On 7/20/20 10:58 AM, Andy Lutomirski wrote: > >> 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. Sure, I'd consider that implementation detail for the actual patch(es) for this issue. -- Jens Axboe
