[PATCH net-next 11/11] can: protect the receive lists with a per-device lock

[Marc Kleine-Budde <mkl@pengutronix.de>]

From: Oliver Hartkopp <socketcan@hartkopp.net>

The receive lists of a CAN device are located in the device's
can_ml_priv and travel with the device when it is moved to another
network namespace. But they are protected by the per-netns
rcvlists_lock. So can_rx_unregister() needs dev_net(dev) to pick the
right lock and silently returns when the passed namespace does not
match dev_net(dev) anymore.

isotp_release() and bcm_release() leave their notifier list before they
take any lock that serializes against the netdev notifier, which runs
under RTNL. When the bound device is moved to another namespace in this
window, the notifier skips the socket and the release path has to remove
the filters itself. isotp_release() passes the socket's namespace, which
does not match dev_net(dev) anymore. bcm_rx_unreg() passes dev_net(dev),
which can_rx_unregister() reads again for its check, so a namespace
change between both reads makes the check fail as well. In both cases
can_rx_unregister() silently returns. As can_rx_register() stores
rcv->sk without a reference, the remaining receivers point to the freed
socket (isotp) or the freed op (bcm):

  BUG: KASAN: use-after-free in isotp_rcv+0x1570/0x24d0
  Read of size 1 at addr ffff888118130552 by task isotp_ns_uaf/578
   can_rcv_filter+0x4af/0x8c0
   can_receive+0x28d/0x3c0
   can_rcv+0x2a9/0x310
   __netif_receive_skb_one_core+0x21a/0x260
   process_backlog+0x210/0x760

Besides this, the lists of a device are protected by the rcvlists_lock
of the namespace that is passed in. Callers which pass dev_net(dev) read
it at different times, so the same lists may be modified under the locks
of different namespaces while the device is moved.

Taking RTNL in these release paths is no option: raw_bind(),
raw_setsockopt() and raw_release() already hold RTNL while adding and
removing up to CAN_RAW_FILTER_MAX filters per socket, which unprivileged
users can trigger repeatedly and which makes RTNL a global bottleneck.

Instead fix the root cause and add a spinlock to struct
can_dev_rcv_lists, which protects the receive lists of a CAN device or
the 'any' CAN device lists of a namespace. It is initialized in
can_set_ml_priv(), which is used by all CAN network devices. With this,
can_rx_unregister() finds the subscription independently of the
current namespace of the device. The protocols keep the device valid
with their tracked references. The per-netns rcvlists_lock only protects
the receive list statistics anymore, and CAN_RAW, CAN_BCM and CAN_ISOTP
pass the namespace that has been used for can_rx_register().

So isotp_release() and bcm_release() now remove their filters correctly
without RTNL, and raw_release(), raw_setsockopt(), raw_bind() and
isotp_bind() do not need RTNL anymore and add and remove their filters
under lock_sock(). To serialize bind() with NETDEV_UNREGISTER, bind()
publishes the device inside the RCU section of its lookup, and
raw_notify() and isotp_notify() recheck the bound device under lock_sock().
As RTNL does not keep NETDEV_DOWN out of bind() anymore, bind() checks
IFF_UP after publishing the bound device, with a barrier pair against
raw_notify() and isotp_notify(), so a down transition during bind() is
still reported with ENETDOWN.

Fixes: 20bab8b88baa ("can: isotp: fix use-after-free race with concurrent NETDEV_UNREGISTER")
Fixes: 8e8cda6d737d ("can: initial support for network namespaces")
Reported-by: Norbert Szetei <norbert@doyensec.com>
Link: https://lore.kernel.org/linux-can/CEA6A38A-2646-4ADA-95B4-CBAE2F301A8E@doyensec.com/
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20261021215456.119268-1-socketcan@hartkopp.net
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 include/linux/can/can-ml.h |   3 +
 include/net/netns/can.h    |   2 +-
 net/can/af_can.c           |  41 ++++++----
 net/can/bcm.c              |  43 +++-------
 net/can/isotp.c            |  58 ++++++++------
 net/can/raw.c              | 155 ++++++++++++++++++++++++-------------
 6 files changed, 181 insertions(+), 121 deletions(-)

