On Sat, Sep 19, 2020 at 03:23:54PM -0700, Andy Lutomirski wrote: > > > On Sep 19, 2020, at 3:09 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > > > On Fri, Sep 18, 2020 at 05:16:15PM +0200, Christoph Hellwig wrote: > >>> On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote: > >>> Said that, why not provide a variant that would take an explicit > >>> "is it compat" argument and use it there? And have the normal > >>> one pass in_compat_syscall() to that... > >> > >> That would help to not introduce a regression with this series yes. > >> But it wouldn't fix existing bugs when io_uring is used to access > >> read or write methods that use in_compat_syscall(). One example that > >> I recently ran into is drivers/scsi/sg.c. > > > > So screw such read/write methods - don't use them with io_uring. > > That, BTW, is one of the reasons I'm sceptical about burying the > > decisions deep into the callchain - we don't _want_ different > > data layouts on read/write depending upon the 32bit vs. 64bit > > caller, let alone the pointer-chasing garbage that is /dev/sg. > > Well, we could remove in_compat_syscall(), etc and instead have an implicit parameter in DEFINE_SYSCALL. Then everything would have to be explicit. This would probably be a win, although it could be quite a bit of work. It would not be a win - most of the syscalls don't give a damn about 32bit vs. 64bit...
