Re: [syzbot] [nfs?] INFO: task hung in nfsd_nl_listener_set_doit

[Edward Adam Davis]

#syz test

diff --git a/include/net/genetlink.h b/include/net/genetlink.h
index 9ab49bfeae78..51c4e811c01c 100644
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -137,6 +137,7 @@ struct genl_info {
 	possible_net_t		_net;
 	void *			user_ptr[2];
 	struct netlink_ext_ack *extack;
+	struct mutex		fslock;
 };
 
 static inline struct net *genl_info_net(const struct genl_info *info)
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index feb54c63a116..abf52285e26a 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -1105,6 +1105,7 @@ static int genl_family_rcv_msg_doit(const struct genl_family *family,
 	info.extack = extack;
 	genl_info_net_set(&info, net);
 	memset(&info.user_ptr, 0, sizeof(info.user_ptr));
+	mutex_init(&info.fslock);
 
 	if (ops->pre_doit) {
 		err = ops->pre_doit(ops, skb, &info);
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 34eb2c2cbcde..8d0ac4f699bd 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1953,11 +1953,11 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info)
 	struct nfsd_net *nn;
 	int err, rem;
 
-	mutex_lock(&nfsd_mutex);
+	mutex_lock(&info->fslock);
 
 	err = nfsd_create_serv(net);
 	if (err) {
-		mutex_unlock(&nfsd_mutex);
+		mutex_unlock(&info->fslock);
 		return err;
 	}
 
@@ -2080,7 +2080,7 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info)
 		nfsd_destroy_serv(net);
 
 out_unlock_mtx:
-	mutex_unlock(&nfsd_mutex);
+	mutex_unlock(&info->fslock);
 
 	return err;
 }
@@ -2110,7 +2110,7 @@ int nfsd_nl_listener_get_doit(struct sk_buff *skb, struct genl_info *info)
 		goto err_free_msg;
 	}
 
-	mutex_lock(&nfsd_mutex);
+	mutex_lock(&info->fslock);
 	nn = net_generic(genl_info_net(info), nfsd_net_id);
 
 	/* no nfs server? Just send empty socket list */
@@ -2141,14 +2141,14 @@ int nfsd_nl_listener_get_doit(struct sk_buff *skb, struct genl_info *info)
 	}
 	spin_unlock_bh(&serv->sv_lock);
 out_unlock_mtx:
-	mutex_unlock(&nfsd_mutex);
+	mutex_unlock(&info->fslock);
 	genlmsg_end(skb, hdr);
 
 	return genlmsg_reply(skb, info);
 
 err_serv_unlock:
 	spin_unlock_bh(&serv->sv_lock);
-	mutex_unlock(&nfsd_mutex);
+	mutex_unlock(&info->fslock);
 err_free_msg:
 	nlmsg_free(skb);