diff --git a/include/linux/can/can-ml.h b/include/linux/can/can-ml.h
index 1e99fda2b380..cfefa4a385be 100644
--- a/include/linux/can/can-ml.h
+++ b/include/linux/can/can-ml.h
@@ -45,6 +45,7 @@
 #include <linux/can.h>
 #include <linux/list.h>
 #include <linux/netdevice.h>
+#include <linux/spinlock.h>
 
 /* exposed CAN device capabilities for network layer */
 #define CAN_CAP_CC BIT(0) /* CAN CC aka Classical CAN */
@@ -59,6 +60,7 @@
 enum { RX_ERR, RX_ALL, RX_FIL, RX_INV, RX_MAX };
 
 struct can_dev_rcv_lists {
+	spinlock_t lock; /* protects the receive lists and entries */
 	struct hlist_head rx[RX_MAX];
 	struct hlist_head rx_sff[CAN_SFF_RCV_ARRAY_SZ];
 	struct hlist_head rx_eff[CAN_EFF_RCV_ARRAY_SZ];
@@ -81,6 +83,7 @@ static inline struct can_ml_priv *can_get_ml_priv(struct net_device *dev)
 static inline void can_set_ml_priv(struct net_device *dev,
 				   struct can_ml_priv *ml_priv)
 {
+	spin_lock_init(&ml_priv->dev_rcv_lists.lock);
 	netdev_set_ml_priv(dev, ml_priv, ML_PRIV_CAN);
 }
 
diff --git a/include/net/netns/can.h b/include/net/netns/can.h
index 48b79f7e6236..54f23681e0d4 100644
--- a/include/net/netns/can.h
+++ b/include/net/netns/can.h
@@ -29,7 +29,7 @@ struct netns_can {
 
 	/* receive filters subscribed for 'all' CAN devices */
 	struct can_dev_rcv_lists *rx_alldev_list;
-	spinlock_t rcvlists_lock;
+	spinlock_t rcvlists_lock; /* protects the rcv_entries(_max) stats */
 	struct timer_list stattimer; /* timer for statistics update */
 	struct can_pkg_stats *pkg_stats;
 	struct can_rcv_lists_stats *rcv_lists_stats;
diff --git a/net/can/af_can.c b/net/can/af_can.c
index d97f85fc3232..0f3051a61aab 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -462,9 +462,10 @@ int can_rx_register(struct net *net, struct net_device *dev, canid_t can_id,
 	if (!rcv)
 		return -ENOMEM;
 
-	spin_lock_bh(&net->can.rcvlists_lock);
-
 	dev_rcv_lists = can_dev_rcv_lists_find(net, dev);
+
+	spin_lock_bh(&dev_rcv_lists->lock);
+
 	rcv_list = can_rcv_list_find(&can_id, &mask, dev_rcv_lists);
 
 	rcv->can_id = can_id;
@@ -478,6 +479,9 @@ int can_rx_register(struct net *net, struct net_device *dev, canid_t can_id,
 	hlist_add_head_rcu(&rcv->list, rcv_list);
 	dev_rcv_lists->entries++;
 
