[PATCH v7] net/ncsi: Fix Use-After-Free in NCSI teardown using synchronize_rcu

[Wong Boon Jhee <wongboonjhee52@gmail.com>]

NCSI device teardown can free packages and channels while RCU readers,
including Netlink handlers, are still using them. Unlink the device from
the global list and wait for RCU readers before freeing its state.

Protect Netlink lookups and VLAN callbacks against concurrent teardown.
Synchronously stop channel-monitor timers before freeing their channels,
including when a timer callback has already cleared the enabled flag.
Remove VLAN entries with RCU-safe list deletion and deferred freeing.

Fixes: 2d283bdd079c ("net/ncsi: Resource management")

Signed-off-by: Wong Boon Jhee <wongboonjhee52@gmail.com>
---
v6 -> v7:
- Protect VLAN callbacks from concurrent device teardown and defer VLAN
  entry freeing until RCU readers have completed.
- Synchronize channel-monitor timers even if the callback already cleared
  the enabled flag.
- Use borrowed socket network namespaces in Netlink handlers; remove
  unrelated VLAN and request cleanup from teardown.

 net/ncsi/internal.h     |  1 +
 net/ncsi/ncsi-manage.c  | 96 +++++++++++++++++++++++++++++++----------
 net/ncsi/ncsi-netlink.c | 91 ++++++++++++++++++++++++++++----------
 3 files changed, 142 insertions(+), 46 deletions(-)

diff --git a/net/ncsi/internal.h b/net/ncsi/internal.h
index adee6dcabdc3..d9f0eadc7a24 100644
--- a/net/ncsi/internal.h
+++ b/net/ncsi/internal.h
@@ -310,6 +310,7 @@ enum {
 
 struct vlan_vid {
 	struct list_head list;
+	struct rcu_head rcu;
 	__be16 proto;
 	u16 vid;
 };
diff --git a/net/ncsi/ncsi-manage.c b/net/ncsi/ncsi-manage.c
index 54d0df0a9efe..c3d3a448a07c 100644
--- a/net/ncsi/ncsi-manage.c
+++ b/net/ncsi/ncsi-manage.c
@@ -10,6 +10,7 @@
 #include <linux/skbuff.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/mutex.h>
 
 #include <net/ncsi.h>
 #include <net/net_namespace.h>
@@ -24,6 +25,7 @@
 
 LIST_HEAD(ncsi_dev_list);
 DEFINE_SPINLOCK(ncsi_dev_lock);
+static DEFINE_MUTEX(ncsi_dev_mutex);
 
 bool ncsi_channel_has_link(struct ncsi_channel *channel)
 {
@@ -182,13 +184,10 @@ void ncsi_stop_channel_monitor(struct ncsi_channel *nc)
 	unsigned long flags;
 
 	spin_lock_irqsave(&nc->lock, flags);
-	if (!nc->monitor.enabled) {
-		spin_unlock_irqrestore(&nc->lock, flags);
-		return;
-	}
 	nc->monitor.enabled = false;
 	spin_unlock_irqrestore(&nc->lock, flags);
 
+	/* The callback may have cleared enabled and still be running. */
 	timer_delete_sync(&nc->monitor.timer);
 }
 
@@ -1669,37 +1668,49 @@ int ncsi_vlan_rx_add_vid(struct net_device *dev, __be16 proto, u16 vid)
 	struct vlan_vid *vlan;
 	struct ncsi_dev *nd;
 	bool found = false;
+	int ret;
 
 	if (vid == 0)
 		return 0;
 
+	mutex_lock(&ncsi_dev_mutex);
+	rcu_read_lock();
 	nd = ncsi_find_dev(dev);
+	rcu_read_unlock();
 	if (!nd) {
 		netdev_warn(dev, "NCSI: No net_device?\n");
-		return 0;
+		ret = 0;
+		goto out_unlock;
 	}
 
 	ndp = TO_NCSI_DEV_PRIV(nd);
 
