[PATCH net-next 05/11] can: isotp: check the frame type, not just the length

[PATCH net-next 05/11] can: isotp: check the frame type, not just the length

[Marc Kleine-Budde]

From: Kaixuan Li <kaixuanli0131@gmail.com>

isotp_rcv() separates Classic CAN from CAN FD by skb->len alone:

	if (skb->len != so->ll.mtu)
		return;

	cf = (struct canfd_frame *)skb->data;

A CAN XL frame with cxl->len 4 is CAN_MTU bytes, so it passes, and is then
read as a canfd_frame whose len comes out of canxl_frame.flags: at least
0x80.

Of the paths that follow, only the flow control one uses that length
without bounding it first, so check_pad() walks to 255 over a 16-byte
frame and the caller reports EBADMSG on an unrelated socket.

bcm_rx_handler(), j1939_can_recv(), can_can_gw_rcv() and raw_rcv() check
the frame type here, and can_dropped_invalid_skb() switches on
skb->protocol on the transmit side. isotp_rcv() is the gap.

Fixes: fb08cba12b52 ("can: canxl: update CAN infrastructure for CAN XL frames")
Signed-off-by: Kaixuan Li <kaixuanli0131@gmail.com>
Reviewed-by: Oliver Hartkopp <socketcan@hartkopp.net>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Reviewed-by: Quchaosheng <quchaosheng000406@163.com>
Link: https://patch.msgid.link/20260920035626.2581040-1-kaixuanli0131@gmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 net/can/isotp.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/can/isotp.c b/net/can/isotp.c
index f5dc9d04bd68..d3e43ab48425 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -755,6 +755,14 @@ static void isotp_rcv(struct sk_buff *skb, void *data)
 	if (skb->len != so->ll.mtu)
 		return;
 
+	/* check for correct CAN CC/FD frame content */
+	if (so->ll.mtu == CAN_MTU) {
+		if (!can_is_can_skb(skb))
+			return;
+	} else if (!can_is_canfd_skb(skb)) {
+		return;
+	}
+
 	cf = (struct canfd_frame *)skb->data;
 
 	/* if enabled: check reception of my configured extended address */
-- 
2.53.0

[PATCH net-next 06/11] can: proc: reset pkg_stats atomics individually

[Marc Kleine-Budde]

From: Runyu Xiao <runyu.xiao@seu.edu.cn>

Commit 80b5f90158d1 ("can: statistics: use atomic access in hot path")
converted several members of struct can_pkg_stats to atomic_long_t and
updated the hot TX/RX and procfs read paths to use atomic_long_*()
helpers. However, can_init_stats() still clears the whole struct with
memset().

can_init_stats() is reached from can_stat_update() in timer context and
also from the procfs reset path. Those paths can run while the TX/RX hot
paths are concurrently updating rx_frames, tx_frames, matches and their
*_delta counters. Hitting the whole-struct memset() in that window
performs plain writes to fields that otherwise follow an atomic_long_t
access contract, which can lose or mix live statistics updates.

This issue was found by source-level API-misuse analysis looking for
whole-object resets left behind after atomic_long_t conversions, then
manually audited on Linux v6.18.21.

Replace the whole-struct memset() with a helper that resets the
atomic_long_t counters via atomic_long_set() and clears the derived
scalar statistics explicitly. This preserves the existing reset
semantics for scalar fields while restoring atomic access discipline for
the live counters.

Build-tested by compiling net/can/proc.o on x86_64 netdev/main.
Runtime-tested with a QEMU + vcan setup on Linux v6.18.21 by driving
concurrent traffic and reset_stats reads, which reproduced inconsistent
exported statistics before the fix.

[Hartkopp] can_stat_update() also read the *_delta counters at the
beginning and cleared them with atomic_long_set() at the end. Increments
from the hot path in between were lost for both the current and the next
interval. Use atomic_long_xchg() to fetch and clear the *_delta counters
in one atomic step instead.

Fixes: 80b5f90158d1 ("can: statistics: use atomic access in hot path")
Cc: stable@vger.kernel.org
Signed-off-by: Runyu Xiao <runyu.xiao@seu.edu.cn>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20261020203257.230955-2-socketcan@hartkopp.net
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 net/can/proc.c | 39 +++++++++++++++++++++++++++++----------
 1 file changed, 29 insertions(+), 10 deletions(-)

diff --git a/net/can/proc.c b/net/can/proc.c
index de4d05ae3459..70104f13077e 100644
--- a/net/can/proc.c
+++ b/net/can/proc.c
@@ -76,16 +76,39 @@ static const char rx_list_name[][8] = {
  * af_can statistics stuff
  */
 
+static void can_reset_pkg_stats(struct can_pkg_stats *pkg_stats)
+{
+	atomic_long_set(&pkg_stats->rx_frames, 0);
+	atomic_long_set(&pkg_stats->tx_frames, 0);
+	atomic_long_set(&pkg_stats->matches, 0);
+
+	pkg_stats->total_rx_rate = 0;
+	pkg_stats->total_tx_rate = 0;
+	pkg_stats->total_rx_match_ratio = 0;
+
+	pkg_stats->current_rx_rate = 0;
+	pkg_stats->current_tx_rate = 0;
+	pkg_stats->current_rx_match_ratio = 0;
+
+	pkg_stats->max_rx_rate = 0;
+	pkg_stats->max_tx_rate = 0;
+	pkg_stats->max_rx_match_ratio = 0;
+
+	atomic_long_set(&pkg_stats->rx_frames_delta, 0);
+	atomic_long_set(&pkg_stats->tx_frames_delta, 0);
+	atomic_long_set(&pkg_stats->matches_delta, 0);
+}
+
 static void can_init_stats(struct net *net)
 {
 	struct can_pkg_stats *pkg_stats = net->can.pkg_stats;
 	struct can_rcv_lists_stats *rcv_lists_stats = net->can.rcv_lists_stats;
 	/*
-	 * This memset function is called from a timer context (when
+	 * This stats reset is called from a timer context (when
 	 * can_stattimer is active which is the default) OR in a process
 	 * context (reading the proc_fs when can_stattimer is disabled).
 	 */
-	memset(pkg_stats, 0, sizeof(struct can_pkg_stats));
+	can_reset_pkg_stats(pkg_stats);
 	pkg_stats->jiffies_init = jiffies;
 
 	rcv_lists_stats->stats_reset++;
@@ -121,9 +144,10 @@ void can_stat_update(struct timer_list *t)
 	long rx_frames = atomic_long_read(&pkg_stats->rx_frames);
 	long tx_frames = atomic_long_read(&pkg_stats->tx_frames);
 	long matches = atomic_long_read(&pkg_stats->matches);
-	long rx_frames_delta = atomic_long_read(&pkg_stats->rx_frames_delta);
-	long tx_frames_delta = atomic_long_read(&pkg_stats->tx_frames_delta);
-	long matches_delta = atomic_long_read(&pkg_stats->matches_delta);
+	/* fetch and clear values for 'current rate' calculation */
+	long rx_frames_delta = atomic_long_xchg(&pkg_stats->rx_frames_delta, 0);
+	long tx_frames_delta = atomic_long_xchg(&pkg_stats->tx_frames_delta, 0);
+	long matches_delta = atomic_long_xchg(&pkg_stats->matches_delta, 0);
 