+	spin_unlock_bh(&dev_rcv_lists->lock);
+
+	spin_lock_bh(&net->can.rcvlists_lock);
 	rcv_lists_stats->rcv_entries++;
 	rcv_lists_stats->rcv_entries_max = max(rcv_lists_stats->rcv_entries_max,
 					       rcv_lists_stats->rcv_entries);
@@ -509,6 +513,14 @@ static void can_rx_delete_receiver(struct rcu_head *rp)
  *
  * Description:
  *  Removes subscription entry depending on given (subscription) values.
+ *  The receive lists of a CAN device are protected by a per-device lock,
+ *  so the subscription is found even when the device has been moved to
+ *  another network namespace after can_rx_register(). The caller has to
+ *  ensure that @dev stays valid, e.g. by holding a reference to @dev or
+ *  RTNL. @net should be the namespace that has been used for
+ *  can_rx_register(). It selects the 'any' CAN device lists for
+ *  @dev == NULL and is otherwise only used for the receive list
+ *  statistics, which become imprecise when another namespace is passed.
  */
 void can_rx_unregister(struct net *net, struct net_device *dev, canid_t can_id,
 		       canid_t mask, void (*func)(struct sk_buff *, void *),
@@ -522,12 +534,10 @@ void can_rx_unregister(struct net *net, struct net_device *dev, canid_t can_id,
 	if (dev && !can_get_ml_priv(dev))
 		return;
 
-	if (dev && !net_eq(net, dev_net(dev)))
-		return;
-
-	spin_lock_bh(&net->can.rcvlists_lock);
-
 	dev_rcv_lists = can_dev_rcv_lists_find(net, dev);
+
+	spin_lock_bh(&dev_rcv_lists->lock);
+
 	rcv_list = can_rcv_list_find(&can_id, &mask, dev_rcv_lists);
 
 	/* Search the receiver list for the item to delete.  This should
@@ -547,26 +557,26 @@ void can_rx_unregister(struct net *net, struct net_device *dev, canid_t can_id,
 	 * a warning here.
 	 */
 	if (!rcv) {
+		spin_unlock_bh(&dev_rcv_lists->lock);
 		pr_warn("can: receive list entry not found for dev %s, id %03X, mask %03X\n",
 			DNAME(dev), can_id, mask);
-		goto out;
+		return;
 	}
 
 	hlist_del_rcu(&rcv->list);
 	dev_rcv_lists->entries--;
 
+	spin_unlock_bh(&dev_rcv_lists->lock);
+
+	spin_lock_bh(&net->can.rcvlists_lock);
 	if (rcv_lists_stats->rcv_entries > 0)
 		rcv_lists_stats->rcv_entries--;
-
- out:
 	spin_unlock_bh(&net->can.rcvlists_lock);
 
 	/* schedule the receiver item for deletion */
-	if (rcv) {
-		if (rcv->sk)
-			sock_hold(rcv->sk);
-		call_rcu(&rcv->rcu, can_rx_delete_receiver);
-	}
+	if (rcv->sk)
+		sock_hold(rcv->sk);
+	call_rcu(&rcv->rcu, can_rx_delete_receiver);
 }
 EXPORT_SYMBOL(can_rx_unregister);
 
@@ -823,6 +833,7 @@ static int can_pernet_init(struct net *net)
 	net->can.rx_alldev_list = kzalloc_obj(*net->can.rx_alldev_list);
 	if (!net->can.rx_alldev_list)
 		goto out;
+	spin_lock_init(&net->can.rx_alldev_list->lock);
 	net->can.pkg_stats = kzalloc_obj(*net->can.pkg_stats);
 	if (!net->can.pkg_stats)
 		goto out_free_rx_alldev_list;
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 6759662e024c..7bd2aa39777a 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -962,7 +962,7 @@ static void bcm_remove_op(struct bcm_op *op)
 static void bcm_rx_unreg(struct net_device *dev, struct bcm_op *op)
 {
 	if (op->rx_reg_dev == dev) {
-		can_rx_unregister(dev_net(dev), dev, op->can_id,
+		can_rx_unregister(sock_net(op->sk), dev, op->can_id,
 				  REGMASK(op->can_id), bcm_rx_handler, op);
 
 		/* mark as removed subscription */
@@ -988,21 +988,10 @@ static int bcm_delete_rx_op(struct list_head *ops, struct bcm_msg_head *mh,
 			/* disable automatic timer on frame reception */
 			op->flags |= RX_NO_AUTOTIMER;
 
