Re: Flaw in the driver-model implementation of attributes

From: Jeremy Fitzhardinge (
Date: Sun Jun 15 2003 - 12:40:45 EST

On Sun, 2003-06-15 at 09:42, Alan Stern wrote:
> If you're already aware of this, please forgive the intrusion.
> There's a general problem in the driver model's implementation of
> attribute files, in connection with loadable kernel modules. The
> sysfs_ops structure stores function pointers with no means for identifying
> the module that contains the corresponding code. As a result, it's
> possible to call through one of these pointers even after the module has
> been unloaded, causing an oops.
> It's not hard to provoke this sort of situation. A user process can
> open a sysfs device file, for instance, and delay trying to read it until
> the module containing the device driver has been removed. When the read
> does occur, it runs into trouble.

I've seen this oops when a program has its cwd in a /sys directory
corresponding to a removed (or replaced) module. I think active
references to a part of the /sys namespace corresponding to a module
should just pin the module. But I haven't looked into it really.

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This archive was generated by hypermail 2b29 : Sun Jun 15 2003 - 22:00:42 EST