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SubjectRe: [PATCH v3] NFSd: set nfsd_serv to NULL after service destruction
On Tue, Jul 03, 2012 at 04:46:41PM +0400, Stanislav Kinsbursky wrote:
> v3:
> 1) Rebased for 3.6 kernel.
>
> v2:
> 1) Set global nfsd_serv pointer to NULL only if no running threads left.
>
> Otherwise we will get NULL pointer dereference on last thread exit in
> nfsd_last_thread().
> This patch also introduces nfsd_destroy() helper for per-net NFSd shutdown.

That last step should really be done in a separate patch, then the
bugfix done after that.

But I'm confused: I'm not seeing the NULL dereference.
nfsd_last_thread doesn't use nfsd_serv as far as I can tell.

--b.

>
> Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
> ---
> fs/nfsd/nfsctl.c | 8 ++------
> fs/nfsd/nfsd.h | 11 +++++++++++
> fs/nfsd/nfssvc.c | 24 ++++++++----------------
> 3 files changed, 21 insertions(+), 22 deletions(-)
>
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index c55298e..fa49cff 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -673,9 +673,7 @@ static ssize_t __write_ports_addfd(char *buf)
>
> err = svc_addsock(nfsd_serv, fd, buf, SIMPLE_TRANSACTION_LIMIT);
> if (err < 0) {
> - if (nfsd_serv->sv_nrthreads == 1)
> - svc_shutdown_net(nfsd_serv, net);
> - svc_destroy(nfsd_serv);
> + nfsd_destroy(net);
> return err;
> }
>
> @@ -744,9 +742,7 @@ out_close:
> svc_xprt_put(xprt);
> }
> out_err:
> - if (nfsd_serv->sv_nrthreads == 1)
> - svc_shutdown_net(nfsd_serv, net);
> - svc_destroy(nfsd_serv);
> + nfsd_destroy(net);
> return err;
> }
>
> diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
> index 1671429..1336a65 100644
> --- a/fs/nfsd/nfsd.h
> +++ b/fs/nfsd/nfsd.h
> @@ -73,6 +73,17 @@ int nfsd_nrpools(void);
> int nfsd_get_nrthreads(int n, int *);
> int nfsd_set_nrthreads(int n, int *);
>
> +static inline void nfsd_destroy(struct net *net)
> +{
> + int destroy = (nfsd_serv->sv_nrthreads == 1);
> +
> + if (destroy)
> + svc_shutdown_net(nfsd_serv, net);
> + svc_destroy(nfsd_serv);
> + if (destroy)
> + nfsd_serv = NULL;
> +}
> +
> #if defined(CONFIG_NFSD_V2_ACL) || defined(CONFIG_NFSD_V3_ACL)
> #ifdef CONFIG_NFSD_V2_ACL
> extern struct svc_version nfsd_acl_version2;
> diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
> index ee709fc..240473c 100644
> --- a/fs/nfsd/nfssvc.c
> +++ b/fs/nfsd/nfssvc.c
> @@ -254,8 +254,6 @@ static void nfsd_shutdown(void)
>
> static void nfsd_last_thread(struct svc_serv *serv, struct net *net)
> {
> - /* When last nfsd thread exits we need to do some clean-up */
> - nfsd_serv = NULL;
> nfsd_shutdown();
>
> svc_rpcb_cleanup(serv, net);
> @@ -332,6 +330,7 @@ static int nfsd_get_default_max_blksize(void)
> int nfsd_create_serv(void)
> {
> int error;
> + struct net *net = current->nsproxy->net_ns;
>
> WARN_ON(!mutex_is_locked(&nfsd_mutex));
> if (nfsd_serv) {
> @@ -346,7 +345,7 @@ int nfsd_create_serv(void)
> if (nfsd_serv == NULL)
> return -ENOMEM;
>
> - error = svc_bind(nfsd_serv, current->nsproxy->net_ns);
> + error = svc_bind(nfsd_serv, net);
> if (error < 0) {
> svc_destroy(nfsd_serv);
> return error;
> @@ -427,11 +426,7 @@ int nfsd_set_nrthreads(int n, int *nthreads)
> if (err)
> break;
> }
> -
> - if (nfsd_serv->sv_nrthreads == 1)
> - svc_shutdown_net(nfsd_serv, net);
> - svc_destroy(nfsd_serv);
> -
> + nfsd_destroy(net);
> return err;
> }
>
> @@ -478,9 +473,7 @@ 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 */
> + nfsd_destroy(net); /* Release server */
> out:
> mutex_unlock(&nfsd_mutex);
> return error;
> @@ -563,12 +556,13 @@ nfsd(void *vrqstp)
> nfsdstats.th_cnt --;
>
> out:
> - if (rqstp->rq_server->sv_nrthreads == 1)
> - svc_shutdown_net(rqstp->rq_server, &init_net);
> + rqstp->rq_server = NULL;
>
> /* Release the thread */
> svc_exit_thread(rqstp);
>
> + nfsd_destroy(&init_net);
> +
> /* Release module */
> mutex_unlock(&nfsd_mutex);
> module_put_and_exit(0);
> @@ -682,9 +676,7 @@ int nfsd_pool_stats_release(struct inode *inode, struct file *file)
>
> mutex_lock(&nfsd_mutex);
> /* this function really, really should have been called svc_put() */
> - if (nfsd_serv->sv_nrthreads == 1)
> - svc_shutdown_net(nfsd_serv, net);
> - svc_destroy(nfsd_serv);
> + nfsd_destroy(net);
> mutex_unlock(&nfsd_mutex);
> return ret;
> }
>


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