flow_dissector: Pull BPF program assignment up to bpf-netns

Prepare for using bpf_prog_array to store attached programs by moving out
code that updates the attached program out of flow dissector.

Managing bpf_prog_array is more involved than updating a single bpf_prog
pointer. This will let us do it all from one place, bpf/net_namespace.c, in
the subsequent patch.

No functional change intended.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200625141357.910330-2-jakub@cloudflare.com

diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
index a7eba43..4b6e362 100644 (file)
--- a/include/net/flow_dissector.h
+++ b/include/net/flow_dissector.h
@@ -372,7 +372,8 @@ flow_dissector_init_keys(struct flow_dissector_key_control *key_control,
 }
 
 #ifdef CONFIG_BPF_SYSCALL
-int flow_dissector_bpf_prog_attach(struct net *net, struct bpf_prog *prog);
+int flow_dissector_bpf_prog_attach_check(struct net *net,
+                                        struct bpf_prog *prog);
 #endif /* CONFIG_BPF_SYSCALL */
 
 #endif

diff --git a/kernel/bpf/net_namespace.c b/kernel/bpf/net_namespace.c
index 78cf061..b951dab 100644 (file)
--- a/kernel/bpf/net_namespace.c
+++ b/kernel/bpf/net_namespace.c
@@ -189,6 +189,7 @@ int netns_bpf_prog_query(const union bpf_attr *attr,
 int netns_bpf_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
 {
        enum netns_bpf_attach_type type;
+       struct bpf_prog *attached;
        struct net *net;
        int ret;
 
@@ -207,12 +208,26 @@ int netns_bpf_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
 
        switch (type) {
        case NETNS_BPF_FLOW_DISSECTOR:
-               ret = flow_dissector_bpf_prog_attach(net, prog);
+               ret = flow_dissector_bpf_prog_attach_check(net, prog);
                break;
        default:
                ret = -EINVAL;
                break;
        }
+       if (ret)
+               goto out_unlock;
+
+       attached = rcu_dereference_protected(net->bpf.progs[type],
+                                            lockdep_is_held(&netns_bpf_mutex));
+       if (attached == prog) {
+               /* The same program cannot be attached twice */
+               ret = -EINVAL;
+               goto out_unlock;
+       }
+       rcu_assign_pointer(net->bpf.progs[type], prog);
+       if (attached)
+               bpf_prog_put(attached);
+
 out_unlock:
        mutex_unlock(&netns_bpf_mutex);
 
@@ -277,7 +292,7 @@ static int netns_bpf_link_attach(struct net *net, struct bpf_link *link,
 
        switch (type) {
        case NETNS_BPF_FLOW_DISSECTOR:
-               err = flow_dissector_bpf_prog_attach(net, link->prog);
+               err = flow_dissector_bpf_prog_attach_check(net, link->prog);
                break;
        default:
                err = -EINVAL;
@@ -286,6 +301,7 @@ static int netns_bpf_link_attach(struct net *net, struct bpf_link *link,
        if (err)
                goto out_unlock;
 
+       rcu_assign_pointer(net->bpf.progs[type], link->prog);
        net->bpf.links[type] = link;
 
 out_unlock:

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index d02df0b..b57fb13 100644 (file)
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -70,10 +70,10 @@ void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
 EXPORT_SYMBOL(skb_flow_dissector_init);
 
 #ifdef CONFIG_BPF_SYSCALL
-int flow_dissector_bpf_prog_attach(struct net *net, struct bpf_prog *prog)
+int flow_dissector_bpf_prog_attach_check(struct net *net,
+                                        struct bpf_prog *prog)
 {
        enum netns_bpf_attach_type type = NETNS_BPF_FLOW_DISSECTOR;
-       struct bpf_prog *attached;
 
        if (net == &init_net) {
                /* BPF flow dissector in the root namespace overrides
@@ -97,15 +97,6 @@ int flow_dissector_bpf_prog_attach(struct net *net, struct bpf_prog *prog)
                        return -EEXIST;
        }
 
-       attached = rcu_dereference_protected(net->bpf.progs[type],
-                                            lockdep_is_held(&netns_bpf_mutex));
-       if (attached == prog)
-               /* The same program cannot be attached twice */
-               return -EINVAL;
-
-       rcu_assign_pointer(net->bpf.progs[type], prog);
-       if (attached)
-               bpf_prog_put(attached);
        return 0;
 }
 #endif /* CONFIG_BPF_SYSCALL */