[PATCH 6.1.y 5/7] nfsd: drop the nfsd_put helper

[cel@xxxxxxxxxx]

From: Jeff Layton <jlayton@xxxxxxxxxx>

[ Upstream commit 64e6304169f1e1f078e7f0798033f80a7fb0ea46 ]

It's not safe to call nfsd_put once nfsd_last_thread has been called, as
that function will zero out the nn->nfsd_serv pointer.

Drop the nfsd_put helper altogether and open-code the svc_put in its
callers instead. That allows us to not be reliant on the value of that
pointer when handling an error.

Fixes: 2a501f55cd64 ("nfsd: call nfsd_last_thread() before final nfsd_put()")
Reported-by: Zhi Li <yieli@xxxxxxxxxx>
Cc: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Jeffrey Layton <jlayton@xxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
 fs/nfsd/nfsctl.c | 31 +++++++++++++++++--------------
 fs/nfsd/nfsd.h   |  7 -------
 2 files changed, 17 insertions(+), 21 deletions(-)

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index a906d0257e3a..2feaa49fb9fe 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -709,6 +709,7 @@ static ssize_t __write_ports_addfd(char *buf, struct net *net, const struct cred
 	char *mesg = buf;
 	int fd, err;
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+	struct svc_serv *serv;
 
 	err = get_int(&mesg, &fd);
 	if (err != 0 || fd < 0)
@@ -718,15 +719,15 @@ static ssize_t __write_ports_addfd(char *buf, struct net *net, const struct cred
 	if (err != 0)
 		return err;
 
-	err = svc_addsock(nn->nfsd_serv, net, fd, buf, SIMPLE_TRANSACTION_LIMIT, cred);
+	serv = nn->nfsd_serv;
+	err = svc_addsock(serv, net, fd, buf, SIMPLE_TRANSACTION_LIMIT, cred);
 
-	if (err < 0 && !nn->nfsd_serv->sv_nrthreads && !nn->keep_active)
+	if (err < 0 && !serv->sv_nrthreads && !nn->keep_active)
 		nfsd_last_thread(net);
-	else if (err >= 0 &&
-		 !nn->nfsd_serv->sv_nrthreads && !xchg(&nn->keep_active, 1))
-		svc_get(nn->nfsd_serv);
+	else if (err >= 0 && !serv->sv_nrthreads && !xchg(&nn->keep_active, 1))
+		svc_get(serv);
 
-	nfsd_put(net);
+	svc_put(serv);
 	return err;
 }
 
@@ -740,6 +741,7 @@ static ssize_t __write_ports_addxprt(char *buf, struct net *net, const struct cr
 	struct svc_xprt *xprt;
 	int port, err;
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+	struct svc_serv *serv;
 
 	if (sscanf(buf, "%15s %5u", transport, &port) != 2)
 		return -EINVAL;
@@ -751,32 +753,33 @@ static ssize_t __write_ports_addxprt(char *buf, struct net *net, const struct cr
 	if (err != 0)
 		return err;
 
-	err = svc_xprt_create(nn->nfsd_serv, transport, net,
+	serv = nn->nfsd_serv;
+	err = svc_xprt_create(serv, transport, net,
 			      PF_INET, port, SVC_SOCK_ANONYMOUS, cred);
 	if (err < 0)
 		goto out_err;
 
-	err = svc_xprt_create(nn->nfsd_serv, transport, net,
+	err = svc_xprt_create(serv, transport, net,
 			      PF_INET6, port, SVC_SOCK_ANONYMOUS, cred);
 	if (err < 0 && err != -EAFNOSUPPORT)
 		goto out_close;
 
-	if (!nn->nfsd_serv->sv_nrthreads && !xchg(&nn->keep_active, 1))
-		svc_get(nn->nfsd_serv);
+	if (!serv->sv_nrthreads && !xchg(&nn->keep_active, 1))
+		svc_get(serv);
 
-	nfsd_put(net);
+	svc_put(serv);
 	return 0;
 out_close:
-	xprt = svc_find_xprt(nn->nfsd_serv, transport, net, PF_INET, port);
+	xprt = svc_find_xprt(serv, transport, net, PF_INET, port);
 	if (xprt != NULL) {
 		svc_xprt_close(xprt);
 		svc_xprt_put(xprt);
 	}
 out_err:
-	if (!nn->nfsd_serv->sv_nrthreads && !nn->keep_active)
+	if (!serv->sv_nrthreads && !nn->keep_active)
 		nfsd_last_thread(net);
 
-	nfsd_put(net);
+	svc_put(serv);
 	return err;
 }
 
diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
index 781781b88cca..996f3f62335b 100644
--- a/fs/nfsd/nfsd.h
+++ b/fs/nfsd/nfsd.h
@@ -97,13 +97,6 @@ int		nfsd_pool_stats_open(struct inode *, struct file *);
 int		nfsd_pool_stats_release(struct inode *, struct file *);
 void		nfsd_shutdown_threads(struct net *net);
 
-static inline void nfsd_put(struct net *net)
-{
-	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
-
-	svc_put(nn->nfsd_serv);
-}
-
 bool		i_am_nfsd(void);
 
 struct nfsdfs_client {
-- 
2.45.1