 	/* restart counting in timer context on user request */
 	if (user_reset)
@@ -172,11 +196,6 @@ void can_stat_update(struct timer_list *t)
 	if (pkg_stats->max_rx_match_ratio < pkg_stats->current_rx_match_ratio)
 		pkg_stats->max_rx_match_ratio = pkg_stats->current_rx_match_ratio;
 
-	/* clear values for 'current rate' calculation */
-	atomic_long_set(&pkg_stats->tx_frames_delta, 0);
-	atomic_long_set(&pkg_stats->rx_frames_delta, 0);
-	atomic_long_set(&pkg_stats->matches_delta, 0);
-
 	/* restart timer (one second) */
 	mod_timer(&net->can.stattimer, round_jiffies(jiffies + HZ));
 }
-- 
2.53.0

[PATCH net-next 10/11] can: dev: can_put_echo_skb(): free skb on invalid echo index

[Marc Kleine-Budde]

From: Cunhao Lu <1579567540@qq.com>

can_put_echo_skb() consumes the skb on all paths except when the echo
index is out of bounds. This leaves ownership with the caller on -EINVAL,
unlike the other error paths, and can leak the skb if the caller expects
consistent semantics.

Free the skb before returning -EINVAL so that all return paths consume it.

Fixes: 6411959c10fe ("can: dev: can_put_echo_skb(): don't crash kernel if can_priv::echo_skb is accessed out of bounds")
Cc: stable@vger.kernel.org
Reviewed-by: Vincent Mailhol <mailhol@kernel.org>
Signed-off-by: Cunhao Lu <1579567540@qq.com>
Link: https://patch.msgid.link/tencent_683AA16E643DE00211CD2FB62991264DC605@qq.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

---

FAQ:

Q: `can_skb_init_valid()` directly modifies `skb->data` without checking if
   the SKB is cloned or shared. Is this violating SKB shared buffer rules and
   causing data corruption?

A: The finding about can_skb_init_valid() modifying skb->data on a
   potentially shared buffer is not relevant for this (correct) patch.

   The FDF-flag write in can_skb_init_valid() only matters for PF_PACKET
   use: PF_CAN allocators already set CANFD_FDF. The write exists to
   normalize frames for PF_PACKET observers (tcpdump/Wireshark) so they can
   distinguish classic CAN from CAN FD at the netdev level, and to
   compensate for PF_PACKET senders that omit the bit. That normalization
   is functionally required.

   The shared-buffer concern only becomes realistic through a specific
   chain: a PF_PACKET sender injects a CANFD-sized frame, the CAN driver's
   loopback puts an echo skb back into can_rcv(), and cgw (without
   modfuncs) clones it for forwarding to another interface. Only on that
   second can_skb_init_valid() call is the skb cloned. By then the bit was
   already set on the exclusive skb during the initial xmit path, so the
   flags |= CANFD_FDF write is strictly idempotent for any parallel
   consumer of the shared buffer - no memory-safety or
   information-disclosure consequence. It's a formal violation of the skb
   sharing rules without an observable effect, so the current code can stay
   as-is.

Link: https://lore.kernel.org/all/54a3cc01-abcf-4a33-b932-39bb1f68cdd5@hartkopp.net/
[mkl: convert Oliver's mail to FAQ section]
---
 drivers/net/can/dev/skb.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index 3e36c0368bae..738d5968dfa6 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -55,6 +55,7 @@ int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
 	if (idx >= priv->echo_skb_max) {
 		netdev_err(dev, "%s: BUG! Trying to access can_priv::echo_skb out of bounds (%u/max %u)\n",
 			   __func__, idx, priv->echo_skb_max);
+		dev_kfree_skb_any(skb);
 		return -EINVAL;
 	}
 
-- 
2.53.0

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

[Marc Kleine-Budde]

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/20261020203257.230955-6-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            |  48 +++++++++---
 net/can/raw.c              | 155 ++++++++++++++++++++++++-------------
 6 files changed, 181 insertions(+), 111 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..8ec37d252557 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) {
@@ -1614,7 +1612,17 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
 		goto out;
 	}
 
-	dev = dev_get_by_index(net, addr->can_ifindex);
+	/* 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.
+	 */
+	rcu_read_lock();
+	dev = dev_get_by_index_rcu(net, addr->can_ifindex);
+	if (dev) {
+		dev_hold(dev);
+		WRITE_ONCE(so->dev, dev);
+	}
+	rcu_read_unlock();
 	if (!dev) {
 		err = -ENODEV;
 		goto out;
@@ -1627,7 +1635,12 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
 		err = -EINVAL;
 		goto out_put_dev;
 	}
-	if (!(dev->flags & IFF_UP))
+
+	/* 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 +1666,17 @@ 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() */
+	/* the published so->dev is only valid for a successful bind() */
+	if (err)
+		WRITE_ONCE(so->dev, NULL);
+
+	/* remove reference from the device lookup */
 	dev_put(dev);
 out:
 	release_sock(sk);
-	rtnl_unlock();
 
 	if (notify_enetdown) {
 		sk->sk_err = ENETDOWN;
@@ -1864,12 +1879,21 @@ 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 +1909,7 @@ 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

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

[Jakub Kicinski]

This is an AI-generated review of your patch. The human sending this
email has considered the AI review valid, or at least plausible.
---
can: protect the receive lists with a per-device lock

This commit adds a spinlock to struct can_dev_rcv_lists. The receive lists
of a CAN device are now protected per device instead of by the per-netns
rcvlists_lock, so can_rx_unregister() can find subscriptions after the
device has moved to another namespace.

RTNL is dropped from raw_bind(), raw_setsockopt(), raw_release(),
isotp_bind() and isotp_release(). These paths now use lock_sock() and a
device pointer published under RCU to serialize against the netdev
notifier.

Link: https://lore.kernel.org/linux-can/CEA6A38A-2646-4ADA-95B4-CBAE2F301A8E@doyensec.com/
Link: https://patch.msgid.link/20261020203257.230955-6-socketcan@hartkopp.net

> diff --git a/net/can/isotp.c b/net/can/isotp.c
> index 5e1c3971ebfce..8ec37d252557e 100644
> --- a/net/can/isotp.c
> +++ b/net/can/isotp.c

[ ... ]

> @@ -1614,7 +1612,17 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
>  		goto out;
>  	}
>  
> -	dev = dev_get_by_index(net, addr->can_ifindex);
> +	/* 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.
> +	 */
> +	rcu_read_lock();
> +	dev = dev_get_by_index_rcu(net, addr->can_ifindex);
> +	if (dev) {
> +		dev_hold(dev);
> +		WRITE_ONCE(so->dev, dev);
> +	}
> +	rcu_read_unlock();
>  	if (!dev) {
>  		err = -ENODEV;
>  		goto out;
> @@ -1627,7 +1635,12 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
>  		err = -EINVAL;
>  		goto out_put_dev;
>  	}

[Severity: Low]
so->dev is now visible to the lockless check in isotp_notify() before the
remaining checks in isotp_bind() run, and before so->bound is set. The MTU
check can still fail the bind:

	if (READ_ONCE(dev->mtu) < so->ll.mtu) {
		err = -EINVAL;
		goto out_put_dev;
	}

so->dev is only cleared again at out_put_dev.

isotp_bind() no longer holds RTNL. Can a NETDEV_DOWN for the same device
run isotp_notifier()->isotp_notify() inside this window?

