workqueue: Try to catch flush_work() without INIT_WORK().

syzbot found a flush_work() caller who forgot to call INIT_WORK()
because that work_struct was allocated by kzalloc() [1]. But the message

  INFO: trying to register non-static key.
  the code is fine but needs lockdep annotation.
  turning off the locking correctness validator.

by lock_map_acquire() is failing to tell that INIT_WORK() is missing.

Since flush_work() without INIT_WORK() is a bug, and INIT_WORK() should
set ->func field to non-zero, let's warn if ->func field is zero.

[1] https://syzkaller.appspot.com/bug?id=a5954455fcfa51c29ca2ab55b203076337e1c770

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 392be4b252f69d02f5cd1770c17344b8067aec2f..a503ad9d0aec849e3bb1929b389eab3abb4236ad 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2908,6 +2908,9 @@ static bool __flush_work(struct work_struct *work, bool from_cancel)
        if (WARN_ON(!wq_online))
                return false;
 
+       if (WARN_ON(!work->func))
+               return false;
+
        if (!from_cancel) {
                lock_map_acquire(&work->lockdep_map);
                lock_map_release(&work->lockdep_map);