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. Run task_works in the freezer path. Keep the patch small and simple so it can be easily back ported, but we might need to do some cleaning after and look if there are other places with similar problems. Cc: stable@xxxxxxxxxxxxxxx Link: https://github.com/systemd/systemd/issues/33626 Fixes: 12db8b690010c ("entry: Add support for TIF_NOTIFY_SIGNAL") Reported-by: Julian Orth <ju.orth@xxxxxxxxx> Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx> Acked-by: Tejun Heo <tj@xxxxxxxxxx> Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx> --- kernel/signal.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/signal.c b/kernel/signal.c index 1f9dd41c04be..60c737e423a1 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2600,6 +2600,14 @@ static void do_freezer_trap(void) spin_unlock_irq(¤t->sighand->siglock); cgroup_enter_frozen(); schedule(); + + /* + * We could've been woken by task_work, run it to clear + * TIF_NOTIFY_SIGNAL. The caller will retry if necessary. + */ + clear_notify_signal(); + if (unlikely(task_work_pending(current))) + task_work_run(); } static int ptrace_signal(int signr, kernel_siginfo_t *info, enum pid_type type) -- 2.44.0
