Re: DoS with POSIX file locks?

[Arjan van de Ven]

On Mon, 2006-03-20 at 13:52 +0100, Miklos Szeredi wrote:
> > 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....



the better solution is to account per user struct, and keep a pointer
(and a refcount) of that user struct inside your lock data somehow.


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