> On Jul 20, 2020, at 9:37 AM, Jens Axboe <axboe@xxxxxxxxx> wrote: > > 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. > Is TS_COMPAT actually a cross-arch concept for which this is safe? Having a real arch helper for “set the current syscall arch for the current kernel thread” seems more sensible to me.