-			/*
-			 * Don't care if we're bound or not (due to netdev
-			 * problems) can_rx_unregister() is always a save
-			 * thing to do here.
-			 */
 			if (op->ifindex) {
-				/*
-				 * Only remove subscriptions that had not
-				 * been removed due to NETDEV_UNREGISTER
-				 * in bcm_notifier()
-				 *
-				 * op->rx_reg_dev is a tracked reference taken
-				 * when the subscription was registered, so it
-				 * stays valid here even if a concurrent
-				 * NETDEV_UNREGISTER already unlisted the dev.
+				/* Only remove subscriptions that had not been
+				 * removed in bcm_notify(). op->rx_reg_dev keeps
+				 * the device's receive lists accessible.
 				 */
 				if (op->rx_reg_dev)
 					bcm_rx_unreg(op->rx_reg_dev, op);
@@ -1935,6 +1924,7 @@ static int bcm_release(struct socket *sock)
 	list_del(&bo->notifier);
 	spin_unlock(&bcm_notifier_lock);
 
+	/* bcm_notify() can not access this socket anymore */
 	lock_sock(sk);
 
 #if IS_ENABLED(CONFIG_PROC_FS)
@@ -1948,29 +1938,20 @@ static int bcm_release(struct socket *sock)
 		bcm_remove_op(op);
 	}
 
-	list_for_each_entry_safe(op, next, &bo->rx_ops, list) {
-		/*
-		 * Don't care if we're bound or not (due to netdev problems)
-		 * can_rx_unregister() is always a save thing to do here.
-		 */
+	list_for_each_entry(op, &bo->rx_ops, list) {
 		if (op->ifindex) {
-			/*
-			 * Only remove subscriptions that had not
-			 * been removed due to NETDEV_UNREGISTER
-			 * in bcm_notifier()
-			 *
-			 * op->rx_reg_dev is a tracked reference taken
-			 * when the subscription was registered, so it
-			 * stays valid here even if a concurrent
-			 * NETDEV_UNREGISTER already unlisted the device.
+			/* Only remove subscriptions that had not been removed
+			 * in bcm_notify(). op->rx_reg_dev keeps the device's
+			 * receive lists accessible.
 			 */
 			if (op->rx_reg_dev)
 				bcm_rx_unreg(op->rx_reg_dev, op);
-		} else
+		} else {
 			can_rx_unregister(net, NULL, op->can_id,
 					  REGMASK(op->can_id),
 					  bcm_rx_handler, op);
-
+		}
+		cond_resched();
 	}
 
 	synchronize_rcu();
diff --git a/net/can/isotp.c b/net/can/isotp.c
index 5e1c3971ebfc..9386389cd702 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1497,11 +1497,11 @@ static int isotp_release(struct socket *sock)
 	list_del(&so->notifier);
 	spin_unlock(&isotp_notifier_lock);
 
-	rtnl_lock();
 	lock_sock(sk);
 
 	/* remove current filters & unregister
-	 * tracked reference so->dev is taken at bind() time with rtnl_lock
+	 * the tracked reference so->dev keeps the device's receive lists
+	 * accessible, even after a namespace change
 	 */
 	if (so->bound && so->dev) {
 		if (isotp_register_rxid(so))
@@ -1519,8 +1519,6 @@ static int isotp_release(struct socket *sock)
 	so->bound = 0;
 	so->dev = NULL;
 
-	rtnl_unlock();
-
 	/* Always wait for a grace period before touching the timers below.
 	 * A concurrent NETDEV_UNREGISTER may have already unregistered our
 	 * filters and cleared so->bound in isotp_notify() without waiting
@@ -1588,7 +1586,7 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
 	if (!addr->can_ifindex)
 		return -ENODEV;
 
-	rtnl_lock();
+	/* lock_sock() serializes the binding with isotp_notify() */
 	lock_sock(sk);
 
 	if (so->bound) {
@@ -1614,20 +1612,30 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
 		goto out;
 	}
 
