Re: DoS with POSIX file locks?

Miklos Szeredi
2006-03-20T13:24:11Z

> > > Right. Um. I took it out back in March 2003 after enough people
> > > convinced me it wasn't worth trying to account for all the memory
> > > processes use, and the userbeans project would take care of it anyway.
> > > Haha.
> > >
> > > It's hard to fix the accounting. You have to deal with one thread
> > > allocating the lock, and then a different thread freeing it. We never
> > > actually accounted for posix locks (which are the ones we really needed
> > > to!) and on occasion had current->locks go negative, with all kinds of
> > > associated badness.
> >
> > Things look fairly straightforward if the accounting is done in
> > files_struct instead of task_struct.
>
> that's the wrong place; you can send fd's over unix sockets to other
> processes....

POSIX locks have no association with fd's. Only the inode and the
"owner" is relevant, where owner is derived from the files_struct
pointer for local locks.

Miklos