On Wed, Jan 23, 2019 at 09:44:12AM +0900, Tetsuo Handa wrote:
> Daniel Jordan wrote:
> > On Sat, Jan 19, 2019 at 11:41:22AM +0900, Tetsuo Handa wrote:
> > > On 2019/01/19 4:48, Daniel Jordan wrote:
> > > > On Sat, Jan 19, 2019 at 02:04:58AM +0900, Tetsuo Handa wrote:
> > > > __queue_work has a sanity check already for work, but using list_empty.
> > > > Seems
> > > > slightly better to be consistent?
> > > >
> > >
> > > list_empty() won't work, for "struct work_struct" is embedded into a
> > > struct
> > > which is allocated by kzalloc().
> >
> > Please check list_empty's definition again, it compares the address of the
> > node
> > to its next pointer, so it should work for a zeroed node. I'll reiterate
> > that
> > it seems slightly better to be consistent in "is work_struct initialized?"
> > checks, but it's not a big deal and I'm fine either way.
>
> You are talking about
>
> if (WARN_ON(!list_empty(&work->entry))) {
> spin_unlock(&pwq->pool->lock);
> return;
> }
>
> part in __queue_work(), aren't you? But since flush_work() is used for
> waiting for
> a work to complete, that work can be either queued state (list_empty() ==
> false) or
> not queued state (list_empty() == true). Thus, I don't think that
> flush_work() can
> use list_empty() for checking whether that work was initialized.
Oh, you're right, sorry for the noise!
> [PATCH v2] 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-ker...@i-love.sakura.ne.jp>
> ---
> kernel/workqueue.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 392be4b..a503ad9 100644
> --- 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);
Thanks for updating the changelog. FWIW, you can add
Reviewed-by: Daniel Jordan <daniel.m.jor...@oracle.com>