-	dev = dev_get_by_index(net, addr->can_ifindex);
-	if (!dev) {
+	/* Publish the device inside the RCU section of the lookup: When it
+	 * is unlisted concurrently, either isotp_notify() sees so->dev after
+	 * synchronize_net() or the lookup fails. Check the device before, so
+	 * that bind() can not fail after so->dev has been published.
+	 */
+	rcu_read_lock();
+	dev = dev_get_by_index_rcu(net, addr->can_ifindex);
+	if (!dev || !can_get_ml_priv(dev))
 		err = -ENODEV;
-		goto out;
-	}
-	if (!can_get_ml_priv(dev)) {
-		err = -ENODEV;
-		goto out_put_dev;
-	}
-	if (READ_ONCE(dev->mtu) < so->ll.mtu) {
+	else if (READ_ONCE(dev->mtu) < so->ll.mtu)
 		err = -EINVAL;
-		goto out_put_dev;
+	if (!err) {
+		dev_hold(dev);
+		WRITE_ONCE(so->dev, dev);
 	}
-	if (!(dev->flags & IFF_UP))
+	rcu_read_unlock();
+	if (err)
+		goto out;
+
+	/* Either isotp_notify() sees so->dev on NETDEV_DOWN or we see the
+	 * cleared IFF_UP, pairs with isotp_notify()
+	 */
+	smp_mb();
+	if (!(READ_ONCE(dev->flags) & IFF_UP))
 		notify_enetdown = 1;
 
 	ifindex = dev->ifindex;
@@ -1653,15 +1661,12 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
 	 * can safely reach the device later, even if a concurrent
 	 * NETDEV_UNREGISTER has already unlisted it by ifindex.
 	 */
-	so->dev = dev;
 	netdev_hold(so->dev, &so->dev_tracker, GFP_KERNEL);
 
-out_put_dev:
-	/* remove potential reference from dev_get_by_index() */
+	/* remove reference from the device lookup */
 	dev_put(dev);
 out:
 	release_sock(sk);
-	rtnl_unlock();
 
 	if (notify_enetdown) {
 		sk->sk_err = ENETDOWN;
@@ -1864,12 +1869,21 @@ static void isotp_notify(struct isotp_sock *so, unsigned long msg,
 	if (!net_eq(dev_net(dev), sock_net(sk)))
 		return;
 
-	if (so->dev != dev)
+	if (msg == NETDEV_DOWN)
+		smp_mb(); /* pairs with isotp_bind(), see raw_notify() */
+
+	/* lockless fast path, see raw_notify() */
+	if (READ_ONCE(so->dev) != dev)
 		return;
 
 	switch (msg) {
 	case NETDEV_UNREGISTER:
 		lock_sock(sk);
+		if (so->dev != dev) {
+			release_sock(sk);
+			break;
+		}
+
 		/* remove current filters & unregister */
 		if (so->bound) {
 			if (isotp_register_rxid(so))
@@ -1885,7 +1899,7 @@ static void isotp_notify(struct isotp_sock *so, unsigned long msg,
 
 		so->ifindex = 0;
 		so->bound  = 0;
-		so->dev = NULL;
+		WRITE_ONCE(so->dev, NULL);
 		release_sock(sk);
 
 		sk->sk_err = ENODEV;
diff --git a/net/can/raw.c b/net/can/raw.c
index dfea48768b23..d07f3bb68cd5 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -85,6 +85,7 @@ struct raw_sock {
 	struct sock sk;
 	struct net_device *dev;
 	netdevice_tracker dev_tracker;
+	struct net_device *bind_dev; /* hint for raw_notify(), no reference */
 	struct list_head notifier;
 	int ifindex;
 	unsigned int bound:1;
@@ -224,6 +225,7 @@ static int raw_enable_filters(struct net *net, struct net_device *dev,
 	int i;
 
 	for (i = 0; i < count; i++) {
+		cond_resched();
 		err = can_rx_register(net, dev, filter[i].can_id,
 				      filter[i].can_mask,
 				      raw_rcv, sk, sock_i_ino(sk), sk);
@@ -258,9 +260,11 @@ static void raw_disable_filters(struct net *net, struct net_device *dev,
 {
 	int i;
 
