Re: [PATCH] [RFC] nfsd: fix possible dereference of static NULL nfsd_servpointer

[Stanislav Kinsbursky]

06.07.2012 21:26, J. Bruce Fields ÐÐÑÐÑ:
> On Fri, Jul 06, 2012 at 05:45:56PM +0400, Stanislav Kinsbursky wrote:
> > This is a bug fix for 3.5 kernel.
> > In case on NFSd service start failure svc_shutdown_net() will call svc_destroy
> > callback and zeroize global nfsd_serv pointer, this in turn will lead to Oops
> > in svc_destroy().
> >
> > This patch is marked as RFC, because to many lines were changed. It can be
> > easely simplified if requested.
> > Moreover, NFSd service shutdown is going to be converted into csomething on
> > per-net basis.
> Doesn't this leave error paths in e.g. __write_ports_addfd() and
> __write_ports_addxprt() unfixed?

Yes, sure it does...

> I'm inclined to just submit your original fix (split up as in the last
> version I sent) for 3.5 if you don't object.

Not at all.
Thanks, Bruce.

> --b.
>
> > Signed-off-by: Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx>
> > ---
> >   fs/nfsd/nfssvc.c |   14 ++++++++------
> >   1 files changed, 8 insertions(+), 6 deletions(-)
> >
> > diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
> > index ee709fc..526a4aa 100644
> > --- a/fs/nfsd/nfssvc.c
> > +++ b/fs/nfsd/nfssvc.c
> > @@ -446,6 +446,7 @@ nfsd_svc(unsigned short port, int nrservs)
> >   	int	error;
> >   	bool	nfsd_up_before;
> >   	struct net *net = &init_net;
> > +	struct svc_serv *serv = nfsd_serv;
> >   
> >   	mutex_lock(&nfsd_mutex);
> >   	dprintk("nfsd: creating service\n");
> > @@ -454,7 +455,7 @@ nfsd_svc(unsigned short port, int nrservs)
> >   	if (nrservs > NFSD_MAXSERVS)
> >   		nrservs = NFSD_MAXSERVS;
> >   	error = 0;
> > -	if (nrservs == 0 && nfsd_serv == NULL)
> > +	if (nrservs == 0 && serv == NULL)
> >   		goto out;
> >   
> >   	error = nfsd_create_serv();
> > @@ -464,23 +465,24 @@ nfsd_svc(unsigned short port, int nrservs)
> >   	nfsd_up_before = nfsd_up;
> >   
> >   	error = nfsd_startup(port, nrservs);
> > +	error = -EINVAL;
> >   	if (error)
> >   		goto out_destroy;
> > -	error = svc_set_num_threads(nfsd_serv, NULL, nrservs);
> > +	error = svc_set_num_threads(serv, NULL, nrservs);
> >   	if (error)
> >   		goto out_shutdown;
> >   	/* We are holding a reference to nfsd_serv which
> >   	 * we don't want to count in the return value,
> >   	 * so subtract 1
> >   	 */
> > -	error = nfsd_serv->sv_nrthreads - 1;
> > +	error = serv->sv_nrthreads - 1;
> >   out_shutdown:
> >   	if (error < 0 && !nfsd_up_before)
> >   		nfsd_shutdown();
> >   out_destroy:
> > -	if (nfsd_serv->sv_nrthreads == 1)
> > -		svc_shutdown_net(nfsd_serv, net);
> > -	svc_destroy(nfsd_serv);		/* Release server */
> > +	if (serv->sv_nrthreads == 1)
> > +		svc_shutdown_net(serv, net);
> > +	svc_destroy(serv);		/* Release server */
> >   out:
> >   	mutex_unlock(&nfsd_mutex);
> >   	return error;


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