Re: [syzbot] [net?] KASAN: slab-out-of-bounds Read in dsa_user_prechangeupper

[Edward Adam Davis <eadavis@qq.com>]

please test slab-out-of-bounds Read in dsa_user_prechangeupper

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 3e7aeb78ab01

diff --git a/net/dsa/user.h b/net/dsa/user.h
index 996069130bea..9a40918ee7fc 100644
--- a/net/dsa/user.h
+++ b/net/dsa/user.h
@@ -53,7 +53,11 @@ int dsa_user_manage_vlan_filtering(struct net_device *dev,
 
 static inline struct dsa_port *dsa_user_to_port(const struct net_device *dev)
 {
-	struct dsa_user_priv *p = netdev_priv(dev);
+	const struct rtnl_link_ops *ops = dev->rtnl_link_ops;
+	struct dsa_user_priv *p = ops->priv_size >= sizeof(*p) ? 
+		netdev_priv(dev) : NULL;
+	if (!p)
+		return NULL;
 
 	return p->dp;
 }