-	for (i = 0; i < count; i++)
+	for (i = 0; i < count; i++) {
 		can_rx_unregister(net, dev, filter[i].can_id,
 				  filter[i].can_mask, raw_rcv, sk);
+		cond_resched();
+	}
 }
 
 static inline void raw_disable_errfilter(struct net *net,
@@ -305,16 +309,31 @@ static void raw_notify(struct raw_sock *ro, unsigned long msg,
 		       struct net_device *dev)
 {
 	struct sock *sk = &ro->sk;
+	struct net_device *bind_dev;
 
 	if (!net_eq(dev_net(dev), sock_net(sk)))
 		return;
 
-	if (ro->dev != dev)
+	if (msg == NETDEV_DOWN)
+		smp_mb(); /* IFF_UP is cleared before, pairs with raw_bind() */
+
+	/* Lockless fast path, ro->bind_dev covers a concurrent bind().
+	 * Read it before ro->dev, pairs with smp_store_release() in
+	 * raw_bind(). A stale ro->bind_dev only costs a lock_sock().
+	 */
+	bind_dev = smp_load_acquire(&ro->bind_dev);
+	if (READ_ONCE(ro->dev) != dev &&
+	    (msg != NETDEV_UNREGISTER || bind_dev != dev))
 		return;
 
 	switch (msg) {
 	case NETDEV_UNREGISTER:
 		lock_sock(sk);
+		if (ro->dev != dev) {
+			release_sock(sk);
+			break;
+		}
+
 		/* remove current filters & unregister */
 		if (ro->bound) {
 			raw_disable_allfilters(dev_net(dev), dev, sk);
@@ -326,7 +345,7 @@ static void raw_notify(struct raw_sock *ro, unsigned long msg,
 
 		ro->ifindex = 0;
 		ro->bound = 0;
-		ro->dev = NULL;
+		WRITE_ONCE(ro->dev, NULL);
 		ro->count = 0;
 		release_sock(sk);
 
@@ -381,6 +400,7 @@ static int raw_init(struct sock *sk)
 	ro->bound            = 0;
 	ro->ifindex          = 0;
 	ro->dev              = NULL;
+	ro->bind_dev         = NULL;
 
 	/* set default filter to single entry dfilter */
 	ro->dfilter.can_id   = 0;
@@ -431,13 +451,15 @@ static int raw_release(struct socket *sock)
 	list_del(&ro->notifier);
 	spin_unlock(&raw_notifier_lock);
 
-	rtnl_lock();
 	lock_sock(sk);
 
-	/* remove current filters & unregister */
+	/* remove current filters & unregister
+	 * the tracked reference ro->dev keeps the device's receive lists
+	 * accessible, even after a namespace change
+	 */
 	if (ro->bound) {
 		if (ro->dev) {
-			raw_disable_allfilters(dev_net(ro->dev), ro->dev, sk);
+			raw_disable_allfilters(net, ro->dev, sk);
 			netdev_put(ro->dev, &ro->dev_tracker);
 		} else {
 			raw_disable_allfilters(net, NULL, sk);
@@ -456,7 +478,6 @@ static int raw_release(struct socket *sock)
 	sock->sk = NULL;
 
 	release_sock(sk);
-	rtnl_unlock();
 
 	sock_prot_inuse_add(net, sk->sk_prot, -1);
 	sock_put(sk);
@@ -479,14 +500,25 @@ static int raw_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int len
 	if (addr->can_family != AF_CAN)
 		return -EINVAL;
 
