Re: io_uring vs in_compat_syscall()

[Jens Axboe]

On 7/20/20 12:10 AM, Christoph Hellwig wrote:
> Hi Jens,
> 
> I just found a (so far theoretical) issue with the io_uring submission
> offloading to workqueues or threads.  We have lots of places using
> in_compat_syscall() to check if a syscall needs compat treatmenet.
> While the biggest users is iocttl(), we also have a fair amount of
> places using in_compat_task() in read and write methods, and these
> will not do the wrong thing when used with io_uring under certain
> conditions.  I'm not sure how to best fix this, except for making sure
> in_compat_syscall() returns true one way or another for these cases.

We can probably propagate this information in the io_kiocb via a flag,
and have the io-wq worker set TS_COMPAT if that's the case.

-- 
Jens Axboe