sock_diag: allow to dump bpf filters

This patch allows to dump BPF filters attached to a socket with
SO_ATTACH_FILTER.
Note that we check CAP_SYS_ADMIN before allowing to dump this info.

For now, only AF_PACKET sockets use this feature.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 33 insertions, 0 deletions

diff --git a/net/core/sock_diag.c b/net/core/sock_diag.c
index a29e90cf36b..d5bef0b0f63 100644
--- a/net/core/sock_diag.c
+++ b/net/core/sock_diag.c
@@ -49,6 +49,39 @@ int sock_diag_put_meminfo(struct sock *sk, struct sk_buff *skb, int attrtype)
 }
 EXPORT_SYMBOL_GPL(sock_diag_put_meminfo);
 
+int sock_diag_put_filterinfo(struct user_namespace *user_ns, struct sock *sk,
+			     struct sk_buff *skb, int attrtype)
+{
+	struct nlattr *attr;
+	struct sk_filter *filter;
+	unsigned int len;
+	int err = 0;
+
+	if (!ns_capable(user_ns, CAP_NET_ADMIN)) {
+		nla_reserve(skb, attrtype, 0);
+		return 0;
+	}
+
+	rcu_read_lock();
+
+	filter = rcu_dereference(sk->sk_filter);
+	len = filter ? filter->len * sizeof(struct sock_filter) : 0;
+
+	attr = nla_reserve(skb, attrtype, len);
+	if (attr == NULL) {
+		err = -EMSGSIZE;
+		goto out;
+	}
+
+	if (filter)
+		memcpy(nla_data(attr), filter->insns, len);
+
+out:
+	rcu_read_unlock();
+	return err;
+}
+EXPORT_SYMBOL(sock_diag_put_filterinfo);
+
 void sock_diag_register_inet_compat(int (*fn)(struct sk_buff *skb, struct nlmsghdr *nlh))
 {
 	mutex_lock(&sock_diag_table_mutex);