On Wed, Aug 14, 2019 at 07:17:07PM +0200, Knut Omang wrote:
I notice the discussion and your response here: http://linux-kernel.2935.n7.nabble.com/debugfs-and-module-unloading-td865175... I assume that means that protection against module unload while a debugfs file is open is now safe.
It should be, if you set the *owner field of your file_operations properly. Try it and see!
On older kernels, having this code in place is far better than an unprotected debugfs entry/exit - I have tested it extensively in the past :-)
Yes, it seems to work, but again, it really is racy and will fail. Please don't use it.
I perfectly agree with you that reducing the hole for a race condition is generally a bad idea, but from the above mail thread it seems that's the only available choice for older kernels?
I have no idea, but please, do not use that pattern of code as it is racy in all kernels, from all of time.