[PATCH 4.19 44/45] cgroup: Fix css_task_iter_advance_css_set() cset skip condition

[Greg Kroah-Hartman]

From: Tejun Heo <tj@xxxxxxxxxx>

commit c596687a008b579c503afb7a64fcacc7270fae9e upstream.

While adding handling for dying task group leaders c03cd7738a83
("cgroup: Include dying leaders with live threads in PROCS
iterations") added an inverted cset skip condition to
css_task_iter_advance_css_set().  It should skip cset if it's
completely empty but was incorrectly testing for the inverse condition
for the dying_tasks list.  Fix it.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Fixes: c03cd7738a83 ("cgroup: Include dying leaders with live threads in PROCS iterations")
Reported-by: syzbot+d4bba5ccd4f9a2a68681@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/cgroup/cgroup.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4154,7 +4154,7 @@ static void css_task_iter_advance_css_se
 			it->task_pos = NULL;
 			return;
 		}
-	} while (!css_set_populated(cset) && !list_empty(&cset->dying_tasks));
+	} while (!css_set_populated(cset) && list_empty(&cset->dying_tasks));
 
 	if (!list_empty(&cset->tasks))
 		it->task_pos = cset->tasks.next;