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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: d58e468b11 ("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>
This commit is contained in:
Willem de Bruijn 2018-09-24 16:49:57 -04:00 committed by Daniel Borkmann
parent 7ea3c40605
commit d0e13a1488
1 changed files with 9 additions and 3 deletions
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12
net/core/flow_dissector.c
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@ -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