The NETDEV_DOWN case only checks READ_ONCE(so->dev) != dev. It does not
look at so->bound or recheck under lock_sock():

	case NETDEV_DOWN:
		sk->sk_err = ENETDOWN;
		if (!sock_flag(sk, SOCK_DEAD))
			sk_error_report(sk);
		break;

Would this set a stale ENETDOWN on a socket that was never bound, whose
bind() then returns -EINVAL? A later successful bind() to another device
(after fixing ll.mtu with CAN_ISOTP_LL_OPTS) would then get that error from
the next recvmsg() or poll().

raw_bind() avoids this. It only publishes ro->bind_dev early, which
raw_notify() uses for NETDEV_UNREGISTER only, and it sets ro->dev after
success. Could isotp use the same approach?

> @@ -1653,15 +1666,17 @@ 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);

[Severity: Low]
This isn't a bug introduced by this patch, but isotp_bind() ignores the
return values of both can_rx_register() calls just above this:

	if (isotp_register_rxid(so))
		can_rx_register(net, dev, rx_id, SINGLE_MASK(rx_id),
				isotp_rcv, sk, sock_i_ino(sk), sk);
	...
	can_rx_register(net, dev, tx_id, SINGLE_MASK(tx_id),
			isotp_rcv_echo, sk, sock_i_ino(sk), sk);

It then sets so->bound = 1 unconditionally.

can_rx_register() returns -ENOMEM if kmem_cache_alloc(rcv_cache,
GFP_KERNEL) fails. Can the socket then report a successful bind() while it
is missing its FC/RX receiver or its echo receiver?

Later, isotp_release() and isotp_notify() would call can_rx_unregister()
for an entry that was never added and hit the "receive list entry not
found" warning. raw_enable_filters() and bcm_rx_setup() check this return
value and unwind.

-ENODEV from the net_eq() check does not look reachable here.
isotp_notify() waits on lock_sock() for NETDEV_UNREGISTER, so dev_net(dev)
cannot change during the registrations. That leaves -ENOMEM as the only
error.

The earlier commit "can: replace ARPHRD_CAN type checks with
can_get_ml_priv()" in this series already notes that isotp_bind() ignores
these return values.

[ ... ]

> diff --git a/net/can/raw.c b/net/can/raw.c
> index dfea48768b231..d07f3bb68cd5c 100644
> --- a/net/can/raw.c
> +++ b/net/can/raw.c

[ ... ]

> @@ -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;

[ ... ]

> -	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.
> +		 */

[ ... ]

> +	}
> +
>  	lock_sock(sk);
>  
> -	err = raw_setsockopt_locked(sock, optname, optval, optlen);
> +	err = raw_setsockopt_locked(sock, optname, optval, optlen,
> +				    filter, &sfilter, count);

[Severity: Medium]
The comment says a stalled copy must not block raw_notify() while it waits
for lock_sock() under RTNL. The early copy only covers CAN_RAW_FILTER,
though. Do the other options still copy from user memory with lock_sock()
held?

In raw_setsockopt_locked(), CAN_RAW_ERR_FILTER still does:

	if (copy_from_sockptr(&err_mask, optval, optlen))
		return -EFAULT;

CAN_RAW_LOOPBACK, CAN_RAW_RECV_OWN_MSGS, CAN_RAW_FD_FRAMES,
CAN_RAW_XL_FRAMES, CAN_RAW_XL_VCID_OPTS and CAN_RAW_JOIN_FILTERS do the
same after lock_sock(sk) is taken here.

raw_getsockopt(CAN_RAW_FILTER) also writes to the user buffer with
lock_sock() held:

	lock_sock(sk);
	...
		if (copy_to_iter(ro->filter, len,
				 &opt->iter_out) != len)
			err = -EFAULT;

Suppose one of these copies stalls on a FUSE-backed mapping while the
socket is bound, or while ro->bind_dev matches the device. Would a
NETDEV_UNREGISTER of that device then leave raw_notify() sleeping in
lock_sock() with RTNL held?

raw_notifier()
  raw_notify()
    lock_sock(sk)   <- waits for the stalled setsockopt/getsockopt

The unregister could come from ip link del of a vcan device in the user's
own network namespace, a namespace move, or a USB unplug.

The new ro->bind_dev hint also adds cases where raw_notify() takes
lock_sock(): a stale bind_dev that matches the unregistered device leads
there too.

Before this patch, raw_setsockopt() held rtnl_lock() itself across these
copies, so overall exposure is lower than before. The new design relies on
lock_sock() never being held across a user copy, though. Should the
remaining copies in raw_setsockopt_locked() and raw_getsockopt() also move
out of the locked section?

isotp_setsockopt() has the same pattern against isotp_notify(), since every
option is copied under lock_sock():

	lock_sock(sk);
	ret = isotp_setsockopt_locked(sock, level, optname, optval, optlen);
	release_sock(sk);

That code predates this patch. With RTNL gone from isotp_bind(), however,
bind relies on lock_sock() alone to serialize with isotp_notify().

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

[Oliver Hartkopp]

On 21.10.26 22:55, Jakub Kicinski wrote:
> This is an AI-generated review of your patch. The human sending this
> email has considered the AI review valid, or at least plausible.
> ---
> can: protect the receive lists with a per-device lock
> 
> This commit adds a spinlock to struct can_dev_rcv_lists. The receive lists
> of a CAN device are now protected per device instead of by the per-netns
> rcvlists_lock, so can_rx_unregister() can find subscriptions after the
> device has moved to another namespace.
> 
> RTNL is dropped from raw_bind(), raw_setsockopt(), raw_release(),
> isotp_bind() and isotp_release(). These paths now use lock_sock() and a
> device pointer published under RCU to serialize against the netdev
> notifier.
> 
> Link: https://lore.kernel.org/linux-can/CEA6A38A-2646-4ADA-95B4-CBAE2F301A8E@doyensec.com/
> Link: https://patch.msgid.link/20261020203257.230955-6-socketcan@hartkopp.net
> 
>> diff --git a/net/can/isotp.c b/net/can/isotp.c
>> index 5e1c3971ebfce..8ec37d252557e 100644
>> --- a/net/can/isotp.c
>> +++ b/net/can/isotp.c
> 
> [ ... ]
> 
>> @@ -1614,7 +1612,17 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
>>   		goto out;
>>   	}
>>   
>> -	dev = dev_get_by_index(net, addr->can_ifindex);
>> +	/* 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.
>> +	 */
>> +	rcu_read_lock();
>> +	dev = dev_get_by_index_rcu(net, addr->can_ifindex);
>> +	if (dev) {
>> +		dev_hold(dev);
>> +		WRITE_ONCE(so->dev, dev);
>> +	}
>> +	rcu_read_unlock();
>>   	if (!dev) {
>>   		err = -ENODEV;
>>   		goto out;
>> @@ -1627,7 +1635,12 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
>>   		err = -EINVAL;
>>   		goto out_put_dev;
>>   	}
> 
> [Severity: Low]
> so->dev is now visible to the lockless check in isotp_notify() before the
> remaining checks in isotp_bind() run, and before so->bound is set. The MTU
> check can still fail the bind:
> 
> 	if (READ_ONCE(dev->mtu) < so->ll.mtu) {
> 		err = -EINVAL;
> 		goto out_put_dev;
> 	}
> 
> so->dev is only cleared again at out_put_dev.
> 
> isotp_bind() no longer holds RTNL. Can a NETDEV_DOWN for the same device
> run isotp_notifier()->isotp_notify() inside this window?
> 
> The NETDEV_DOWN case only checks READ_ONCE(so->dev) != dev. It does not
> look at so->bound or recheck under lock_sock():
> 
> 	case NETDEV_DOWN:
> 		sk->sk_err = ENETDOWN;
> 		if (!sock_flag(sk, SOCK_DEAD))
> 			sk_error_report(sk);
> 		break;
> 
> Would this set a stale ENETDOWN on a socket that was never bound, whose
> bind() then returns -EINVAL? A later successful bind() to another device
> (after fixing ll.mtu with CAN_ISOTP_LL_OPTS) would then get that error from
> the next recvmsg() or poll().
> 
> raw_bind() avoids this. It only publishes ro->bind_dev early, which
> raw_notify() uses for NETDEV_UNREGISTER only, and it sets ro->dev after
> success. Could isotp use the same approach?
> 

