On Fri, Sep 18, 2026 at 06:39:02PM +0200, Danilo Krummrich wrote: > On Mon Sep 14, 2026 at 4:30 PM CEST, Greg Kroah-Hartman wrote: > > The ability to add and remove devices from a driver through the sysfs > > "bind" and "unbind" files was created all those decades ago as a way > > that kernel developers can iterate faster, and provide a debugging way > > for users to attempt to add a new device to a driver without having to > > rebuild their kernel. > > > > This api over the years has been abused and recently come under a major > > fuzzing "attack" through tools like syzbot which decided that it would > > attempt to just randomly bind any driver to any type of device, causing > > loads of unneeded errors and pointless kernel patches to be generated by > > unsuspecting new developers. > > > > Handle all of this by adding a new taint flag, TAINT_FORCED_BIND, which > > will be set on the driver if the bind/unbind sysfs files are ever > > written to. This lets kernel developers "know" that a user is > > attempting to do something that is not normal, and as such, if the > > kernel breaks they get to keep the shiny pieces laying around on the > > floor. > > > > The flag is 'Y' which was unused, and can remembered as the user is > > "yeeting" the device being operated on here (thrown with force without > > regard for the thing being thrown). > > > > Note, the taint flag gets set _BEFORE_ the bind/unbind callback happens, > > as many times crashes/oops/warnings/failures happen within the callback, > > and the taint flag needs to be there to show what was being attempted. > > If it were to be set after the callback happens, the oops report would > > not properly reflect what foolishness was being attempted. > > > > Fuzzing tools like syzbot, that doesn't have hand-crafted rules to keep > > the tool from hitting bind/unbind, should be run with panic_on_taint > > enabled so that they fall over and don't continue on, thinking that they > > actually found a real issue. > > > > Userspace operations that rely on the bind/unbind files > > I agree that this should be avoided. > > But I also think the biggest offender really is driver_override. Specifically, > on a hot-pluggable bus a driver must be complient with the device driver > lifecycle rules and hence shouldn't break on bind/unbind. I think it would be > nice to not taint the kernel for such busses, and only taint on > driver_override, > as I think we'd still want the bug reports for such cases. > > But I think this is fine to leave for a follow-up.
Yeah, let's see how this goes, thanks for the review! greg k-h
