linux-kernel - [PATCH 4.19 055/100] workqueue: Try to catch flush_work() without INIT

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Message-Id: <20190430113611.541863454@linuxfoundation.org>
Date:   Tue, 30 Apr 2019 13:38:24 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Tejun Heo <tj@...nel.org>
Subject: [PATCH 4.19 055/100] workqueue: Try to catch flush_work() without INIT_WORK().

From: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>

commit 4d43d395fed124631ca02356c711facb90185175 upstream.

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@...ove.SAKURA.ne.jp>
Signed-off-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/workqueue.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2908,6 +2908,9 @@ static bool __flush_work(struct work_str
 	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);