-	rtnl_lock();
+	/* lock_sock() serializes the binding with raw_notify() */
 	lock_sock(sk);
 
 	if (ro->bound && addr->can_ifindex == ro->ifindex)
 		goto out;
 
 	if (addr->can_ifindex) {
-		dev = dev_get_by_index(sock_net(sk), addr->can_ifindex);
+		/* Publish the device inside the RCU section of the lookup:
+		 * When it is unlisted concurrently, either raw_notify() sees
+		 * ro->bind_dev after synchronize_net() or the lookup fails.
+		 */
+		rcu_read_lock();
+		dev = dev_get_by_index_rcu(sock_net(sk), addr->can_ifindex);
+		if (dev) {
+			dev_hold(dev);
+			/* pairs with smp_load_acquire() in raw_notify() */
+			smp_store_release(&ro->bind_dev, dev);
+		}
+		rcu_read_unlock();
 		if (!dev) {
 			err = -ENODEV;
 			goto out;
@@ -496,9 +528,6 @@ static int raw_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int len
 			goto out_put_dev;
 		}
 
-		if (!(dev->flags & IFF_UP))
-			notify_enetdown = 1;
-
 		ifindex = dev->ifindex;
 
 		/* filters set by default/setsockopt */
@@ -517,7 +546,7 @@ static int raw_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int len
 		if (ro->bound) {
 			/* unregister old filters */
 			if (ro->dev) {
-				raw_disable_allfilters(dev_net(ro->dev),
+				raw_disable_allfilters(sock_net(sk),
 						       ro->dev, sk);
 				/* drop reference to old ro->dev */
 				netdev_put(ro->dev, &ro->dev_tracker);
@@ -528,16 +557,24 @@ static int raw_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int len
 		ro->ifindex = ifindex;
 		ro->bound = 1;
 		/* bind() ok -> hold a reference for new ro->dev */
-		ro->dev = dev;
+		WRITE_ONCE(ro->dev, dev);
 		netdev_hold(ro->dev, &ro->dev_tracker, GFP_KERNEL);
+
+		if (dev) {
+			/* Either raw_notify() sees ro->dev on NETDEV_DOWN or
+			 * we see the cleared IFF_UP, pairs with raw_notify()
+			 */
+			smp_mb();
+			if (!(READ_ONCE(dev->flags) & IFF_UP))
+				notify_enetdown = 1;
+		}
 	}
 
 out_put_dev:
-	/* remove potential reference from dev_get_by_index() */
+	/* remove reference from the device lookup */
 	dev_put(dev);
 out:
 	release_sock(sk);
-	rtnl_unlock();
 
 	if (notify_enetdown) {
 		sk->sk_err = ENETDOWN;
@@ -566,58 +603,41 @@ static int raw_getname(struct socket *sock, struct sockaddr *uaddr,
 }
 
 static int raw_setsockopt_locked(struct socket *sock, int optname,
-				 sockptr_t optval, unsigned int optlen)
+				 sockptr_t optval, unsigned int optlen,
+				 struct can_filter *filter,
+				 struct can_filter *sfilter, int count)
 {
 	struct sock *sk = sock->sk;
 	struct raw_sock *ro = raw_sk(sk);
-	struct can_filter *filter = NULL;  /* dyn. alloc'ed filters */
-	struct can_filter sfilter;         /* single filter */
 	struct net_device *dev = NULL;
 	can_err_mask_t err_mask = 0;
-	int count = 0;
 	int flag;
 	int err = 0;
 
 	switch (optname) {
 	case CAN_RAW_FILTER:
-		if (optlen % sizeof(struct can_filter) != 0)
-			return -EINVAL;
-
-		if (optlen > CAN_RAW_FILTER_MAX * sizeof(struct can_filter))
-			return -EINVAL;
-
-		count = optlen / sizeof(struct can_filter);
-
-		if (count > 1) {
-			/* filter does not fit into dfilter => alloc space */
-			filter = memdup_sockptr(optval, optlen);
-			if (IS_ERR(filter))
-				return PTR_ERR(filter);
-		} else if (count == 1) {
-			if (copy_from_sockptr(&sfilter, optval, sizeof(sfilter)))
-				return -EFAULT;
-		}
-
+		/* @filter has been copied by raw_setsockopt(). It is linked
+		 * to the socket on success and freed by the caller on error.
+		 *
+		 * The reg_state check is only a shortcut: On a concurrent
+		 * unregistration or namespace change raw_notify() waits for
+		 * lock_sock() and removes the filters set here.
+		 */
 		dev = ro->dev;
-		if (ro->bound && dev && dev->reg_state != NETREG_REGISTERED) {
-			if (count > 1)
-				kfree(filter);
+		if (ro->bound && dev &&
+		    READ_ONCE(dev->reg_state) != NETREG_REGISTERED)
 			return -ENODEV;
-		}
 
