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SubjectRe: [PATCH v2 2/6] driver core: Add common support to skip probe for un-authorized devices
On Thu, Sep 30, 2021 at 11:32:41AM -0400, Alan Stern wrote:
> On Thu, Sep 30, 2021 at 10:48:54AM -0400, Michael S. Tsirkin wrote:
> > On Thu, Sep 30, 2021 at 10:43:05AM -0400, Alan Stern wrote:
> > > I don't see any point in talking about "untrusted drivers". If a
> > > driver isn't trusted then it doesn't belong in your kernel. Period.
> > > When you load a driver into your kernel, you are implicitly trusting
> > > it (aside from limitations imposed by security modules). The code
> > > it contains, the module_init code in particular, runs with full
> > > superuser permissions.
> > >
> > > What use is there in loading a driver but telling the kernel "I don't
> > > trust this driver, so don't allow it to probe any devices"? Why not
> > > just blacklist it so that it never gets modprobed in the first place?
> > >
> > > Alan Stern
> >
> > When the driver is built-in, it seems useful to be able to block it
> > without rebuilding the kernel. This is just flipping it around
> > and using an allow-list for cases where you want to severly
> > limit the available functionality.
>
> Does this make sense?
>
> The only way to tell the kernel to block a built-in driver is by
> using some boot-command-line option. Otherwise the driver's init
> code will run before you have a chance to tell the kernel anything at
> all.
>
> So if you change your mind about whether a driver should be blocked,
> all you have to do is remove the blocking option from the command
> line and reboot. No kernel rebuild is necessary.
>
> Alan Stern

Right.

--
MST

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