Yes, changing the order here to

         rcu_read_lock();
         dev = dev_get_by_index_rcu(net, addr->can_ifindex);
         if (!dev || !can_get_ml_priv(dev))
                 err = -ENODEV;
         else if (READ_ONCE(dev->mtu) < so->ll.mtu)
                 err = -EINVAL;
         if (!err) {
                 dev_hold(dev);
                 WRITE_ONCE(so->dev, dev);
         }
         rcu_read_unlock();
         if (err)
                 goto out;

is a good hint from sashiko-bot and follows the raw_bind() concept.
@Jakub: I've sent a V6 only for this single patch 11/11 here:

Is this ok for you? I think Marc is offline and can not re-spin the PR 
right now.

https://lore.kernel.org/netdev/20261021215456.119268-1-socketcan@hartkopp.net/

>> @@ -1653,15 +1666,17 @@ 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);
> 
> [Severity: Low]
> This isn't a bug introduced by this patch, but isotp_bind() ignores the
> return values of both can_rx_register() calls just above this:
> 
> 	if (isotp_register_rxid(so))
> 		can_rx_register(net, dev, rx_id, SINGLE_MASK(rx_id),
> 				isotp_rcv, sk, sock_i_ino(sk), sk);
> 	...
> 	can_rx_register(net, dev, tx_id, SINGLE_MASK(tx_id),
> 			isotp_rcv_echo, sk, sock_i_ino(sk), sk);
> 
> It then sets so->bound = 1 unconditionally.
> 
> can_rx_register() returns -ENOMEM if kmem_cache_alloc(rcv_cache,
> GFP_KERNEL) fails. Can the socket then report a successful bind() while it
> is missing its FC/RX receiver or its echo receiver?
> 
> Later, isotp_release() and isotp_notify() would call can_rx_unregister()
> for an entry that was never added and hit the "receive list entry not
> found" warning. raw_enable_filters() and bcm_rx_setup() check this return
> value and unwind.
> 
> -ENODEV from the net_eq() check does not look reachable here.
> isotp_notify() waits on lock_sock() for NETDEV_UNREGISTER, so dev_net(dev)
> cannot change during the registrations. That leaves -ENOMEM as the only
> error.
> 
> The earlier commit "can: replace ARPHRD_CAN type checks with
> can_get_ml_priv()" in this series already notes that isotp_bind() ignores
> these return values.

Right.

This is a pre-existing issue and will be fixed separately. With the
can_get_ml_priv() check in isotp_bind() and the namespace change being
serialized via lock_sock() against isotp_notify(), the only remaining
error from can_rx_register() is -ENOMEM from the GFP_KERNEL allocation
of the receiver. The fix will be addressed in the next net-next cycle.
As this is an improvement for a very unlikely allocation failure, it is
not intended for stable.

> 
> [ ... ]
> 
>> diff --git a/net/can/raw.c b/net/can/raw.c
>> index dfea48768b231..d07f3bb68cd5c 100644
>> --- a/net/can/raw.c
>> +++ b/net/can/raw.c
> 
> [ ... ]
> 
>> @@ -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;
> 
> [ ... ]
> 
>> -	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.
>> +		 */
> 
> [ ... ]
> 
>> +	}
>> +
>>   	lock_sock(sk);
>>   
>> -	err = raw_setsockopt_locked(sock, optname, optval, optlen);
>> +	err = raw_setsockopt_locked(sock, optname, optval, optlen,
>> +				    filter, &sfilter, count);
> 
> [Severity: Medium]
> The comment says a stalled copy must not block raw_notify() while it waits
> for lock_sock() under RTNL. The early copy only covers CAN_RAW_FILTER,
> though. Do the other options still copy from user memory with lock_sock()
> held?
> 
> In raw_setsockopt_locked(), CAN_RAW_ERR_FILTER still does:
> 
> 	if (copy_from_sockptr(&err_mask, optval, optlen))
> 		return -EFAULT;
> 
> CAN_RAW_LOOPBACK, CAN_RAW_RECV_OWN_MSGS, CAN_RAW_FD_FRAMES,
> CAN_RAW_XL_FRAMES, CAN_RAW_XL_VCID_OPTS and CAN_RAW_JOIN_FILTERS do the
> same after lock_sock(sk) is taken here.
> 
> raw_getsockopt(CAN_RAW_FILTER) also writes to the user buffer with
> lock_sock() held:
> 
> 	lock_sock(sk);
> 	...
> 		if (copy_to_iter(ro->filter, len,
> 				 &opt->iter_out) != len)
> 			err = -EFAULT;
> 
> Suppose one of these copies stalls on a FUSE-backed mapping while the
> socket is bound, or while ro->bind_dev matches the device. Would a
> NETDEV_UNREGISTER of that device then leave raw_notify() sleeping in
> lock_sock() with RTNL held?
> 
> raw_notifier()
>    raw_notify()
>      lock_sock(sk)   <- waits for the stalled setsockopt/getsockopt
> 
> The unregister could come from ip link del of a vcan device in the user's
> own network namespace, a namespace move, or a USB unplug.
> 
> The new ro->bind_dev hint also adds cases where raw_notify() takes
> lock_sock(): a stale bind_dev that matches the unregistered device leads
> there too.
> 
> Before this patch, raw_setsockopt() held rtnl_lock() itself across these
> copies, so overall exposure is lower than before. The new design relies on
> lock_sock() never being held across a user copy, though. Should the
> remaining copies in raw_setsockopt_locked() and raw_getsockopt() also move
> out of the locked section?
> 
> isotp_setsockopt() has the same pattern against isotp_notify(), since every
> option is copied under lock_sock():
> 
> 	lock_sock(sk);
> 	ret = isotp_setsockopt_locked(sock, level, optname, optval, optlen);
> 	release_sock(sk);
> 
> That code predates this patch. With RTNL gone from isotp_bind(), however,
> bind relies on lock_sock() alone to serialize with isotp_notify().

