Merge branch 'tun-races'

Eric Dumazet says:

====================
tun: address two syzbot reports

Small changes addressing races discovered by syzbot.

First patch is a cleanup.
Second patch moves a mutex init sooner.
Third patch makes sure each tfile gets its own napi enable flags.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/tun.c

@@ -181,6 +181,7 @@ struct tun_file {
 	};
 	struct napi_struct napi;
 	bool napi_enabled;
+	bool napi_frags_enabled;
 	struct mutex napi_mutex;	/* Protects access to the above napi */
 	struct list_head next;
 	struct tun_struct *detached;
@@ -313,32 +314,32 @@ static int tun_napi_poll(struct napi_struct *napi, int budget)
 }
 
 static void tun_napi_init(struct tun_struct *tun, struct tun_file *tfile,
-			  bool napi_en)
+			  bool napi_en, bool napi_frags)
 {
 	tfile->napi_enabled = napi_en;
+	tfile->napi_frags_enabled = napi_en && napi_frags;
 	if (napi_en) {
 		netif_napi_add(tun->dev, &tfile->napi, tun_napi_poll,
 			       NAPI_POLL_WEIGHT);
 		napi_enable(&tfile->napi);
-		mutex_init(&tfile->napi_mutex);
 	}
 }
 
-static void tun_napi_disable(struct tun_struct *tun, struct tun_file *tfile)
+static void tun_napi_disable(struct tun_file *tfile)
 {
 	if (tfile->napi_enabled)
 		napi_disable(&tfile->napi);
 }
 
-static void tun_napi_del(struct tun_struct *tun, struct tun_file *tfile)
+static void tun_napi_del(struct tun_file *tfile)
 {
 	if (tfile->napi_enabled)
 		netif_napi_del(&tfile->napi);
 }
 
-static bool tun_napi_frags_enabled(const struct tun_struct *tun)
+static bool tun_napi_frags_enabled(const struct tun_file *tfile)
 {
-	return READ_ONCE(tun->flags) & IFF_NAPI_FRAGS;
+	return tfile->napi_frags_enabled;
 }
 
 #ifdef CONFIG_TUN_VNET_CROSS_LE
@@ -690,8 +691,8 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
 	tun = rtnl_dereference(tfile->tun);
 
 	if (tun && clean) {
-		tun_napi_disable(tun, tfile);
-		tun_napi_del(tun, tfile);
+		tun_napi_disable(tfile);
+		tun_napi_del(tfile);
 	}
 
 	if (tun && !tfile->detached) {
@@ -758,7 +759,7 @@ static void tun_detach_all(struct net_device *dev)
 	for (i = 0; i < n; i++) {
 		tfile = rtnl_dereference(tun->tfiles[i]);
 		BUG_ON(!tfile);
-		tun_napi_disable(tun, tfile);
+		tun_napi_disable(tfile);
 		tfile->socket.sk->sk_shutdown = RCV_SHUTDOWN;
 		tfile->socket.sk->sk_data_ready(tfile->socket.sk);
 		RCU_INIT_POINTER(tfile->tun, NULL);
@@ -774,7 +775,7 @@ static void tun_detach_all(struct net_device *dev)
 	synchronize_net();
 	for (i = 0; i < n; i++) {
 		tfile = rtnl_dereference(tun->tfiles[i]);
-		tun_napi_del(tun, tfile);
+		tun_napi_del(tfile);
 		/* Drop read queue */
 		tun_queue_purge(tfile);
 		xdp_rxq_info_unreg(&tfile->xdp_rxq);
@@ -793,7 +794,7 @@ static void tun_detach_all(struct net_device *dev)
 }
 
 static int tun_attach(struct tun_struct *tun, struct file *file,
-		      bool skip_filter, bool napi)
+		      bool skip_filter, bool napi, bool napi_frags)
 {
 	struct tun_file *tfile = file->private_data;
 	struct net_device *dev = tun->dev;
@@ -866,7 +867,7 @@ static int tun_attach(struct tun_struct *tun, struct file *file,
 		tun_enable_queue(tfile);
 	} else {
 		sock_hold(&tfile->sk);
-		tun_napi_init(tun, tfile, napi);
+		tun_napi_init(tun, tfile, napi, napi_frags);
 	}
 
 	tun_set_real_num_queues(tun);
@@ -1709,7 +1710,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 	int err;
 	u32 rxhash = 0;
 	int skb_xdp = 1;
-	bool frags = tun_napi_frags_enabled(tun);
+	bool frags = tun_napi_frags_enabled(tfile);
 
 	if (!(tun->dev->flags & IFF_UP))
 		return -EIO;
@@ -2534,7 +2535,8 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 			return err;
 
 		err = tun_attach(tun, file, ifr->ifr_flags & IFF_NOFILTER,
-				 ifr->ifr_flags & IFF_NAPI);
+				 ifr->ifr_flags & IFF_NAPI,
+				 ifr->ifr_flags & IFF_NAPI_FRAGS);
 		if (err < 0)
 			return err;
 
@@ -2632,7 +2634,8 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 			      (ifr->ifr_flags & TUN_FEATURES);
 
 		INIT_LIST_HEAD(&tun->disabled);
-		err = tun_attach(tun, file, false, ifr->ifr_flags & IFF_NAPI);
+		err = tun_attach(tun, file, false, ifr->ifr_flags & IFF_NAPI,
+				 ifr->ifr_flags & IFF_NAPI_FRAGS);
 		if (err < 0)
 			goto err_free_flow;
 
@@ -2781,7 +2784,8 @@ static int tun_set_queue(struct file *file, struct ifreq *ifr)
 		ret = security_tun_dev_attach_queue(tun->security);
 		if (ret < 0)
 			goto unlock;
-		ret = tun_attach(tun, file, false, tun->flags & IFF_NAPI);
+		ret = tun_attach(tun, file, false, tun->flags & IFF_NAPI,
+				 tun->flags & IFF_NAPI_FRAGS);
 	} else if (ifr->ifr_flags & IFF_DETACH_QUEUE) {
 		tun = rtnl_dereference(tfile->tun);
 		if (!tun || !(tun->flags & IFF_MULTI_QUEUE) || tfile->detached)
@@ -3199,6 +3203,7 @@ static int tun_chr_open(struct inode *inode, struct file * file)
 		return -ENOMEM;
 	}
 
+	mutex_init(&tfile->napi_mutex);
 	RCU_INIT_POINTER(tfile->tun, NULL);
 	tfile->flags = 0;
 	tfile->ifindex = 0;