 	/* Add the VLAN id to our internal list */
+	rcu_read_lock();
 	list_for_each_entry_rcu(vlan, &ndp->vlan_vids, list) {
 		n_vids++;
 		if (vlan->vid == vid) {
 			netdev_dbg(dev, "NCSI: vid %u already registered\n",
 				   vid);
-			return 0;
+			rcu_read_unlock();
+			ret = 0;
+			goto out_unlock;
 		}
 	}
+	rcu_read_unlock();
 	if (n_vids >= NCSI_MAX_VLAN_VIDS) {
 		netdev_warn(dev,
 			    "tried to add vlan id %u but NCSI max already registered (%u)\n",
 			    vid, NCSI_MAX_VLAN_VIDS);
-		return -ENOSPC;
+		ret = -ENOSPC;
+		goto out_unlock;
 	}
 
 	vlan = kzalloc_obj(*vlan);
-	if (!vlan)
-		return -ENOMEM;
+	if (!vlan) {
+		ret = -ENOMEM;
+		goto out_unlock;
+	}
 
 	vlan->proto = proto;
 	vlan->vid = vid;
@@ -1709,45 +1720,60 @@ int ncsi_vlan_rx_add_vid(struct net_device *dev, __be16 proto, u16 vid)
 
 	found = ncsi_kick_channels(ndp) != 0;
 
-	return found ? ncsi_process_next_channel(ndp) : 0;
+	ret = found ? ncsi_process_next_channel(ndp) : 0;
+out_unlock:
+	mutex_unlock(&ncsi_dev_mutex);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(ncsi_vlan_rx_add_vid);
 
 int ncsi_vlan_rx_kill_vid(struct net_device *dev, __be16 proto, u16 vid)
 {
-	struct vlan_vid *vlan, *tmp;
+	struct vlan_vid *vlan;
 	struct ncsi_dev_priv *ndp;
 	struct ncsi_dev *nd;
 	bool found = false;
+	int ret;
 
 	if (vid == 0)
 		return 0;
 
+	mutex_lock(&ncsi_dev_mutex);
+	rcu_read_lock();
 	nd = ncsi_find_dev(dev);
+	rcu_read_unlock();
 	if (!nd) {
 		netdev_warn(dev, "NCSI: no net_device?\n");
-		return 0;
+		ret = 0;
+		goto out_unlock;
 	}
 
 	ndp = TO_NCSI_DEV_PRIV(nd);
 
 	/* Remove the VLAN id from our internal list */
-	list_for_each_entry_safe(vlan, tmp, &ndp->vlan_vids, list)
+	rcu_read_lock();
+	list_for_each_entry_rcu(vlan, &ndp->vlan_vids, list)
 		if (vlan->vid == vid) {
 			netdev_dbg(dev, "NCSI: vid %u found, removing\n", vid);
 			list_del_rcu(&vlan->list);
 			found = true;
-			kfree(vlan);
+			kfree_rcu(vlan, rcu);
+			break;
 		}
+	rcu_read_unlock();
 
 	if (!found) {
 		netdev_err(dev, "NCSI: vid %u wasn't registered!\n", vid);
-		return -EINVAL;
+		ret = -EINVAL;
+		goto out_unlock;
 	}
 
 	found = ncsi_kick_channels(ndp) != 0;
 
-	return found ? ncsi_process_next_channel(ndp) : 0;
+	ret = found ? ncsi_process_next_channel(ndp) : 0;
+out_unlock:
+	mutex_unlock(&ncsi_dev_mutex);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(ncsi_vlan_rx_kill_vid);
 
@@ -1762,14 +1788,21 @@ struct ncsi_dev *ncsi_register_dev(struct net_device *dev,
 	int i;
 
 	/* Check if the device has been registered or not */
+	mutex_lock(&ncsi_dev_mutex);
+	rcu_read_lock();
 	nd = ncsi_find_dev(dev);
-	if (nd)
+	rcu_read_unlock();
+	if (nd) {
+		mutex_unlock(&ncsi_dev_mutex);
 		return nd;
+	}
 
 	/* Create NCSI device */
 	ndp = kzalloc_obj(*ndp, GFP_ATOMIC);
-	if (!ndp)
+	if (!ndp) {
+		mutex_unlock(&ncsi_dev_mutex);
 		return NULL;
+	}
 
 	nd = &ndp->ndev;
 	nd->state = ncsi_dev_state_registered;
@@ -1810,6 +1843,7 @@ struct ncsi_dev *ncsi_register_dev(struct net_device *dev,
 			ndp->mlx_multi_host = true;
 	}
 
