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

[Uwe Kleine-König]

On Wed, Oct 28, 2026 at 02:42:15PM +0100, Greg Kroah-Hartman wrote:
> This reverts commit fcbfaffee51a452cc8efcbaa3b88ec4595678424.
> 
> Turns out that vfio is a crazy beast and people have been "relying" on
> the bind/unbind debugging feature as a way to handle passing through
> devices to guest instances.  Because of this (https://xkcd.com/1172/),
> let's revert the feature for now until we can figure out a more agreable
> way to handle this such that normal workflows do not taint the kernel.
> 
> Odds are something like what Uwe proposes at:
> 	https://lore.kernel.org/lkml/cover.1790612298.git.u.kleine-koenig@xxxxxxxxxxxx/
> will be the best way forward and will be revisited after for after 7.4.
> 
> The feature was originally intended to stem the flow of unnecessary
> fuzzing reports of "broken" drivers where random devices were being
> bound to random drivers and of course things were going wrong.  The main
> syzbot tool is now not doing this anymore, and hopefully no one else
> starts it up again (but in this madness of LLMs these days, you can't be
> sure.)
> 
> Thanks to everyone for telling me just how wrong I was to implement
> this, I appreciated the feedback :)
> 
> Link: https://lore.kernel.org/all/DLIL9H50MALI.3JROXYEEUM3KU@xxxxxxxxxx/
> To: Jonathan Corbet <corbet@xxxxxxx>
> To: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
> To: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> To: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
> To: Danilo Krummrich <dakr@xxxxxxxxxx>
> To: Johan Hovold <johan@xxxxxxxxxx>
> To: Steven Rostedt <rostedt@xxxxxxxxxxx>
> To: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> To: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> Reported-by: Leon Romanovsky <leon@xxxxxxxxxx>
> Reported-by: Jason Gunthorpe <jgg@xxxxxxxx>
> Reported-by: Michal Pecio <michal.pecio@xxxxxxxxx>
> Reported-by: "Uwe Kleine-König" <u.kleine-koenig@xxxxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
>  Documentation/admin-guide/tainted-kernels.rst | 52 +++++++++++++--------------
>  drivers/base/bus.c                            |  3 --
>  include/linux/panic.h                         |  3 +-
>  include/trace/events/module.h                 |  3 +-
>  kernel/panic.c                                |  5 ++-
>  tools/debugging/kernel-chktaint               |  8 -----
>  6 files changed, 28 insertions(+), 46 deletions(-)
> 
> diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst
> index a208811ad525..3d312bc17942 100644
> --- a/Documentation/admin-guide/tainted-kernels.rst
> +++ b/Documentation/admin-guide/tainted-kernels.rst

It's not part of commit fcbfaffee51a452cc8efcbaa3b88ec4595678424, but
conceptually we need 

diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst
index 3d312bc17942..fcb8b9734548 100644
--- a/Documentation/admin-guide/tainted-kernels.rst
+++ b/Documentation/admin-guide/tainted-kernels.rst
@@ -74,7 +74,7 @@ a particular type of taint. It's best to leave that to the aforementioned
 script, but if you need something quick you can use this shell command to check
 which bits are set::
 
-	$ for i in $(seq 0 20); do echo $i $(($(cat /proc/sys/kernel/tainted)>>$i&1));done
+	$ for i in $(seq 0 19); do echo $i $(($(cat /proc/sys/kernel/tainted)>>$i&1));done
 
 Table for decoding tainted state
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

in this change which was fixed in commit f1850e443b0e ("docs:
admin-guide: Handle TAINT_FORCED_BIND when parsing
/proc/sys/kernel/tainted"), but that commit shouldn't be reverted as it
contains a simplification that we should keep.

Best regards
Uwe

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