Merge tag 'seccomp-v6.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull seccomp updates from Kees Cook:

 - interrupt SECCOMP_IOCTL_NOTIF_RECV when all users exit (Andrei Vagin)

 - Update selftests to check for expected NOTIF_RECV exits (Andrei
   Vagin)

* tag 'seccomp-v6.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  selftests/seccomp: check that a zombie leader doesn't affect others
  selftests/seccomp: add test for NOTIF_RECV and unused filters
  seccomp: release task filters when the task exits
  seccomp: interrupt SECCOMP_IOCTL_NOTIF_RECV when all users have exited

2 files changed, 26 insertions, 7 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 81fcee45d630..be81342caf1b 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -277,7 +277,6 @@ repeat:
 	}
 
 	write_unlock_irq(&tasklist_lock);
-	seccomp_filter_release(p);
 	proc_flush_pid(thread_pid);
 	put_pid(thread_pid);
 	release_thread(p);
@@ -834,6 +833,8 @@ void __noreturn do_exit(long code)
 	io_uring_files_cancel();
 	exit_signals(tsk);  /* sets PF_EXITING */
 
+	seccomp_filter_release(tsk);
+
 	acct_update_integrals(tsk);
 	group_dead = atomic_dec_and_test(&tsk->signal->live);
 	if (group_dead) {
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index e30b60b57614..dc51e521bc1d 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -502,6 +502,9 @@ static inline pid_t seccomp_can_sync_threads(void)
 		/* Skip current, since it is initiating the sync. */
 		if (thread == caller)
 			continue;
+		/* Skip exited threads. */
+		if (thread->flags & PF_EXITING)
+			continue;
 
 		if (thread->seccomp.mode == SECCOMP_MODE_DISABLED ||
 		    (thread->seccomp.mode == SECCOMP_MODE_FILTER &&
@@ -563,18 +566,21 @@ static void __seccomp_filter_release(struct seccomp_filter *orig)
  * @tsk: task the filter should be released from.
  *
  * This function should only be called when the task is exiting as
- * it detaches it from its filter tree. As such, READ_ONCE() and
- * barriers are not needed here, as would normally be needed.
+ * it detaches it from its filter tree. PF_EXITING has to be set
+ * for the task.
  */
 void seccomp_filter_release(struct task_struct *tsk)
 {
-	struct seccomp_filter *orig = tsk->seccomp.filter;
+	struct seccomp_filter *orig;
 
-	/* We are effectively holding the siglock by not having any sighand. */
-	WARN_ON(tsk->sighand != NULL);
+	if (WARN_ON((tsk->flags & PF_EXITING) == 0))
+		return;
 
+	spin_lock_irq(&tsk->sighand->siglock);
+	orig = tsk->seccomp.filter;
 	/* Detach task from its filter tree. */
 	tsk->seccomp.filter = NULL;
+	spin_unlock_irq(&tsk->sighand->siglock);
 	__seccomp_filter_release(orig);
 }
 
@@ -602,6 +608,13 @@ static inline void seccomp_sync_threads(unsigned long flags)
 		if (thread == caller)
 			continue;
 
+		/*
+		 * Skip exited threads. seccomp_filter_release could have
+		 * been already called for this task.
+		 */
+		if (thread->flags & PF_EXITING)
+			continue;
+
 		/* Get a task reference for the new leaf node. */
 		get_seccomp_filter(caller);
 
@@ -1466,7 +1479,7 @@ static int recv_wake_function(wait_queue_entry_t *wait, unsigned int mode, int s
 				  void *key)
 {
 	/* Avoid a wakeup if event not interesting for us. */
-	if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR)))
+	if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR | EPOLLHUP)))
 		return 0;
 	return autoremove_wake_function(wait, mode, sync, key);
 }
@@ -1476,6 +1489,9 @@ static int recv_wait_event(struct seccomp_filter *filter)
 	DEFINE_WAIT_FUNC(wait, recv_wake_function);
 	int ret;
 
+	if (refcount_read(&filter->users) == 0)
+		return 0;
+
 	if (atomic_dec_if_positive(&filter->notif->requests) >= 0)
 		return 0;
 
@@ -1484,6 +1500,8 @@ static int recv_wait_event(struct seccomp_filter *filter)
 
 		if (atomic_dec_if_positive(&filter->notif->requests) >= 0)
 			break;
+		if (refcount_read(&filter->users) == 0)
+			break;
 
 		if (ret)
 			return ret;