 		if (ro->bound) {
 			/* (try to) register the new filters */
 			if (count == 1)
 				err = raw_enable_filters(sock_net(sk), dev, sk,
-							 &sfilter, 1);
+							 sfilter, 1);
 			else
 				err = raw_enable_filters(sock_net(sk), dev, sk,
 							 filter, count);
-			if (err) {
-				if (count > 1)
-					kfree(filter);
+			if (err)
 				return err;
-			}
 
 			/* remove old filter registrations */
 			raw_disable_filters(sock_net(sk), dev, sk, ro->filter,
@@ -631,7 +651,7 @@ static int raw_setsockopt_locked(struct socket *sock, int optname,
 		/* link new filters to the socket */
 		if (count == 1) {
 			/* copy filter data for single filter */
-			ro->dfilter = sfilter;
+			ro->dfilter = *sfilter;
 			filter = &ro->dfilter;
 		}
 		ro->filter = filter;
@@ -647,8 +667,10 @@ static int raw_setsockopt_locked(struct socket *sock, int optname,
 
 		err_mask &= CAN_ERR_MASK;
 
+		/* lockless shortcut, see CAN_RAW_FILTER */
 		dev = ro->dev;
-		if (ro->bound && dev && dev->reg_state != NETREG_REGISTERED)
+		if (ro->bound && dev &&
+		    READ_ONCE(dev->reg_state) != NETREG_REGISTERED)
 			return -ENODEV;
 
 		/* remove current error mask */
@@ -750,18 +772,47 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,
 			  sockptr_t optval, unsigned int optlen)
 {
 	struct sock *sk = sock->sk;
+	struct can_filter *filter = NULL;  /* dyn. alloc'ed filters */
+	struct can_filter sfilter;         /* single filter */
+	int count = 0;
 	int err;
 
 	if (level != SOL_CAN_RAW)
 		return -EINVAL;
 
-	rtnl_lock();
+	if (optname == CAN_RAW_FILTER) {
+		/* Copy the filters before lock_sock(), so a stalled copy can
+		 * not block raw_notify() waiting for lock_sock() under RTNL.
+		 */
+		if (optlen % sizeof(struct can_filter) != 0)
+			return -EINVAL;
+
+		if (optlen > CAN_RAW_FILTER_MAX * sizeof(struct can_filter))
+			return -EINVAL;
+
+		count = optlen / sizeof(struct can_filter);
+
+		if (count > 1) {
+			/* filter does not fit into dfilter => alloc space */
+			filter = memdup_sockptr(optval, optlen);
+			if (IS_ERR(filter))
+				return PTR_ERR(filter);
+		} else if (count == 1) {
+			if (copy_from_sockptr(&sfilter, optval, sizeof(sfilter)))
+				return -EFAULT;
+		}
+	}
+
 	lock_sock(sk);
 
-	err = raw_setsockopt_locked(sock, optname, optval, optlen);
+	err = raw_setsockopt_locked(sock, optname, optval, optlen,
+				    filter, &sfilter, count);
 
 	release_sock(sk);
-	rtnl_unlock();
+
+	/* on error free the filters allocated for CAN_RAW_FILTER above */
+	if (err && count > 1)
+		kfree(filter);
 
 	return err;
 }
-- 
2.53.0