On Tue, Mar 3, 2026 at 6:18 PM Michel Dänzer <[email protected]> wrote: > > I wrote in my first post in this thread that I don't object to your patch, so > you can relax and stop trying to convince me not to object to it. :) > > I'm just pointing out that this is working around broken user-space code, and > that there are other similar cases where that kind of broken users-space code > couldn't be worked around in the kernel, so it's better to also fix the > user-space code anyway.
At this point I think we're arguing about "how can ioctls be extended" and "does userspace have to use memset" in general, not just about this particular ioctl. You've made the argument that ioctls are not extensible in general unless userspace uses memset. However, I'm not yet convinced of this. As you've also said above, drm_ioctl happily truncates or zero-extends ioctl arguments without returning an error due to size mismatch. Therefore, the only way for userspace to detect if the kernel supports the "extended" ioctl is to add a flag so that the kernel can return an error if it doesn't know the flag. And then that flag could also be used by the kernel to detect which fields of the argument are potentially uninitialized. That is why I asked above if you knew of any other examples where an ioctl was extended and where memset(0) became effectively required due to the extension. > > > -- > Earthling Michel Dänzer \ GNOME / Xwayland / Mesa developer > https://redhat.com \ Libre software enthusiast
