Re: [syzbot] WARNING: locking bug in umh_complete

[Peter Zijlstra]

On Tue, Feb 14, 2023 at 10:31:58AM +0800, Schspa Shi wrote:
> Peter Zijlstra <peterz@xxxxxxxxxxxxx> writes:

> > If so, perhaps the simplest rule would to be ensure there is an
> > unconditional uninterruptible wait-for-completion() before going out of
> > scope.
> >
> > This latter can be spelled like wait_for_completion() or
> > wait_for_completion_state(TASK_UNINTERRUPTIBLE). More specifically,
> > TASK_INTERRUPTIBLE and TASK_WAKEKILL must not be set in the state mask
> > for the wait to be uninterruptible.
> >
> > If it cannot be proven, raise a warning and audit or somesuch.
> 
> This is a good suggestion. I have written a SmPL patch to complete this
> check, and now I need to rule out the situation that the driver has
> added an additional lock to protect it.
> 
> And I have found a lot of bad usage, should we consider adding a new
> helper API to simplify the fix this?

Please first share some of the locations where this would be applied.