On Thu, Jul 30, 2020 at 11:18:04AM +0200, Arnd Bergmann wrote: > On Thu, Jul 30, 2020 at 10:38 AM Andy Shevchenko > <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: > > On Thu, Jul 30, 2020 at 10:15:24AM +0200, Arnd Bergmann wrote: > > > On Thu, Jul 30, 2020 at 10:07 AM Bartosz Golaszewski <brgl@xxxxxxxx> wrote: ... > > > I would argue that it needs to be fixed anyway, unless you also want > > > to remove the v1 interface for native mode. If this works on 32-bit > > > kernels, on 64-bit kernels with 64-bit user space and on compat > > > 32-bit user space on 64-bit non-x86 architectures, I see no reason > > > to leave it broken specifically on x86 compat user space. There are > > > still reasons to use 32-bit x86 user space for low-memory machines > > > even though native i386 kernels are getting increasingly silly. > > > > It was possible to "fix" (mitigate to some extent) before libgpiod got support > > for several events in a request. Now it seems to be impossible to fix. AFAIU we > > must discard any request to more than one event in it. > > Any reason why the workaround I suggested above would not work? That is the question to somebody who has better understanding. If it works, I vote up to get it fixed with little effort. I would be glad to test patches! > The in_ia32_syscall() check should be completely reliable in telling whether > we are called from read() by an ia32 task or not, and we use the same > logic for input_event, which has a similar problem (on all compat architectures, > not just x86). By the way any reason why we have to have in_ia32_syscall() instead of in_compat_syscall()? > > However I'm not an expert in compat IOCTL code (you are :-) and perhaps you may > > provide ideas better than mine. > > What makes this interface tricky is that this is actually a read() call, not > ioctl() which is usually easier because it encodes the data length in the > command code. As far as I could tell from skimming the interface, the > ioctls are actually fine here. Right. -- With Best Regards, Andy Shevchenko
