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    SubjectRe: [CRAZY-RFF] debugfs: track open files and release on remove
    On Fri, Oct 09, 2020 at 10:19:02AM +0200, Johannes Berg wrote:
    > On Fri, 2020-10-09 at 10:16 +0200, Greg KH wrote:
    > > On Fri, Oct 09, 2020 at 10:06:14AM +0200, Johannes Berg wrote:
    > > > We used to say the proxy_fops weren't needed and it wasn't an issue, and
    > > > then still implemented it. Dunno. I'm not really too concerned about it
    > > > myself, only root can hold the files open and remove modules ...
    > >
    > > proxy_fops were needed because devices can be removed from the system at
    > > any time, causing their debugfs files to want to also be removed. It
    > > wasn't because of unloading kernel code.
    >
    > Indeed, that's true. Still, we lived with it for years.

    Because no one wanted to fix the code, not because it was correct :)

    > Anyway, like I said, I really just did this more to see that it _could_
    > be done, not to suggest that it _should_ :-)

    Agreed.

    > I think adding the .owner everywhere would be good, and perhaps we can
    > somehow put a check somewhere like
    >
    > WARN_ON(is_module_address((unsigned long)fops) && !fops->owner);
    >
    > to prevent the issue in the future?

    That will fail for all of the debugfs_create_* operations, as there is
    only one set of file operations for all of the different files created
    with these calls.

    Which, now that I remember it, is why we went down the proxy "solution"
    in the first place :(

    thanks,

    greg k-h

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