diff options
| -rw-r--r-- | kernel/fork.c | 5 | ||||
| -rw-r--r-- | kernel/signal.c | 12 |
2 files changed, 15 insertions, 2 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index 9b7d746d6d62..9ca84189cfc2 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1022,11 +1022,14 @@ void __cleanup_sighand(struct sighand_struct *sighand) { if (atomic_dec_and_test(&sighand->count)) { signalfd_cleanup(sighand); + /* + * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it + * without an RCU grace period, see __lock_task_sighand(). + */ kmem_cache_free(sighand_cachep, sighand); } } - /* * Initialize POSIX timer handling for a thread group. */ diff --git a/kernel/signal.c b/kernel/signal.c index 54820984a872..19e35135fc60 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1275,7 +1275,17 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk, local_irq_restore(*flags); break; } - + /* + * This sighand can be already freed and even reused, but + * we rely on SLAB_DESTROY_BY_RCU and sighand_ctor() which + * initializes ->siglock: this slab can't go away, it has + * the same object type, ->siglock can't be reinitialized. + * + * We need to ensure that tsk->sighand is still the same + * after we take the lock, we can race with de_thread() or + * __exit_signal(). In the latter case the next iteration + * must see ->sighand == NULL. + */ spin_lock(&sighand->siglock); if (likely(sighand == tsk->sighand)) { rcu_read_unlock(); |