+	mutex_unlock(&ncsi_dev_mutex);
 	return nd;
 }
 EXPORT_SYMBOL_GPL(ncsi_register_dev);
@@ -1956,19 +1990,35 @@ void ncsi_unregister_dev(struct ncsi_dev *nd)
 {
 	struct ncsi_dev_priv *ndp = TO_NCSI_DEV_PRIV(nd);
 	struct ncsi_package *np, *tmp;
+	struct ncsi_channel *nc;
 	unsigned long flags;
+	int i;
 
-	dev_remove_pack(&ndp->ptype);
-
-	list_for_each_entry_safe(np, tmp, &ndp->packages, node)
-		ncsi_remove_package(np);
-
+	mutex_lock(&ncsi_dev_mutex);
 	spin_lock_irqsave(&ncsi_dev_lock, flags);
 	list_del_rcu(&ndp->node);
 	spin_unlock_irqrestore(&ncsi_dev_lock, flags);
+	mutex_unlock(&ncsi_dev_mutex);
 
+	dev_remove_pack(&ndp->ptype);
+
+	/* Wait for readers that found this device before it was unlinked. */
+	synchronize_rcu();
 	disable_work_sync(&ndp->work);
 
+	/* Stop all request producers before draining request state. */
+	list_for_each_entry(np, &ndp->packages, node) {
+		list_for_each_entry(nc, &np->channels, node)
+			ncsi_stop_channel_monitor(nc);
+	}
+
+	for (i = 0; i < ARRAY_SIZE(ndp->requests); i++) {
+		timer_delete_sync(&ndp->requests[i].timer);
+	}
+
+	list_for_each_entry_safe(np, tmp, &ndp->packages, node)
+		ncsi_remove_package(np);
+
 	kfree(ndp);
 }
 EXPORT_SYMBOL_GPL(ncsi_unregister_dev);
diff --git a/net/ncsi/ncsi-netlink.c b/net/ncsi/ncsi-netlink.c
index 8cc538358f6a..202d4547d31d 100644
--- a/net/ncsi/ncsi-netlink.c
+++ b/net/ncsi/ncsi-netlink.c
@@ -169,19 +169,24 @@ static int ncsi_pkg_info_nl(struct sk_buff *msg, struct genl_info *info)
 	if (!info->attrs[NCSI_ATTR_PACKAGE_ID])
 		return -EINVAL;
 
-	ndp = ndp_from_ifindex(genl_info_net(info),
-			       nla_get_u32(info->attrs[NCSI_ATTR_IFINDEX]));
-	if (!ndp)
-		return -ENODEV;
-
 	skb = genlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
 	if (!skb)
 		return -ENOMEM;
 
+	rcu_read_lock();
+	ndp = ndp_from_ifindex(genl_info_net(info),
+			       nla_get_u32(info->attrs[NCSI_ATTR_IFINDEX]));
+	if (!ndp) {
+		rcu_read_unlock();
+		kfree_skb(skb);
+		return -ENODEV;
+	}
+
 	hdr = genlmsg_put(skb, info->snd_portid, info->snd_seq,
 			  &ncsi_genl_family, 0, NCSI_CMD_PKG_INFO);
 	if (!hdr) {
 		kfree_skb(skb);
+		rcu_read_unlock();
 		return -EMSGSIZE;
 	}
 
@@ -190,6 +195,7 @@ static int ncsi_pkg_info_nl(struct sk_buff *msg, struct genl_info *info)
 	attr = nla_nest_start_noflag(skb, NCSI_ATTR_PACKAGE_LIST);
 	if (!attr) {
 		kfree_skb(skb);
+		rcu_read_unlock();
 		return -EMSGSIZE;
 	}
 	rc = ncsi_write_package_info(skb, ndp, package_id);
@@ -202,10 +208,12 @@ static int ncsi_pkg_info_nl(struct sk_buff *msg, struct genl_info *info)
 	nla_nest_end(skb, attr);
 
 	genlmsg_end(skb, hdr);
+	rcu_read_unlock();
 	return genlmsg_reply(skb, info);
 
 err:
 	kfree_skb(skb);
+	rcu_read_unlock();
 	return rc;
 }
 
@@ -228,11 +236,14 @@ static int ncsi_pkg_info_all_nl(struct sk_buff *skb,
 	if (!attrs[NCSI_ATTR_IFINDEX])
 		return -EINVAL;
 
-	ndp = ndp_from_ifindex(get_net(sock_net(skb->sk)),
+	rcu_read_lock();
+	ndp = ndp_from_ifindex(sock_net(skb->sk),
 			       nla_get_u32(attrs[NCSI_ATTR_IFINDEX]));
 
