From: Willem de Bruijn <willemb@google.com>
Date: Mon, 24 Sep 2018 20:49:57 +0000 (-0400)
Subject: flow_dissector: lookup netns by skb->sk if skb->dev is NULL
X-Git-Tag: baikal/mips/sdk5.9~17461^2~258^2
X-Git-Url: https://git.baikalelectronics.ru/sdk/?a=commitdiff_plain;h=f83d422c274febcb0b30d6f8cc279af9dcdb88b1;p=kernel.git

flow_dissector: lookup netns by skb->sk if skb->dev is NULL

BPF flow dissectors are configured per network namespace.
__skb_flow_dissect looks up the netns through dev_net(skb->dev).

In some dissector paths skb->dev is NULL, such as for Unix sockets.
In these cases fall back to looking up the netns by socket.

Analyzing the codepaths leading to __skb_flow_dissect I did not find
a case where both skb->dev and skb->sk are NULL. Warn and fall back to
standard flow dissector if one is found.

Fixes: 23513a901445 ("flow_dissector: implements flow dissector BPF hook")
Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 5c5dd74b5b3b0..738c7562e1e07 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -714,7 +714,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 	struct flow_dissector_key_vlan *key_vlan;
 	enum flow_dissect_ret fdret;
 	enum flow_dissector_key_id dissector_vlan = FLOW_DISSECTOR_KEY_MAX;
-	struct bpf_prog *attached;
+	struct bpf_prog *attached = NULL;
 	int num_hdrs = 0;
 	u8 ip_proto = 0;
 	bool ret;
@@ -755,8 +755,14 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 					      target_container);
 
 	rcu_read_lock();
-	attached = skb ? rcu_dereference(dev_net(skb->dev)->flow_dissector_prog)
-		       : NULL;
+	if (skb) {
+		if (skb->dev)
+			attached = rcu_dereference(dev_net(skb->dev)->flow_dissector_prog);
+		else if (skb->sk)
+			attached = rcu_dereference(sock_net(skb->sk)->flow_dissector_prog);
+		else
+			WARN_ON_ONCE(1);
+	}
 	if (attached) {
 		/* Note that even though the const qualifier is discarded
 		 * throughout the execution of the BPF program, all changes(the