diff mbox series

[bpf-next,1/2] bpf: support BPF_PROG_QUERY for BPF_FLOW_DISSECTOR attach_type

Message ID 20190423232200.101627-1-sdf@google.com
State Changes Requested
Delegated to: BPF Maintainers
Headers show
Series [bpf-next,1/2] bpf: support BPF_PROG_QUERY for BPF_FLOW_DISSECTOR attach_type | expand

Commit Message

Stanislav Fomichev April 23, 2019, 11:21 p.m. UTC 
target_fd is target namespace. If there is a flow dissector BPF program
attached to that namespace, its (single) id is returned.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
---
 include/linux/skbuff.h    |  8 ++++++++
 kernel/bpf/syscall.c      |  2 ++
 net/core/flow_dissector.c | 36 ++++++++++++++++++++++++++++++++++++
 3 files changed, 46 insertions(+)

Comments

Jakub Kicinski April 23, 2019, 11:28 p.m. UTC | #1 
On Tue, 23 Apr 2019 16:21:59 -0700, Stanislav Fomichev wrote:
> +	rcu_read_lock();
> +	attached = rcu_dereference(net->flow_dissector_prog);
> +	if (attached) {
> +		cnt = 1;
> +		if (prog_ids &&
> +		    copy_to_user(prog_ids, &attached->aux->id, sizeof(u32))) {

Not sure you can do copy_to_user inside an RCU section, doesn't it
sleep?

> +			rcu_read_unlock();
> +			return -EFAULT;
> +		}
> +	}
> +	rcu_read_unlock();
Stanislav Fomichev April 24, 2019, 12:12 a.m. UTC | #2 
On 04/23, Jakub Kicinski wrote:
> On Tue, 23 Apr 2019 16:21:59 -0700, Stanislav Fomichev wrote:
> > +	rcu_read_lock();
> > +	attached = rcu_dereference(net->flow_dissector_prog);
> > +	if (attached) {
> > +		cnt = 1;
> > +		if (prog_ids &&
> > +		    copy_to_user(prog_ids, &attached->aux->id, sizeof(u32))) {
> 
> Not sure you can do copy_to_user inside an RCU section, doesn't it
> sleep?
Good point, I need to copy that aux->id somewhere and exit rcu section.

> > +			rcu_read_unlock();
> > +			return -EFAULT;
> > +		}
> > +	}
> > +	rcu_read_unlock();
>
diff mbox series

Patch

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 998256c2820b..9f499c0ac53b 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1258,11 +1258,19 @@  void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
 			     unsigned int key_count);
 
 #ifdef CONFIG_NET
+int skb_flow_dissector_prog_query(const union bpf_attr *attr,
+				  union bpf_attr __user *uattr);
 int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr,
 				       struct bpf_prog *prog);
 
 int skb_flow_dissector_bpf_prog_detach(const union bpf_attr *attr);
 #else
+static int skb_flow_dissector_prog_query(const union bpf_attr *attr,
+					 union bpf_attr __user *uattr)
+{
+	return -EOPNOTSUPP;
+}
+
 static inline int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr,
 						     struct bpf_prog *prog)
 {
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 92c9b8a32b50..b0de49598341 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2009,6 +2009,8 @@  static int bpf_prog_query(const union bpf_attr *attr,
 		break;
 	case BPF_LIRC_MODE2:
 		return lirc_prog_query(attr, uattr);
+	case BPF_FLOW_DISSECTOR:
+		return skb_flow_dissector_prog_query(attr, uattr);
 	default:
 		return -EINVAL;
 	}
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index fac712cee9d5..d3c41cb7dbb8 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -65,6 +65,42 @@  void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
 }
 EXPORT_SYMBOL(skb_flow_dissector_init);
 
+int skb_flow_dissector_prog_query(const union bpf_attr *attr,
+				  union bpf_attr __user *uattr)
+{
+	__u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
+	struct bpf_prog *attached;
+	u32 cnt = 0, flags = 0;
+	struct net *net;
+
+	if (attr->query.query_flags)
+		return -EINVAL;
+
+	net = get_net_ns_by_fd(attr->query.target_fd);
+	if (IS_ERR(net))
+		return PTR_ERR(net);
+
+	rcu_read_lock();
+	attached = rcu_dereference(net->flow_dissector_prog);
+	if (attached) {
+		cnt = 1;
+		if (prog_ids &&
+		    copy_to_user(prog_ids, &attached->aux->id, sizeof(u32))) {
+			rcu_read_unlock();
+			return -EFAULT;
+		}
+	}
+	rcu_read_unlock();
+
+	if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)))
+		return -EFAULT;
+
+	if (copy_to_user(&uattr->query.prog_cnt, &cnt, sizeof(cnt)))
+		return -EFAULT;
+
+	return 0;
+}
+
 int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr,
 				       struct bpf_prog *prog)
 {