-	if (!ndp)
+	if (!ndp) {
+		rcu_read_unlock();
 		return -ENODEV;
+	}
 
 	package_id = cb->args[0];
 	package = NULL;
@@ -240,20 +251,23 @@ static int ncsi_pkg_info_all_nl(struct sk_buff *skb,
 		if (np->id == package_id)
 			package = np;
 
-	if (!package)
+	if (!package) {
+		rcu_read_unlock();
 		return 0; /* done */
+	}
 
 	hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq,
 			  &ncsi_genl_family, NLM_F_MULTI,  NCSI_CMD_PKG_INFO);
 	if (!hdr) {
-		rc = -EMSGSIZE;
-		goto err;
+		rcu_read_unlock();
+		return -EMSGSIZE;
 	}
 
 	attr = nla_nest_start_noflag(skb, NCSI_ATTR_PACKAGE_LIST);
 	if (!attr) {
-		rc = -EMSGSIZE;
-		goto err;
+		genlmsg_cancel(skb, hdr);
+		rcu_read_unlock();
+		return -EMSGSIZE;
 	}
 	rc = ncsi_write_package_info(skb, ndp, package->id);
 	if (rc) {
@@ -266,9 +280,12 @@ static int ncsi_pkg_info_all_nl(struct sk_buff *skb,
 
 	cb->args[0] = package_id + 1;
 
-	return skb->len;
+	rc = skb->len;
+	rcu_read_unlock();
+	return rc;
 err:
 	genlmsg_cancel(skb, hdr);
+	rcu_read_unlock();
 	return rc;
 }
 
@@ -289,10 +306,13 @@ static int ncsi_set_interface_nl(struct sk_buff *msg, struct genl_info *info)
 	if (!info->attrs[NCSI_ATTR_PACKAGE_ID])
 		return -EINVAL;
 
-	ndp = ndp_from_ifindex(get_net(sock_net(msg->sk)),
+	rcu_read_lock();
+	ndp = ndp_from_ifindex(sock_net(msg->sk),
 			       nla_get_u32(info->attrs[NCSI_ATTR_IFINDEX]));
-	if (!ndp)
+	if (!ndp) {
+		rcu_read_unlock();
 		return -ENODEV;
+	}
 
 	package_id = nla_get_u32(info->attrs[NCSI_ATTR_PACKAGE_ID]);
 	package = NULL;
@@ -302,6 +322,7 @@ static int ncsi_set_interface_nl(struct sk_buff *msg, struct genl_info *info)
 			package = np;
 	if (!package) {
 		/* The user has set a package that does not exist */
+		rcu_read_unlock();
 		return -ERANGE;
 	}
 
@@ -317,6 +338,7 @@ static int ncsi_set_interface_nl(struct sk_buff *msg, struct genl_info *info)
 			netdev_info(ndp->ndev.dev,
 				    "NCSI: Channel %u does not exist!\n",
 				    channel_id);
+			rcu_read_unlock();
 			return -ERANGE;
 		}
 	}
@@ -350,6 +372,7 @@ static int ncsi_set_interface_nl(struct sk_buff *msg, struct genl_info *info)
 	if (!(ndp->flags & NCSI_DEV_RESET))
 		ncsi_reset_dev(&ndp->ndev);
 
+	rcu_read_unlock();
 	return 0;
 }
 
@@ -365,10 +388,13 @@ static int ncsi_clear_interface_nl(struct sk_buff *msg, struct genl_info *info)
 	if (!info->attrs[NCSI_ATTR_IFINDEX])
 		return -EINVAL;
 
-	ndp = ndp_from_ifindex(get_net(sock_net(msg->sk)),
+	rcu_read_lock();
+	ndp = ndp_from_ifindex(sock_net(msg->sk),
 			       nla_get_u32(info->attrs[NCSI_ATTR_IFINDEX]));
-	if (!ndp)
+	if (!ndp) {
+		rcu_read_unlock();
 		return -ENODEV;
+	}
 
 	/* Reset any whitelists and disable multi mode */
 	spin_lock_irqsave(&ndp->lock, flags);
@@ -389,6 +415,7 @@ static int ncsi_clear_interface_nl(struct sk_buff *msg, struct genl_info *info)
 	if (!(ndp->flags & NCSI_DEV_RESET))
 		ncsi_reset_dev(&ndp->ndev);
 
