Re: [PATCH 2/2] driver core: add TAINT_FORCED_BIND for when userspace manually messes with devices and drivers

[Johan Hovold <johan@kernel.org>]

On Wed, Aug 26, 2026 at 11:19:33AM +0200, 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
> successfully 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.
> 
> 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.
> 
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This makes it clear that this is a development tool, and it is a good
compromise preferable to adding unnecessary complexity or suppressing
the attributes completely just to prevent root from shooting themselves
in the foot:

Reviewed-by: Johan Hovold <johan@kernel.org>
Tested-by: Johan Hovold <johan@kernel.org>

Johan