From: Andreas Gruenbacher <agruen@suse.de>
To: David Rientjes <rientjes@cs.washington.edu>
Cc: Jesper Juhl <jesper.juhl@gmail.com>,
linux-kernel@vger.kernel.org, Neil Brown <neilb@cse.unsw.edu.au>,
nfs@lists.sourceforge.net, Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH] NFS: nfsaclsvc_encode_getaclres() - Fix potential NULL deref and tiny optimization.
Date: Thu, 2 Nov 2006 16:07:46 +0100 [thread overview]
Message-ID: <200611021607.46373.agruen@suse.de> (raw)
In-Reply-To: <Pine.LNX.4.64N.0610311232190.30578@attu4.cs.washington.edu>
On Tuesday 31 October 2006 21:39, David Rientjes wrote:
> On Tue, 31 Oct 2006, Andreas Gruenbacher wrote:
> > > > w should be an unsigned int.
> > >
> > > Makes sense.
> >
> > No, this breaks the while loop further below: with an unsigned int, the
> > loop counter underflows and wraps.
>
> This is not a problem with w being an unsigned int, it's a problem with
> the while loop. nfsacl_size() returns unsigned int as it should and the
> while loop can be written to respect that since integer division in C
> truncates:
>
> for (n = w / PAGE_SIZE; n > 0; n--)
> if (!rqstp->rq_respages[rqstp->rq_resused++];
Assuming that PAGE_SIZE = 4096 and w = 100, the original loop iterates once,
while your proposed version iterates zero times -- the current code does the
right thing. So the proposed change is still bad, sorry.
Andreas
next prev parent reply other threads:[~2006-11-02 15:07 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-27 21:16 [PATCH] NFS: nfsaclsvc_encode_getaclres() - Fix potential NULL deref and tiny optimization Jesper Juhl
2006-10-27 21:46 ` David Rientjes
2006-10-27 22:01 ` Jesper Juhl
2006-10-31 16:26 ` Andreas Gruenbacher
2006-10-31 16:40 ` Jesper Juhl
2006-10-31 20:39 ` David Rientjes
2006-11-02 15:07 ` Andreas Gruenbacher [this message]
2006-10-31 20:39 ` Small optimization for nfs3acl. (was: Re: [PATCH] NFS: nfsaclsvc_encode_getaclres() - Fix potential NULL deref and tiny optimization.) Jesper Juhl
2006-11-02 15:06 ` Andreas Gruenbacher
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