To: bfields@fieldses.org
CC: matthew@wil.cx, linux-fsdevel@vger.kernel.org,
       linux-kernel@vger.kernel.org
In-reply-to: <20060320203556.GC31512@fieldses.org> (bfields@fieldses.org)
Subject: Re: DoS with POSIX file locks?
References: <E1FLIlF-0007zR-00@dorka.pomaz.szeredi.hu> <20060320121107.GE8980@parisc-linux.org> <E1FLJLs-00085u-00@dorka.pomaz.szeredi.hu> <20060320123950.GF8980@parisc-linux.org> <E1FLJsF-0008A7-00@dorka.pomaz.szeredi.hu> <20060320153202.GH8980@parisc-linux.org> <E1FLNRi-0000We-00@dorka.pomaz.szeredi.hu> <20060320203556.GC31512@fieldses.org>
Message-Id: <E1FLaW8-0001hD-00@dorka.pomaz.szeredi.hu>
From: Miklos Szeredi <miklos@szeredi.hu>
Date: Tue, 21 Mar 2006 07:38:56 +0100
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1037
Lines: 25

> > > > Things look fairly straightforward if the accounting is done in
> > > > files_struct instead of task_struct.  At least for POSIX locks.  I
> > > > haven't looked at flocks or leases yet.
> > > 
> > > I was thinking that would work, yes.  It might not be worth worrying
> > > about accounting for leases/flocks since each process can only have one
> > > of those per open file anyway.
> > 
> > Here's a minimally tested patch.  The only tricky part is when the
> > unlock splits an existing lock in two.
> > 
> > Also the limit checking is sloppy when the lock is split, and in that
> > case allows the counter to go one above the limit.
> 
> Do you need to handle blocks as well as applied locks?

I don't think so, because each task may only have at most one block at
a time.

Miklos
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