[PATCH net] ipv4: ip_tunnel: spread netdev_lockdep_set_classes()

[Eric Dumazet <edumazet@google.com>]

Inspired by yet another syzbot report.

IPv6 tunnels call netdev_lockdep_set_classes() for each tunnel type,
while IPv4 currently centralizes netdev_lockdep_set_classes() call from
ip_tunnel_init().

Make ip_tunnel_init() a macro, so that we have different lockdep
classes per tunnel type.

Fixes: 0bef512012b1 ("net: add netdev_lockdep_set_classes() to virtual drivers")
Reported-by: syzbot+1240b33467289f5ab50b@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/695d439f.050a0220.1c677c.0347.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/ip_tunnels.h | 13 ++++++++++++-
 net/ipv4/ip_tunnel.c     |  5 ++---
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h
index ecae35512b9b449fa061d96e66eb4533d1816bef..4021e6a73e32b80145d9241e4aca5e7881f04c30 100644
--- a/include/net/ip_tunnels.h
+++ b/include/net/ip_tunnels.h
@@ -19,6 +19,7 @@
 #include <net/rtnetlink.h>
 #include <net/lwtunnel.h>
 #include <net/dst_cache.h>
+#include <net/netdev_lock.h>
 
 #if IS_ENABLED(CONFIG_IPV6)
 #include <net/ipv6.h>
@@ -372,7 +373,17 @@ static inline void ip_tunnel_init_flow(struct flowi4 *fl4,
 	fl4->flowi4_flags = flow_flags;
 }
 
-int ip_tunnel_init(struct net_device *dev);
+int __ip_tunnel_init(struct net_device *dev);
+#define ip_tunnel_init(DEV)			\
+({						\
+	struct net_device *__dev = (DEV);	\
+	int __res = __ip_tunnel_init(__dev);	\
+						\
+	if (!__res)				\
+		netdev_lockdep_set_classes(__dev);\
+	__res;					\
+})
+
 void ip_tunnel_uninit(struct net_device *dev);
 void  ip_tunnel_dellink(struct net_device *dev, struct list_head *head);
 struct net *ip_tunnel_get_link_net(const struct net_device *dev);
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 158a30ae7c5f2f1fa39eea7c3d64e36fb5f7551a..50d0f5fe4e4c6d83ef18cdea3ca25aed582839f0 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -1281,7 +1281,7 @@ int ip_tunnel_changelink(struct net_device *dev, struct nlattr *tb[],
 }
 EXPORT_SYMBOL_GPL(ip_tunnel_changelink);
 
-int ip_tunnel_init(struct net_device *dev)
+int __ip_tunnel_init(struct net_device *dev)
 {
 	struct ip_tunnel *tunnel = netdev_priv(dev);
 	struct iphdr *iph = &tunnel->parms.iph;
@@ -1308,10 +1308,9 @@ int ip_tunnel_init(struct net_device *dev)
 
 	if (tunnel->collect_md)
 		netif_keep_dst(dev);
-	netdev_lockdep_set_classes(dev);
 	return 0;
 }
-EXPORT_SYMBOL_GPL(ip_tunnel_init);
+EXPORT_SYMBOL_GPL(__ip_tunnel_init);
 
 void ip_tunnel_uninit(struct net_device *dev)
 {
-- 
2.52.0.351.gbe84eed79e-goog