/sched/isolation.h:6: In file included from include/linux/tick.h:8: In file included from include/linux/clockchips.h:14: In file included from include/linux/clocksource.h:22: In file included from arch/s390/include/asm/io.h:75: include/asm-generic/io.h:464:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] val = __raw_readb(PCI_IOBASE + addr); ~~~~~~~~~~ ^ include/asm-generic/io.h:477:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr)); ~~~~~~~~~~ ^ include/uapi/linux/byteorder/big_endian.h:37:59: note: expanded from macro '__le16_to_cpu' #define __le16_to_cpu(x) __swab16((__force __u16)(__le16)(x)) ^ include/uapi/linux/swab.h:102:54: note: expanded from macro '__swab16' #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x)) ^ In file included from kernel/sched/psi.c:146: In file included from kernel/sched/sched.h:17: In file included from include/linux/sched/isolation.h:6: In file included from include/linux/tick.h:8: In file included from include/linux/clockchips.h:14: In file included from include/linux/clocksource.h:22: In file included from arch/s390/include/asm/io.h:75: include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr)); ~~~~~~~~~~ ^ include/uapi/linux/byteorder/big_endian.h:35:59: note: expanded from macro '__le32_to_cpu' #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x)) ^ include/uapi/linux/swab.h:115:54: note: expanded from macro '__swab32' #define __swab32(x) (__u32)__builtin_bswap32((__u32)(x)) ^ In file included from kernel/sched/psi.c:146: In file included from kernel/sched/sched.h:17: In file included from include/linux/sched/isolation.h:6: In file included from include/linux/tick.h:8: In file included from include/linux/clockchips.h:14: In file included from include/linux/clocksource.h:22: In file included from arch/s390/include/asm/io.h:75: include/asm-generic/io.h:501:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] __raw_writeb(value, PCI_IOBASE + addr); ~~~~~~~~~~ ^ include/asm-generic/io.h:511:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr); ~~~~~~~~~~ ^ include/asm-generic/io.h:521:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr); ~~~~~~~~~~ ^ include/asm-generic/io.h:609:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] readsb(PCI_IOBASE + addr, buffer, count); ~~~~~~~~~~ ^ include/asm-generic/io.h:617:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] readsw(PCI_IOBASE + addr, buffer, count); ~~~~~~~~~~ ^ include/asm-generic/io.h:625:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] readsl(PCI_IOBASE + addr, buffer, count); ~~~~~~~~~~ ^ include/asm-generic/io.h:634:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] writesb(PCI_IOBASE + addr, buffer, count); ~~~~~~~~~~ ^ include/asm-generic/io.h:643:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] writesw(PCI_IOBASE + addr, buffer, count); ~~~~~~~~~~ ^ include/asm-generic/io.h:652:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] writesl(PCI_IOBASE + addr, buffer, count); ~~~~~~~~~~ ^ kernel/sched/psi.c:1112:21: warning: no previous prototype for function 'psi_trigger_create' [-Wmissing-prototypes] struct psi_trigger *psi_trigger_create(struct psi_group *group, ^ kernel/sched/psi.c:1112:1: note: declare 'static' if the function is not intended to be used outside of this translation unit struct psi_trigger *psi_trigger_create(struct psi_group *group, ^ static void psi_trigger_destroy(struct psi_trigger *t) ^ kernel/sched/psi.c:1182:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void psi_trigger_destroy(struct psi_trigger *t) ^ static kernel/sched/psi.c:1249:10: warning: no previous prototype for function 'psi_trigger_poll' [-Wmissing-prototypes] __poll_t psi_trigger_poll(void **trigger_ptr, ^ kernel/sched/psi.c:1249:1: note: declare 'static' if the function is not intended to be used outside of this translation unit __poll_t psi_trigger_poll(void **trigger_ptr, ^ static 15 warnings generated. vim +/psi_trigger_destroy +1182 kernel/sched/psi.c 1181 1183 { 1184 struct psi_group *group; 1185 struct task_struct *task_to_destroy = NULL; 1186 1187 /* 1188 * We do not check psi_disabled since it might have been disabled after 1189 * the trigger got created. 1190 */ 1191 if (!t) 1192 return; 1193 1194 group = t->group; 1195 /* 1196 * Wakeup waiters to stop polling. Can happen if cgroup is deleted 1197 * from under a polling process. 1198 */ 1199 wake_up_interruptible(&t->event_wait); 1200 1201 mutex_lock(&group->trigger_lock); 1202 1203 if (!list_empty(&t->node)) { 1204 struct psi_trigger *tmp; 1205 u64 period = ULLONG_MAX; 1206 1207 list_del(&t->node); 1208 group->nr_triggers[t->state]--; 1209 if (!group->nr_triggers[t->state]) 1210 group->poll_states &= ~(1 << t->state); 1211 /* reset min update period for the remaining triggers */ 1212 list_for_each_entry(tmp, &group->triggers, node) 1213 period = min(period, div_u64(tmp->win.size, 1214 UPDATES_PER_WINDOW)); 1215 group->poll_min_period = period; 1216 /* Destroy poll_task when the last trigger is destroyed */ 1217 if (group->poll_states == 0) { 1218 group->polling_until = 0; 1219 task_to_destroy = rcu_dereference_protected( 1220 group->poll_task, 1221 lockdep_is_held(&group->trigger_lock)); 1222 rcu_assign_pointer(group->poll_task, NULL); 1223 del_timer(&group->poll_timer); 1224 } 1225 } 1226 1227 mutex_unlock(&group->trigger_lock); 1228 1229 /* 1230 * Wait for psi_schedule_poll_work RCU to complete its read-side 1231 * critical section before destroying the trigger and optionally the 1232 * poll_task. 1233 */ 1234 synchronize_rcu(); 1235 /* 1236 * Stop kthread 'psimon' after releasing trigger_lock to prevent a 1237 * deadlock while waiting for psi_poll_work to acquire trigger_lock 1238 */ 1239 if (task_to_destroy) { 1240 /* 1241 * After the RCU grace period has expired, the worker 1242 * can no longer be found through group->poll_task. 1243 */ 1244 kthread_stop(task_to_destroy); 1245 } 1246 kfree(t); 1247 } 1248 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org