Right, the early copy in raw_setsockopt() only covers CAN_RAW_FILTER.
Before this patch, raw_setsockopt() held RTNL itself across all user
space copies, so this patch already improves the current situation. The
complete rework that moves all remaining user space copies in raw.c and
isotp.c out of lock_sock() will be addressed in the next net-next cycle.
This is an improvement and not intended for stable.

Best regards,
Oliver

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

[Marc Kleine-Budde]

[-- Attachment #1: Type: text/plain, Size: 687 bytes --]

On 21.10.2026 23:59:17, Oliver Hartkopp wrote:
[...]>
> is a good hint from sashiko-bot and follows the raw_bind() concept.
> @Jakub: I've sent a V6 only for this single patch 11/11 here:
>
> Is this ok for you? I think Marc is offline and can not re-spin the PR right
> now.
>
> https://lore.kernel.org/netdev/20261021215456.119268-1-socketcan@hartkopp.net/

Give me a sec, I'm preparing the new PR.

Marc

--
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |

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

[Oliver Hartkopp]

On 22.10.26 01:05, Marc Kleine-Budde wrote:
> On 21.10.2026 23:59:17, Oliver Hartkopp wrote:
> [...]>
>> is a good hint from sashiko-bot and follows the raw_bind() concept.
>> @Jakub: I've sent a V6 only for this single patch 11/11 here:
>>
>> Is this ok for you? I think Marc is offline and can not re-spin the PR right
>> now.
>>
>> https://lore.kernel.org/netdev/20261021215456.119268-1-socketcan@hartkopp.net/
> 
> Give me a sec, I'm preparing the new PR.
> 
> Marc
> 
Thanks Marc!

PR can-next 2026-10-22 is here:

https://lore.kernel.org/netdev/20261021231130.2085690-1-mkl@pengutronix.de/

Many thanks,
Oliver

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

[Marc Kleine-Budde]

[-- Attachment #1: Type: text/plain, Size: 1144 bytes --]

On 21.10.2026 23:59:17, Oliver Hartkopp wrote:
> Yes, changing the order here to
>
>         rcu_read_lock();
>         dev = dev_get_by_index_rcu(net, addr->can_ifindex);
>         if (!dev || !can_get_ml_priv(dev))
>                 err = -ENODEV;
>         else if (READ_ONCE(dev->mtu) < so->ll.mtu)
>                 err = -EINVAL;
>         if (!err) {
>                 dev_hold(dev);
>                 WRITE_ONCE(so->dev, dev);
>         }
>         rcu_read_unlock();
>         if (err)
>                 goto out;
>
> is a good hint from sashiko-bot and follows the raw_bind() concept.
> @Jakub: I've sent a V6 only for this single patch 11/11 here:
>
> Is this ok for you? I think Marc is offline and can not re-spin the PR right
> now.
>
> https://lore.kernel.org/netdev/20261021215456.119268-1-socketcan@hartkopp.net/

pw-bot: cr

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |

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

[Marc Kleine-Budde]

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

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

[Marc Kleine-Budde]

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 the callers 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().

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/20261019152741.54854-6-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           |  40 +++++++----
 net/can/bcm.c              |  43 ++++-------
 net/can/isotp.c            |  40 +++++++----
 net/can/raw.c              | 142 ++++++++++++++++++++++++-------------
 6 files changed, 161 insertions(+), 109 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..ef7aefdf7b23 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 rcv_lists_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..bf612c4b983d 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 +513,13 @@ 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 is the namespace that has been used for can_rx_register().
+ *  It selects the 'any' CAN device lists for @dev == NULL and is used for
+ *  the receive list statistics.
  */
 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 +533,10 @@ 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 +556,26 @@ 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 +832,7 @@ 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..5ae55ed28d57 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) {
@@ -1614,7 +1612,17 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
 		goto out;
 	}
 
-	dev = dev_get_by_index(net, addr->can_ifindex);
+	/* 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.
+	 */
+	rcu_read_lock();
+	dev = dev_get_by_index_rcu(net, addr->can_ifindex);
+	if (dev) {
+		dev_hold(dev);
+		WRITE_ONCE(so->dev, dev);
+	}
+	rcu_read_unlock();
 	if (!dev) {
 		err = -ENODEV;
 		goto out;
@@ -1627,7 +1635,7 @@ static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int l
 		err = -EINVAL;
 		goto out_put_dev;
 	}
-	if (!(dev->flags & IFF_UP))
+	if (!(READ_ONCE(dev->flags) & IFF_UP))
 		notify_enetdown = 1;
 
 	ifindex = dev->ifindex;
@@ -1653,15 +1661,17 @@ 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() */
+	/* the published so->dev is only valid for a successful bind() */
+	if (err)
+		WRITE_ONCE(so->dev, NULL);
+
+	/* remove reference from the device lookup */
 	dev_put(dev);
 out:
 	release_sock(sk);
-	rtnl_unlock();
 
 	if (notify_enetdown) {
 		sk->sk_err = ENETDOWN;
@@ -1864,12 +1874,18 @@ 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)
+	/* 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 +1901,7 @@ 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..0d8edfa772fb 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 +309,28 @@ 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)
+	/* 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 +342,7 @@ 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 +397,7 @@ 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 +448,15 @@ 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 +475,6 @@ 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 +497,25 @@ 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;
@@ -496,7 +525,7 @@ static int raw_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int len
 			goto out_put_dev;
 		}
 
-		if (!(dev->flags & IFF_UP))
+		if (!(READ_ONCE(dev->flags) & IFF_UP))
 			notify_enetdown = 1;
 
 		ifindex = dev->ifindex;
@@ -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 +557,15 @@ 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);
 	}
 
 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 +594,41 @@ 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 +642,7 @@ 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 +658,10 @@ 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 +763,47 @@ 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

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

[netdev-bot+sashiko]

Thank you for your contribution! Sashiko AI review found 3 potential
issue(s) to consider.

Critical: 0 · High: 0 · Medium: 1 · Low: 2

If you believe none of the issues are legitimate, please reply to each
issue of Medium severity or higher and explain why the AI is wrong.
If any of them are legitimate and you plan to respin, please let patchwork
know by including "pw-bot: cr" as a separate line at the end of your reply
(one such reply per series is enough).

- [Medium] raw_bind() no longer holds RTNL, so the socket can miss a
  NETDEV_DOWN that arrives while it is binding.
- [Low] The commit message says "the callers pass the namespace that has
  been used for can_rx_register()", and the new kernel-doc of…
- [Low] The new comment on netns_can.rcvlists_lock in
  include/net/netns/can.h says it "protects rcv_lists_stats".

--

can: protect the receive lists with a per-device lock

This commit adds a spinlock to struct can_dev_rcv_lists. The receive lists
of a CAN device are now protected per device instead of by the per-netns
rcvlists_lock, so can_rx_unregister() still finds subscriptions after the
device has moved to another namespace. It also drops RTNL from raw_bind(),
raw_setsockopt(), raw_release(), isotp_bind() and isotp_release(), and
relies on lock_sock() plus a device pointer published inside the RCU
lookup to serialize with the netdev notifiers.