+	rcu_read_unlock();
 	return 0;
 }
 
@@ -398,6 +425,7 @@ static int ncsi_send_cmd_nl(struct sk_buff *msg, struct genl_info *info)
 	struct ncsi_pkt_hdr *hdr;
 	struct ncsi_cmd_arg nca;
 	unsigned char *data;
+	bool rcu_locked = false;
 	u32 package_id;
 	u32 channel_id;
 	int len, ret;
@@ -427,10 +455,14 @@ static int ncsi_send_cmd_nl(struct sk_buff *msg, struct genl_info *info)
 		goto out;
 	}
 
-	ndp = ndp_from_ifindex(get_net(sock_net(msg->sk)),
+	rcu_read_lock();
+	rcu_locked = true;
+	ndp = ndp_from_ifindex(sock_net(msg->sk),
 			       nla_get_u32(info->attrs[NCSI_ATTR_IFINDEX]));
 	if (!ndp) {
 		ret = -ENODEV;
+		rcu_read_unlock();
+		rcu_locked = false;
 		goto out;
 	}
 
@@ -480,6 +512,8 @@ static int ncsi_send_cmd_nl(struct sk_buff *msg, struct genl_info *info)
 				      ret);
 	}
 out:
+	if (rcu_locked)
+		rcu_read_unlock();
 	return ret;
 }
 
@@ -608,10 +642,13 @@ static int ncsi_set_package_mask_nl(struct sk_buff *msg,
 	if (!info->attrs[NCSI_ATTR_PACKAGE_MASK])
 		return -EINVAL;
 
-	ndp = ndp_from_ifindex(get_net(sock_net(msg->sk)),
+	rcu_read_lock();
+	ndp = ndp_from_ifindex(sock_net(msg->sk),
 			       nla_get_u32(info->attrs[NCSI_ATTR_IFINDEX]));
-	if (!ndp)
+	if (!ndp) {
+		rcu_read_unlock();
 		return -ENODEV;
+	}
 
 	spin_lock_irqsave(&ndp->lock, flags);
 	if (nla_get_flag(info->attrs[NCSI_ATTR_MULTI_FLAG])) {
@@ -639,6 +676,7 @@ static int ncsi_set_package_mask_nl(struct sk_buff *msg,
 			ncsi_reset_dev(&ndp->ndev);
 	}
 
+	rcu_read_unlock();
 	return rc;
 }
 
@@ -663,10 +701,13 @@ static int ncsi_set_channel_mask_nl(struct sk_buff *msg,
 	if (!info->attrs[NCSI_ATTR_CHANNEL_MASK])
 		return -EINVAL;
 
-	ndp = ndp_from_ifindex(get_net(sock_net(msg->sk)),
+	rcu_read_lock();
+	ndp = ndp_from_ifindex(sock_net(msg->sk),
 			       nla_get_u32(info->attrs[NCSI_ATTR_IFINDEX]));
-	if (!ndp)
+	if (!ndp) {
+		rcu_read_unlock();
 		return -ENODEV;
+	}
 
 	package_id = nla_get_u32(info->attrs[NCSI_ATTR_PACKAGE_ID]);
 	package = NULL;
@@ -675,8 +716,10 @@ static int ncsi_set_channel_mask_nl(struct sk_buff *msg,
 			package = np;
 			break;
 		}
-	if (!package)
+	if (!package) {
+		rcu_read_unlock();
 		return -ERANGE;
+	}
 
 	spin_lock_irqsave(&package->lock, flags);
 
@@ -690,6 +733,7 @@ static int ncsi_set_channel_mask_nl(struct sk_buff *msg,
 			}
 		if (!channel) {
 			spin_unlock_irqrestore(&package->lock, flags);
+			rcu_read_unlock();
 			return -ERANGE;
 		}
 		netdev_dbg(ndp->ndev.dev,
@@ -721,6 +765,7 @@ static int ncsi_set_channel_mask_nl(struct sk_buff *msg,
 	if (!(ndp->flags & NCSI_DEV_RESET))
 		ncsi_reset_dev(&ndp->ndev);
 
+	rcu_read_unlock();
 	return 0;
 }
 

base-commit: a7bfaba4823e3c165bb2004c74eff7c096672bc7
-- 
2.55.0