[PATCH v2 net] dpll: rely on rcu for netdev_dpll_pin()

[Eric Dumazet <edumazet@google.com>]

This fixes a possible UAF in if_nlmsg_size(),
which can run without RTNL.

Add rcu protection to "struct dpll_pin"

Move netdev_dpll_pin() from netdevice.h to dpll.h to
decrease name pollution.

Note: This looks possible to no longer acquire RTNL in
netdev_dpll_pin_assign() later in net-next.

v2: do not force rcu_read_lock() in rtnl_dpll_pin_size() (Jiri Pirko)

Fixes: 5f1842692880 ("netdev: expose DPLL pin handle for netdevice")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jiri Pirko <jiri@nvidia.com>
Cc: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Cc: Vadim Fedorenko <vadim.fedorenko@linux.dev>
---
 drivers/dpll/dpll_core.c  |  2 +-
 drivers/dpll/dpll_core.h  |  2 ++
 include/linux/dpll.h      | 11 +++++++++++
 include/linux/netdevice.h | 11 +----------
 net/core/dev.c            |  2 +-
 5 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/drivers/dpll/dpll_core.c b/drivers/dpll/dpll_core.c
index 5152bd1b0daf599869195e81805fbb2709dbe6b4..4c2bb27c99fe4e517b0d92c4ae3db83a679c7d11 100644
--- a/drivers/dpll/dpll_core.c
+++ b/drivers/dpll/dpll_core.c
@@ -564,7 +564,7 @@ void dpll_pin_put(struct dpll_pin *pin)
 		xa_destroy(&pin->parent_refs);
 		xa_erase(&dpll_pin_xa, pin->id);
 		dpll_pin_prop_free(&pin->prop);
-		kfree(pin);
+		kfree_rcu(pin, rcu);
 	}
 	mutex_unlock(&dpll_lock);
 }
diff --git a/drivers/dpll/dpll_core.h b/drivers/dpll/dpll_core.h
index 717f715015c742238d5585fddc5cd267fbb0db9f..2b6d8ef1cdf36cff24328e497c49d667659dd0e6 100644
--- a/drivers/dpll/dpll_core.h
+++ b/drivers/dpll/dpll_core.h
@@ -47,6 +47,7 @@ struct dpll_device {
  * @prop:		pin properties copied from the registerer
  * @rclk_dev_name:	holds name of device when pin can recover clock from it
  * @refcount:		refcount
+ * @rcu:		rcu_head for kfree_rcu()
  **/
 struct dpll_pin {
 	u32 id;
@@ -57,6 +58,7 @@ struct dpll_pin {
 	struct xarray parent_refs;
 	struct dpll_pin_properties prop;
 	refcount_t refcount;
+	struct rcu_head rcu;
 };
 
 /**
diff --git a/include/linux/dpll.h b/include/linux/dpll.h
index 9cf896ea1d4122f3bc7094e46a5af81b999937dc..4ec2fe9caf5a3f284afd0cfe4fc7c2bf42cbbc60 100644
--- a/include/linux/dpll.h
+++ b/include/linux/dpll.h
@@ -10,6 +10,8 @@
 #include <uapi/linux/dpll.h>
 #include <linux/device.h>
 #include <linux/netlink.h>
+#include <linux/netdevice.h>
+#include <linux/rtnetlink.h>
 
 struct dpll_device;
 struct dpll_pin;
@@ -167,4 +169,13 @@ int dpll_device_change_ntf(struct dpll_device *dpll);
 
 int dpll_pin_change_ntf(struct dpll_pin *pin);
 
+static inline struct dpll_pin *netdev_dpll_pin(const struct net_device *dev)
+{
+#if IS_ENABLED(CONFIG_DPLL)
+	return rcu_dereference_rtnl(dev->dpll_pin);
+#else
+	return NULL;
+#endif
+}
+
 #endif
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index ef7bfbb9849733fa7f1f097ba53a36a68cc3384b..a9c973b92294bb110cf3cd336485972127b01b58 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2469,7 +2469,7 @@ struct net_device {
 	struct devlink_port	*devlink_port;
 
 #if IS_ENABLED(CONFIG_DPLL)
-	struct dpll_pin		*dpll_pin;
+	struct dpll_pin	__rcu	*dpll_pin;
 #endif
 #if IS_ENABLED(CONFIG_PAGE_POOL)
 	/** @page_pools: page pools created for this netdevice */
@@ -4035,15 +4035,6 @@ bool netdev_port_same_parent_id(struct net_device *a, struct net_device *b);
 void netdev_dpll_pin_set(struct net_device *dev, struct dpll_pin *dpll_pin);
 void netdev_dpll_pin_clear(struct net_device *dev);
 
-static inline struct dpll_pin *netdev_dpll_pin(const struct net_device *dev)
-{
-#if IS_ENABLED(CONFIG_DPLL)
-	return dev->dpll_pin;
-#else
-	return NULL;
-#endif
-}
-
 struct sk_buff *validate_xmit_skb_list(struct sk_buff *skb, struct net_device *dev, bool *again);
 struct sk_buff *dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
 				    struct netdev_queue *txq, int *ret);
diff --git a/net/core/dev.c b/net/core/dev.c
index 73a0219730075e666c4f11f668a50dbf9f9afa97..0230391c78f71e22d3c0e925ff8d3d792aa54a32 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -9078,7 +9078,7 @@ static void netdev_dpll_pin_assign(struct net_device *dev, struct dpll_pin *dpll
 {
 #if IS_ENABLED(CONFIG_DPLL)
 	rtnl_lock();
-	dev->dpll_pin = dpll_pin;
+	rcu_assign_pointer(dev->dpll_pin, dpll_pin);
 	rtnl_unlock();
 #endif
 }
-- 
2.44.0.rc1.240.g4c46232300-goog