Link: https://lore.kernel.org/linux-can/CEA6A38A-2646-4ADA-95B4-CBAE2F301A8E@doyensec.com/
Link: https://patch.msgid.link/20261019152741.54854-6-socketcan@hartkopp.net

> diff --git a/include/net/netns/can.h b/include/net/netns/can.h
> index 48b79f7e6236..ef7aefdf7b23 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 rcv_lists_stats */

[Severity: Low]
This isn't a bug, but is this comment accurate? The lock only serializes
the rcv_entries and rcv_entries_max updates in can_rx_register() and
can_rx_unregister().

can_init_stats() in net/can/proc.c updates other fields of the same
structure without taking rcvlists_lock. It runs from the stats timer, or
from the reset_stats proc read when the timer is disabled:

net/can/proc.c:can_init_stats() {
    ...
	rcv_lists_stats->stats_reset++;

	if (user_reset) {
		user_reset = 0;
		rcv_lists_stats->user_reset++;
	}
}

can_stats_proc_show() also reads these counters without the lock.

Could the comment name rcv_entries and rcv_entries_max specifically?

[ ... ]

> diff --git a/net/can/af_can.c b/net/can/af_can.c
> index d97f85fc3232..bf612c4b983d 100644
> --- a/net/can/af_can.c
> +++ b/net/can/af_can.c

[ ... ]

> @@ -509,6 +513,13 @@ 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 is the namespace that has been used for can_rx_register().
> + *  It selects the 'any' CAN device lists for @dev == NULL and is used for
> + *  the receive list statistics.
>   */

[Severity: Low]
The new kernel-doc says @net is the namespace that was used for
can_rx_register(). The commit message says the same: "the callers pass
the namespace that has been used for can_rx_register()".

Does j1939 follow this? It reads dev_net(ndev) again at unregister time:

net/can/j1939/main.c:j1939_can_rx_register() {
    ...
	ret = can_rx_register(dev_net(ndev), ndev, J1939_CAN_ID, J1939_CAN_MASK,
			      j1939_can_recv, priv, 0, NULL);
    ...
}

net/can/j1939/main.c:j1939_can_rx_unregister() {
    ...
	can_rx_unregister(dev_net(ndev), ndev, J1939_CAN_ID, J1939_CAN_MASK,
			  j1939_can_recv, priv);
    ...
}

A j1939 registration can outlive a namespace move. j1939_sk_bind() does
not hold RTNL. It calls j1939_netdev_start(), which registers with the old
namespace, before it calls j1939_jsk_add().

Suppose the NETDEV_UNREGISTER from __dev_change_net_namespace() runs
j1939_sk_netdev_event_unregister() in that window. The socket is not
J1939_SOCK_BOUND yet, so it is skipped and the registration survives the
move. The final release then passes the new namespace:

j1939_netdev_stop()
  __j1939_rx_release()
    j1939_can_rx_unregister()
      can_rx_unregister(dev_net(ndev), ...)

The receiver is still found through the per-device lists. However,
rcv_entries is decremented in the new namespace's rcv_lists_stats
(clamped at 0) and stays elevated in the old one. This accounting matches
the behaviour before the patch.

Should j1939_priv store the registration namespace (with a netns
reference)? Or should the kernel-doc and commit message describe a looser
rule?

[ ... ]

> diff --git a/net/can/raw.c b/net/can/raw.c
> index dfea48768b23..0d8edfa772fb 100644
> --- a/net/can/raw.c
> +++ b/net/can/raw.c

[ ... ]

> @@ -305,16 +309,28 @@ 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)
> +	/* 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;

[Severity: Medium]
Can a NETDEV_DOWN be lost while raw_bind() is running? The bind_dev hint
is only checked for NETDEV_UNREGISTER, and raw_bind() no longer holds
RTNL.

raw_bind() now runs these steps in order:

    smp_store_release(&ro->bind_dev, dev);
    ...
    if (!(READ_ONCE(dev->flags) & IFF_UP))   /* device still up here */
        notify_enetdown = 1;
    ...
    err = raw_enable_allfilters(sock_net(sk), dev, sk);  /* cond_resched() */
    ...
    WRITE_ONCE(ro->dev, dev);

Suppose dev_close() runs after the IFF_UP check but before ro->dev is
published. raw_notifier()->raw_notify() then sees ro->dev != dev with
msg == NETDEV_DOWN, so it returns at the check above and never reaches
case NETDEV_DOWN. raw_bind() finishes with notify_enetdown == 0.

The socket ends up bound to a down interface, and sk_err = ENETDOWN /
sk_error_report() is never raised. Before this patch, rtnl_lock() in
raw_bind() kept dev_close() out of this window.

isotp_bind() publishes so->dev before it reads IFF_UP, so it does not seem
to have this problem.

Could raw_notify() also check bind_dev for NETDEV_DOWN? Alternatively,
raw_bind() could publish ro->dev before the IFF_UP check.

[ ... ]

-- 
Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20261019170834.1727150-2-mkl%40pengutronix.de

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

[Oliver Hartkopp]

On 20.10.26 19:11, netdev-bot+sashiko@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 3 potential
> issue(s) to consider.
> 
> Critical: 0 · High: 0 · Medium: 1 · Low: 2
> 
> If you believe none of the issues are legitimate, please reply to each
> issue of Medium severity or higher and explain why the AI is wrong.
> If any of them are legitimate and you plan to respin, please let patchwork
> know by including "pw-bot: cr" as a separate line at the end of your reply
> (one such reply per series is enough).
> 
> - [Medium] raw_bind() no longer holds RTNL, so the socket can miss a
>    NETDEV_DOWN that arrives while it is binding.
> - [Low] The commit message says "the callers pass the namespace that has
>    been used for can_rx_register()", and the new kernel-doc of…
> - [Low] The new comment on netns_can.rcvlists_lock in
>    include/net/netns/can.h says it "protects rcv_lists_stats".
> 

Thanks for the review.

[Medium] NETDEV_DOWN during raw_bind():

The window exists, but it only affects a down transition in the middle
of raw_bind(). Missing the asynchronous ENETDOWN there is harmless and
not worth an additional barrier pair in raw_bind() and raw_notify():

- Every transmission on a CAN_RAW socket goes through can_send(), which
   checks IFF_UP and returns -ENETDOWN to sendmsg(). So the state is
   reported reliably on every send attempt.

- The missed notification does not affect the binding: the CAN_RAW
   socket stays bound and its filters stay registered across down/up,
   and frames are received again once the interface is up.

- Applications can not rely on this notification anyway: a CAN_RAW
   socket bound to all CAN interfaces (ifindex 0) never gets ENETDOWN.
   Applications that need the link state have to track it via
   rtnetlink, not via the CAN socket.

[Low] rcvlists_lock comment / j1939 @net: These are documentation
details; the j1939 statistics behaviour is unchanged by this patch, as
noted in the patch description.

