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SubjectRe: bug in count_open_files() or a strange granularity?
Hi Alexander,

Thank you for the useful comments.

On Tue, 28 Nov 2000, Alexander Viro wrote:
> On Tue, 28 Nov 2000, Tigran Aivazian wrote:
>
> > /* switch the open fds from old_user to new_user */
> > read_lock(&files->file_lock);
> > nr_open = close_files(files, 0); /* 0 means don't close them */
> > atomic_sub(nr_open, &old_user->files);
> > atomic_add(nr_open, &new_user->files);
> > read_unlock(&files->file_lock);
>
> That makes no sense - how do you count the descriptors in shared ->files?
> And how on the Earth do you count SCM_RIGHTS packets? Because they make
> a great way to fool any use of that stuff for resource-limit type of
> applications (stash the descriptors into SCM_RIGHTS cookie, send them to
> yourself and close them).

Yes, both the shared file struct and the SCM_RIGHTS are not so easy to
account. I never said this is ready -- just work in progress. If you have
already done this, please let me know -- there is plenty of other things
to do and I don't wish to step on your toes.

>
> Basically, I don't see what are you counting.
¬¬¬¬¬¬¬¬¬

it is not basic at all. The problems you point out are extremely complex
(at least the fd in transit issue, definitely is).

So, yes it requires a bit more thought. I will come back when the issues
you pointed out are dealt with. Someone has added the 'files' field to the
'struct user_struct' so someone must have meant to put support for this
field to be something other than the meaningless 0 it currently is.

Regards,
Tigran

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