[PATCH net-next] ipv6: remove extra dev_hold() for fallback tunnels

[PATCH net-next] ipv6: remove extra dev_hold() for fallback tunnels

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

My previous commits added a dev_hold() in tunnels ndo_init(),
but forgot to remove it from special functions setting up fallback tunnels.

Fallback tunnels do call their respective ndo_init()

This leads to various reports like :

unregister_netdevice: waiting for ip6gre0 to become free. Usage count = 2

Fixes: 48bb5697269a ("ip6_tunnel: sit: proper dev_{hold|put} in ndo_[un]init methods")
Fixes: 6289a98f0817 ("sit: proper dev_{hold|put} in ndo_[un]init methods")
Fixes: 40cb881b5aaa ("ip6_vti: proper dev_{hold|put} in ndo_[un]init methods")
Fixes: 7f700334be9a ("ip6_gre: proper dev_{hold|put} in ndo_[un]init methods")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
---
 net/ipv6/ip6_gre.c    | 3 ---
 net/ipv6/ip6_tunnel.c | 1 -
 net/ipv6/ip6_vti.c    | 1 -
 net/ipv6/sit.c        | 1 -
 4 files changed, 6 deletions(-)

diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 9689bf9f46f347562330a4d8630c0b0b13a411fc..bc224f917bbd53beb9b8af5bdef3fb9794b8ee44 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -387,7 +387,6 @@ static struct ip6_tnl *ip6gre_tunnel_locate(struct net *net,
 	if (!(nt->parms.o_flags & TUNNEL_SEQ))
 		dev->features |= NETIF_F_LLTX;
 
-	dev_hold(dev);
 	ip6gre_tunnel_link(ign, nt);
 	return nt;
 
@@ -1539,8 +1538,6 @@ static void ip6gre_fb_tunnel_init(struct net_device *dev)
 	strcpy(tunnel->parms.name, dev->name);
 
 	tunnel->hlen		= sizeof(struct ipv6hdr) + 4;
-
-	dev_hold(dev);
 }
 
 static struct inet6_protocol ip6gre_protocol __read_mostly = {
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 67ee9d58ec5efcc81e8b27406bd4f57a0caea70b..07a0a06a9b52bc9974e2f36b1477c341c952f94a 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1925,7 +1925,6 @@ static int __net_init ip6_fb_tnl_dev_init(struct net_device *dev)
 	struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);
 
 	t->parms.proto = IPPROTO_IPV6;
-	dev_hold(dev);
 
 	rcu_assign_pointer(ip6n->tnls_wc[0], t);
 	return 0;
diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
index a018afdb3e062c9e664d4ca424176a859f0a332c..856e46ad0895b47b58896852afee3d4a398b139e 100644
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -963,7 +963,6 @@ static int __net_init vti6_fb_tnl_dev_init(struct net_device *dev)
 	struct vti6_net *ip6n = net_generic(net, vti6_net_id);
 
 	t->parms.proto = IPPROTO_IPV6;
-	dev_hold(dev);
 
 	rcu_assign_pointer(ip6n->tnls_wc[0], t);
 	return 0;
diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 488d3181aec3a5558dbefb6145400627535df761..ff2ca2e7c7f5045663069ea572560d58abee2970 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -1470,7 +1470,6 @@ static void __net_init ipip6_fb_tunnel_init(struct net_device *dev)
 	iph->ihl		= 5;
 	iph->ttl		= 64;
 
-	dev_hold(dev);
 	rcu_assign_pointer(sitn->tunnels_wc[0], tunnel);
 }
 
-- 
2.31.0.291.g576ba9dcdaf-goog

Re: [PATCH net-next] ipv6: remove extra dev_hold() for fallback tunnels

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Wed, 31 Mar 2021 14:38:11 -0700 you wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> My previous commits added a dev_hold() in tunnels ndo_init(),
> but forgot to remove it from special functions setting up fallback tunnels.
> 
> Fallback tunnels do call their respective ndo_init()
> 
> [...]

Here is the summary with links:
  - [net-next] ipv6: remove extra dev_hold() for fallback tunnels
    https://git.kernel.org/netdev/net-next/c/0d7a7b2014b1

You are awesome, thank you!
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