Best regards,
Oliver


> --
> 
> can: protect the receive lists with a per-device lock
> 
> This commit adds a spinlock to struct can_dev_rcv_lists. The receive lists
> of a CAN device are now protected per device instead of by the per-netns
> rcvlists_lock, so can_rx_unregister() still finds subscriptions after the
> device has moved to another namespace. It also drops RTNL from raw_bind(),
> raw_setsockopt(), raw_release(), isotp_bind() and isotp_release(), and
> relies on lock_sock() plus a device pointer published inside the RCU
> lookup to serialize with the netdev notifiers.
> 
> Link: https://lore.kernel.org/linux-can/CEA6A38A-2646-4ADA-95B4-CBAE2F301A8E@doyensec.com/
> Link: https://patch.msgid.link/20261019152741.54854-6-socketcan@hartkopp.net
> 
>> diff --git a/include/net/netns/can.h b/include/net/netns/can.h
>> index 48b79f7e6236..ef7aefdf7b23 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 rcv_lists_stats */
> 
> [Severity: Low]
> This isn't a bug, but is this comment accurate? The lock only serializes
> the rcv_entries and rcv_entries_max updates in can_rx_register() and
> can_rx_unregister().
> 
> can_init_stats() in net/can/proc.c updates other fields of the same
> structure without taking rcvlists_lock. It runs from the stats timer, or
> from the reset_stats proc read when the timer is disabled:
> 
> net/can/proc.c:can_init_stats() {
>      ...
> 	rcv_lists_stats->stats_reset++;
> 
> 	if (user_reset) {
> 		user_reset = 0;
> 		rcv_lists_stats->user_reset++;
> 	}
> }
> 
> can_stats_proc_show() also reads these counters without the lock.
> 
> Could the comment name rcv_entries and rcv_entries_max specifically?
> 
> [ ... ]
> 
>> diff --git a/net/can/af_can.c b/net/can/af_can.c
>> index d97f85fc3232..bf612c4b983d 100644
>> --- a/net/can/af_can.c
>> +++ b/net/can/af_can.c
> 
> [ ... ]
> 
>> @@ -509,6 +513,13 @@ 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 is the namespace that has been used for can_rx_register().
>> + *  It selects the 'any' CAN device lists for @dev == NULL and is used for
>> + *  the receive list statistics.
>>    */
> 
> [Severity: Low]
> The new kernel-doc says @net is the namespace that was used for
> can_rx_register(). The commit message says the same: "the callers pass
> the namespace that has been used for can_rx_register()".
> 
> Does j1939 follow this? It reads dev_net(ndev) again at unregister time:
> 
> net/can/j1939/main.c:j1939_can_rx_register() {
>      ...
> 	ret = can_rx_register(dev_net(ndev), ndev, J1939_CAN_ID, J1939_CAN_MASK,
> 			      j1939_can_recv, priv, 0, NULL);
>      ...
> }
> 
> net/can/j1939/main.c:j1939_can_rx_unregister() {
>      ...
> 	can_rx_unregister(dev_net(ndev), ndev, J1939_CAN_ID, J1939_CAN_MASK,
> 			  j1939_can_recv, priv);
>      ...
> }
> 
> A j1939 registration can outlive a namespace move. j1939_sk_bind() does
> not hold RTNL. It calls j1939_netdev_start(), which registers with the old
> namespace, before it calls j1939_jsk_add().
> 
> Suppose the NETDEV_UNREGISTER from __dev_change_net_namespace() runs
> j1939_sk_netdev_event_unregister() in that window. The socket is not
> J1939_SOCK_BOUND yet, so it is skipped and the registration survives the
> move. The final release then passes the new namespace:
> 
> j1939_netdev_stop()
>    __j1939_rx_release()
>      j1939_can_rx_unregister()
>        can_rx_unregister(dev_net(ndev), ...)
> 
> The receiver is still found through the per-device lists. However,
> rcv_entries is decremented in the new namespace's rcv_lists_stats
> (clamped at 0) and stays elevated in the old one. This accounting matches
> the behaviour before the patch.
> 
> Should j1939_priv store the registration namespace (with a netns
> reference)? Or should the kernel-doc and commit message describe a looser
> rule?
> 
> [ ... ]
> 
>> diff --git a/net/can/raw.c b/net/can/raw.c
>> index dfea48768b23..0d8edfa772fb 100644
>> --- a/net/can/raw.c
>> +++ b/net/can/raw.c
> 
> [ ... ]
> 
>> @@ -305,16 +309,28 @@ 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)
>> +	/* 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;
> 
> [Severity: Medium]
> Can a NETDEV_DOWN be lost while raw_bind() is running? The bind_dev hint
> is only checked for NETDEV_UNREGISTER, and raw_bind() no longer holds
> RTNL.
> 
> raw_bind() now runs these steps in order:
> 
>      smp_store_release(&ro->bind_dev, dev);
>      ...
>      if (!(READ_ONCE(dev->flags) & IFF_UP))   /* device still up here */
>          notify_enetdown = 1;
>      ...
>      err = raw_enable_allfilters(sock_net(sk), dev, sk);  /* cond_resched() */
>      ...
>      WRITE_ONCE(ro->dev, dev);
> 
> Suppose dev_close() runs after the IFF_UP check but before ro->dev is
> published. raw_notifier()->raw_notify() then sees ro->dev != dev with
> msg == NETDEV_DOWN, so it returns at the check above and never reaches
> case NETDEV_DOWN. raw_bind() finishes with notify_enetdown == 0.
> 
> The socket ends up bound to a down interface, and sk_err = ENETDOWN /
> sk_error_report() is never raised. Before this patch, rtnl_lock() in
> raw_bind() kept dev_close() out of this window.
> 
> isotp_bind() publishes so->dev before it reads IFF_UP, so it does not seem
> to have this problem.
> 
> Could raw_notify() also check bind_dev for NETDEV_DOWN? Alternatively,
> raw_bind() could publish ro->dev before the IFF_UP check.
> 
> [ ... ]
> 

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

[Oliver Hartkopp]

On 20.10.26 21:00, Oliver Hartkopp wrote:
> 
> 
> On 20.10.26 19:11, netdev-bot+sashiko@kernel.org wrote:
>> Thank you for your contribution! Sashiko AI review found 3 potential
>> issue(s) to consider.
>>
>> Critical: 0 · High: 0 · Medium: 1 · Low: 2
>>
>> If you believe none of the issues are legitimate, please reply to each
>> issue of Medium severity or higher and explain why the AI is wrong.
>> If any of them are legitimate and you plan to respin, please let 
>> patchwork
>> know by including "pw-bot: cr" as a separate line at the end of your 
>> reply
>> (one such reply per series is enough).
>>
>> - [Medium] raw_bind() no longer holds RTNL, so the socket can miss a
>>    NETDEV_DOWN that arrives while it is binding.
>> - [Low] The commit message says "the callers pass the namespace that has
>>    been used for can_rx_register()", and the new kernel-doc of…
>> - [Low] The new comment on netns_can.rcvlists_lock in
>>    include/net/netns/can.h says it "protects rcv_lists_stats".
>>
> 
> Thanks for the review.
> 
> [Medium] NETDEV_DOWN during raw_bind():
> 
> The window exists, but it only affects a down transition in the middle
> of raw_bind(). Missing the asynchronous ENETDOWN there is harmless and
> not worth an additional barrier pair in raw_bind() and raw_notify():


I did a closer look into it.

Although the missing of -ENETDOWN in raw_bind() is not a big issue it 
changes the former behaviour which is more relevant for reading from the 
CAN_RAW socket than writing to it.

 >> isotp_bind() publishes so->dev before it reads IFF_UP, so it does not
 >> seem to have this problem.

In fact both raw and isotp need smp_mb() to have the correct ordering.
I would bet a beer sashiko-bot would have remarked it next time :-/

While at it I also fixed the low severity commit and documentation 
remarks from sashiko-bot in patch 5 and patch 4.

