Messages in this thread | | | Date | Thu, 10 Dec 2009 22:55:14 +0100 | From | "Hans J. Koch" <> | Subject | Re: [patch] drivers: Fix bogus 0 error return in device_add() |
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On Thu, Dec 10, 2009 at 10:01:10PM +0100, Thomas Gleixner wrote: > On Thu, 10 Dec 2009, Greg KH wrote: > > On Thu, Dec 10, 2009 at 07:32:49PM -0000, Thomas Gleixner wrote: > > > If device_add() is called with a device which does not have dev->p set > > > up, then device_private_init() is called. If that succeeds, then the > > > error variable is set to 0. Now if the dev_name(dev) check further > > > down fails, then device_add() correctly terminates, but returns 0. > > > That of course lets the driver progress. If later another driver uses > > > this half set up device as parent then device_add() of the child > > > device explodes and renders sysfs completely unusable. > > > > > > Set the error to -EINVAL if dev_name() check fails. > > > > That's a good catch, thanks. > > > > Is anything currently triggering this? Or did you just find it by > > reading the code? > > Hans-Juergen had a buggy vendor driver where init_name was not > initialized. So the driver probing succeeded and after that a > depending driver crashed somewhere in device_add().
That was one of these USB UDC drivers. It falsely reported OK at probe time and crashed when modprobing a gadget driver. Complete hang of the machine could be achieved by just doing "ls /sys"... Of course, it's the driver's fault not to set init_name, but it's a bit annoying if such mistakes freeze your machine instead of simply producing an error that helps fixing the driver.
Thanks, Hans
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