[PATCH 2/2] kernel: rerun task_work while freezing in get_signal()

[Pavel Begunkov]

io_uring can asynchronously add a task_work while the task is getting
freezed. TIF_NOTIFY_SIGNAL will prevent the task from sleeping in
do_freezer_trap(), and since the get_signal()'s relock loop doesn't
retry task_work, the task will spin there not being able to sleep
until the freezing is cancelled / the task is killed / etc.

Cc: stable@xxxxxxxxxxxxxxx
Link: https://github.com/systemd/systemd/issues/33626
Fixes: 3146cba99aa28 ("io-wq: make worker creation resilient against signals")
Reported-by: Julian Orth <ju.orth@xxxxxxxxx>
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
 kernel/signal.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/signal.c b/kernel/signal.c
index 1f9dd41c04be..790d60fcfff0 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2694,6 +2694,10 @@ bool get_signal(struct ksignal *ksig)
 	try_to_freeze();
 
 relock:
+	clear_notify_signal();
+	if (unlikely(task_work_pending(current)))
+		task_work_run();
+
 	spin_lock_irq(&sighand->siglock);
 
 	/*
-- 
2.44.0