On Thu, Mar 31, 2022 at 03:52:14PM +0300, Heikki Krogerus wrote: > Hi Greg, > > On Thu, Mar 31, 2022 at 01:39:51PM +0200, Greg KH wrote: > > On Thu, Mar 31, 2022 at 12:25:43PM +0300, Heikki Krogerus wrote: > > > On Thu, Mar 31, 2022 at 11:12:55AM +0200, Takashi Iwai wrote: > > > > > > > - if (!strcmp(dev->driver->name, "i915") && > > > > > > > + if (dev->driver && !strcmp(dev->driver->name, "i915") && > > > > > > > > > > > > Can NULL dev->driver be really seen? I thought the components are > > > > > > added by the drivers, hence they ought to have the driver field set. > > > > > > But there can be corner cases I overlooked. > > > > > > > > > > > > > > > > > > thanks, > > > > > > > > > > > > Takashi > > > > > > > > > > Hi Takashi, > > > > > > > > > > When I try using component_add in a different driver (usb4 in my > > > > > case), I think dev->driver here is NULL because the i915 drivers do > > > > > not have their component master fully bound when this new component is > > > > > registered. When I test it, it seems to be causing a crash. > > > > > > > > Hm, from where component_add*() is called? Basically dev->driver must > > > > be already set before the corresponding driver gets bound at > > > > __driver_probe_deviec(). So, if the device is added to component from > > > > the corresponding driver's probe, dev->driver must be non-NULL. > > > > > > The code that declares a device as component does not have to be the > > > driver of that device. > > > > > > In our case the components are USB ports, and they are devices that > > > are actually never bind to any drivers: drivers/usb/core/port.c > > > > Why is a USB device being passed to this code that assumes it is looking > > for a PCI device with a specific driver name? As I mentioned on the > > mei patch, triggering off of a name is really a bad idea, as is assuming > > the device type without any assurance it is such a device (there's a > > reason we didn't provide device type identification in the driver core, > > don't abuse that please...) > > I totally agree. This driver is making a whole bunch of assumptions > when it should not make any assumptions. And yes, one of those > assumptions is that the driver of the device has a specific name, and > that is totally crazy. So why is it making those assumptions? I have > no idea, but is does, and they are now causing the first problem - > NULL pointer dereference. > > This patch (and that other) is only proposing a simple way to solve > that NULL pointer dereference issue by adding some sanity checks. If > that's no OK, and the whole driver should be refactored instead, then > that is perfectly OK by me, but that has to be done by somebody who > understands what exactly is the driver and the device it's controlling > doing (and for). This all needs to be refactored to not do this at all. thanks, greg k-h
