Re: linux-next NFSD: NULL pointer dereference at nfsd_svc()

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On Tue, Aug 03, 2010 at 11:48:51AM -0400, J. Bruce Fields wrote:
> On Tue, Aug 03, 2010 at 10:09:03AM +0900, Tetsuo Handa wrote:
> > Hello.
> > 
> > That patch solved the NULL pointer dereference problem. Thank you.
> > 
> > But I got another problem. After applying that patch on 2.6.35-next-20100802 ,
> > mount operation fails with timeout error.
> 
> Argh, yes, problem found, I think--I'll do some more testing and send
> you another attempt....

How about this?

(By the way, are you using something other than the standard
/etc/init.d/nfs-kernel-server to start/stop the server?  Or have you
customized your installation in any way?  Just curious, as the bugs
you're finding are good, but I'd expect different symptoms from the
default setup.)

--b.

commit 3deb279d6e5625407919a875db3a2461199566b3
Author: J. Bruce Fields <bfields@xxxxxxxxxx>
Date:   Mon Aug 2 14:12:44 2010 -0400

    nfsd: fix startup/shutdown order bug
    
    We must create the server before we can call init_socks or check the
    number of threads.
    
    Symptoms were a NULL pointer dereference in nfsd_svc().  Problem
    identified by Jeff Layton.
    
    Reported-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>

diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 92173bd..58e3d4c 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -420,7 +420,7 @@ int
 nfsd_svc(unsigned short port, int nrservs)
 {
 	int	error;
-	bool	first_thread;
+	bool	unstarted, first_thread;
 
 	mutex_lock(&nfsd_mutex);
 	dprintk("nfsd: creating service\n");
@@ -432,29 +432,31 @@ nfsd_svc(unsigned short port, int nrservs)
 	if (nrservs == 0 && nfsd_serv == NULL)
 		goto out;
 
-	first_thread = (nfsd_serv->sv_nrthreads == 0) && (nrservs != 0);
+	unstarted = nfsd_serv == NULL || nfsd_serv->sv_nrthreads == 0;
+	first_thread = unstarted && (nrservs != 0);
+
+	error = nfsd_create_serv();
+	if (error)
+		goto out;
 
 	if (first_thread) {
 		error = nfsd_startup(port, nrservs);
 		if (error)
-			goto out;
+			goto out_destroy;
 	}
-	error = nfsd_create_serv();
-	if (error)
-		goto out_shutdown;
 	error = svc_set_num_threads(nfsd_serv, NULL, nrservs);
 	if (error)
-		goto out_destroy;
+		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;
-out_destroy:
-	svc_destroy(nfsd_serv);		/* Release server */
 out_shutdown:
 	if (error < 0 && first_thread)
 		nfsd_shutdown();
+out_destroy:
+	svc_destroy(nfsd_serv);		/* Release server */
 out:
 	mutex_unlock(&nfsd_mutex);
 	return error;
--
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