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.
[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);