New v5 patch set with updated cover letter for can-next is here:

https://lore.kernel.org/linux-can/20261020203257.230955-1-socketcan@hartkopp.net/

Best regards,
Oliver

pw-bot: cr

> 
> - Every transmission on a CAN_RAW socket goes through can_send(), which
>    checks IFF_UP and returns -ENETDOWN to sendmsg(). So the state is
>    reported reliably on every send attempt.
> 
> - The missed notification does not affect the binding: the CAN_RAW
>    socket stays bound and its filters stay registered across down/up,
>    and frames are received again once the interface is up.
> 
> - Applications can not rely on this notification anyway: a CAN_RAW
>    socket bound to all CAN interfaces (ifindex 0) never gets ENETDOWN.
>    Applications that need the link state have to track it via
>    rtnetlink, not via the CAN socket.
> 
> [Low] rcvlists_lock comment / j1939 @net: These are documentation
> details; the j1939 statistics behaviour is unchanged by this patch, as
> noted in the patch description.
> 
> Best regards,
> Oliver
> 
> 
>> -- 
>>
>> can: protect the receive lists with a per-device lock
>>
>> This commit adds a spinlock to struct can_dev_rcv_lists. The receive 
>> lists
>> of a CAN device are now protected per device instead of by the per-netns
>> rcvlists_lock, so can_rx_unregister() still finds subscriptions after the
>> device has moved to another namespace. It also drops RTNL from 
>> raw_bind(),
>> raw_setsockopt(), raw_release(), isotp_bind() and isotp_release(), and
>> relies on lock_sock() plus a device pointer published inside the RCU
>> lookup to serialize with the netdev notifiers.
>>
>> Link: https://lore.kernel.org/linux-can/CEA6A38A-2646-4ADA-95B4- 
>> CBAE2F301A8E@doyensec.com/
>> Link: https://patch.msgid.link/20261019152741.54854-6- 
>> socketcan@hartkopp.net
>>
>>> diff --git a/include/net/netns/can.h b/include/net/netns/can.h
>>> index 48b79f7e6236..ef7aefdf7b23 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 rcv_lists_stats */
>>
>> [Severity: Low]
>> This isn't a bug, but is this comment accurate? The lock only serializes
>> the rcv_entries and rcv_entries_max updates in can_rx_register() and
>> can_rx_unregister().
>>
>> can_init_stats() in net/can/proc.c updates other fields of the same
>> structure without taking rcvlists_lock. It runs from the stats timer, or
>> from the reset_stats proc read when the timer is disabled:
>>
>> net/can/proc.c:can_init_stats() {
>>      ...
>>     rcv_lists_stats->stats_reset++;
>>
>>     if (user_reset) {
>>         user_reset = 0;
>>         rcv_lists_stats->user_reset++;
>>     }
>> }
>>
>> can_stats_proc_show() also reads these counters without the lock.
>>
>> Could the comment name rcv_entries and rcv_entries_max specifically?
>>
>> [ ... ]
>>
>>> diff --git a/net/can/af_can.c b/net/can/af_can.c
>>> index d97f85fc3232..bf612c4b983d 100644
>>> --- a/net/can/af_can.c
>>> +++ b/net/can/af_can.c
>>
>> [ ... ]
>>
>>> @@ -509,6 +513,13 @@ 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 is the namespace that has been used for 
>>> can_rx_register().
>>> + *  It selects the 'any' CAN device lists for @dev == NULL and is 
>>> used for
>>> + *  the receive list statistics.
>>>    */
>>
>> [Severity: Low]
>> The new kernel-doc says @net is the namespace that was used for
>> can_rx_register(). The commit message says the same: "the callers pass
>> the namespace that has been used for can_rx_register()".
>>
>> Does j1939 follow this? It reads dev_net(ndev) again at unregister time:
>>
>> net/can/j1939/main.c:j1939_can_rx_register() {
>>      ...
>>     ret = can_rx_register(dev_net(ndev), ndev, J1939_CAN_ID, 
>> J1939_CAN_MASK,
>>                   j1939_can_recv, priv, 0, NULL);
>>      ...
>> }
>>
>> net/can/j1939/main.c:j1939_can_rx_unregister() {
>>      ...
>>     can_rx_unregister(dev_net(ndev), ndev, J1939_CAN_ID, J1939_CAN_MASK,
>>               j1939_can_recv, priv);
>>      ...
>> }
>>
>> A j1939 registration can outlive a namespace move. j1939_sk_bind() does
>> not hold RTNL. It calls j1939_netdev_start(), which registers with the 
>> old
>> namespace, before it calls j1939_jsk_add().
>>
>> Suppose the NETDEV_UNREGISTER from __dev_change_net_namespace() runs
>> j1939_sk_netdev_event_unregister() in that window. The socket is not
>> J1939_SOCK_BOUND yet, so it is skipped and the registration survives the
>> move. The final release then passes the new namespace:
>>
>> j1939_netdev_stop()
>>    __j1939_rx_release()
>>      j1939_can_rx_unregister()
>>        can_rx_unregister(dev_net(ndev), ...)
>>
>> The receiver is still found through the per-device lists. However,
>> rcv_entries is decremented in the new namespace's rcv_lists_stats
>> (clamped at 0) and stays elevated in the old one. This accounting matches
>> the behaviour before the patch.
>>
>> Should j1939_priv store the registration namespace (with a netns
>> reference)? Or should the kernel-doc and commit message describe a looser
>> rule?
>>
>> [ ... ]
>>
>>> diff --git a/net/can/raw.c b/net/can/raw.c
>>> index dfea48768b23..0d8edfa772fb 100644
>>> --- a/net/can/raw.c
>>> +++ b/net/can/raw.c
>>
>> [ ... ]
>>
>>> @@ -305,16 +309,28 @@ 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)
>>> +    /* 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;
>>
>> [Severity: Medium]
>> Can a NETDEV_DOWN be lost while raw_bind() is running? The bind_dev hint
>> is only checked for NETDEV_UNREGISTER, and raw_bind() no longer holds
>> RTNL.
>>
>> raw_bind() now runs these steps in order:
>>
>>      smp_store_release(&ro->bind_dev, dev);
>>      ...
>>      if (!(READ_ONCE(dev->flags) & IFF_UP))   /* device still up here */
>>          notify_enetdown = 1;
>>      ...
>>      err = raw_enable_allfilters(sock_net(sk), dev, sk);  /* 
>> cond_resched() */
>>      ...
>>      WRITE_ONCE(ro->dev, dev);
>>
>> Suppose dev_close() runs after the IFF_UP check but before ro->dev is
>> published. raw_notifier()->raw_notify() then sees ro->dev != dev with
>> msg == NETDEV_DOWN, so it returns at the check above and never reaches
>> case NETDEV_DOWN. raw_bind() finishes with notify_enetdown == 0.
>>
>> The socket ends up bound to a down interface, and sk_err = ENETDOWN /
>> sk_error_report() is never raised. Before this patch, rtnl_lock() in
>> raw_bind() kept dev_close() out of this window.
>>
>> isotp_bind() publishes so->dev before it reads IFF_UP, so it does not 
>> seem
>> to have this problem.
>>
>> Could raw_notify() also check bind_dev for NETDEV_DOWN? Alternatively,
>> raw_bind() could publish ro->dev before the IFF_UP check.
>>
>> [ ... ]
>>
> 
>