diff options
| -rw-r--r-- | tools/perf/util/machine.c | 25 | ||||
| -rw-r--r-- | tools/perf/util/thread.c | 23 |
2 files changed, 43 insertions, 5 deletions
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index dc7aafe45a2b..e00dc413652d 100644 --- a/tools/perf/util/machine.c +++ b/tools/perf/util/machine.c @@ -209,6 +209,18 @@ void machine__exit(struct machine *machine) for (i = 0; i < THREADS__TABLE_SIZE; i++) { struct threads *threads = &machine->threads[i]; + struct thread *thread, *n; + /* + * Forget about the dead, at this point whatever threads were + * left in the dead lists better have a reference count taken + * by who is using them, and then, when they drop those references + * and it finally hits zero, thread__put() will check and see that + * its not in the dead threads list and will not try to remove it + * from there, just calling thread__delete() straight away. + */ + list_for_each_entry_safe(thread, n, &threads->dead, node) + list_del_init(&thread->node); + exit_rwsem(&threads->lock); } } @@ -1758,9 +1770,11 @@ static void __machine__remove_thread(struct machine *machine, struct thread *th, if (threads->last_match == th) threads__set_last_match(threads, NULL); - BUG_ON(refcount_read(&th->refcnt) == 0); if (lock) down_write(&threads->lock); + + BUG_ON(refcount_read(&th->refcnt) == 0); + rb_erase_cached(&th->rb_node, &threads->entries); RB_CLEAR_NODE(&th->rb_node); --threads->nr; @@ -1770,9 +1784,16 @@ static void __machine__remove_thread(struct machine *machine, struct thread *th, * will be called and we will remove it from the dead_threads list. */ list_add_tail(&th->node, &threads->dead); + + /* + * We need to do the put here because if this is the last refcount, + * then we will be touching the threads->dead head when removing the + * thread. + */ + thread__put(th); + if (lock) up_write(&threads->lock); - thread__put(th); } void machine__remove_thread(struct machine *machine, struct thread *th) diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c index b413ba5b9835..7bfb740d2ede 100644 --- a/tools/perf/util/thread.c +++ b/tools/perf/util/thread.c @@ -125,10 +125,27 @@ void thread__put(struct thread *thread) { if (thread && refcount_dec_and_test(&thread->refcnt)) { /* - * Remove it from the dead_threads list, as last reference - * is gone. + * Remove it from the dead threads list, as last reference is + * gone, if it is in a dead threads list. + * + * We may not be there anymore if say, the machine where it was + * stored was already deleted, so we already removed it from + * the dead threads and some other piece of code still keeps a + * reference. + * + * This is what 'perf sched' does and finally drops it in + * perf_sched__lat(), where it calls perf_sched__read_events(), + * that processes the events by creating a session and deleting + * it, which ends up destroying the list heads for the dead + * threads, but before it does that it removes all threads from + * it using list_del_init(). + * + * So we need to check here if it is in a dead threads list and + * if so, remove it before finally deleting the thread, to avoid + * an use after free situation. */ - list_del_init(&thread->node); + if (!list_empty(&thread->node)) + list_del_init(&thread->node); thread__delete(thread); } } |