Re: [syzbot] WARNING: locking bug in umh_complete

[Schspa Shi]

Peter Zijlstra <peterz@xxxxxxxxxxxxx> writes:

> 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.

Hi Peter:

I started a new thread to discuss the SmPL patch.

Link: https://lore.kernel.org/all/20230227075346.69658-1-schspa@xxxxxxxxx/

-- 
BRs
Schspa Shi