netdev - [PATCH net-next v4 3/3] sock_diag: allow to dump bpf filters

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Message-Id: <1366908834-21606-4-git-send-email-nicolas.dichtel@6wind.com>
Date:	Thu, 25 Apr 2013 18:53:54 +0200
From:	Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:	eric.dumazet@...il.com
Cc:	davem@...emloft.net, xiyou.wangcong@...il.com,
	netdev@...r.kernel.org, Nicolas Dichtel <nicolas.dichtel@...nd.com>
Subject: [PATCH net-next v4 3/3] 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@...nd.com>
---
 include/linux/sock_diag.h        |  3 +++
 include/uapi/linux/packet_diag.h |  2 ++
 net/core/sock_diag.c             | 33 +++++++++++++++++++++++++++++++++
 net/packet/diag.c                |  4 ++++
 4 files changed, 42 insertions(+)

diff --git a/include/linux/sock_diag.h b/include/linux/sock_diag.h
index e8d702e..54f91d3 100644
--- a/include/linux/sock_diag.h
+++ b/include/linux/sock_diag.h
@@ -1,6 +1,7 @@
 #ifndef __SOCK_DIAG_H__
 #define __SOCK_DIAG_H__
 
+#include <linux/user_namespace.h>
 #include <uapi/linux/sock_diag.h>
 
 struct sk_buff;
@@ -22,5 +23,7 @@ int sock_diag_check_cookie(void *sk, __u32 *cookie);
 void sock_diag_save_cookie(void *sk, __u32 *cookie);
 
 int sock_diag_put_meminfo(struct sock *sk, struct sk_buff *skb, int attr);
+int sock_diag_put_filterinfo(struct user_namespace *user_ns, struct sock *sk,
+			     struct sk_buff *skb, int attrtype);
 
 #endif
diff --git a/include/uapi/linux/packet_diag.h b/include/uapi/linux/packet_diag.h
index c0802c1..b2cc0cd 100644
--- a/include/uapi/linux/packet_diag.h
+++ b/include/uapi/linux/packet_diag.h
@@ -17,6 +17,7 @@ struct packet_diag_req {
 #define PACKET_SHOW_RING_CFG	0x00000004 /* Rings configuration parameters */
 #define PACKET_SHOW_FANOUT	0x00000008
 #define PACKET_SHOW_MEMINFO	0x00000010
+#define PACKET_SHOW_FILTER	0x00000020
 
 struct packet_diag_msg {
 	__u8	pdiag_family;
@@ -35,6 +36,7 @@ enum {
 	PACKET_DIAG_FANOUT,
 	PACKET_DIAG_UID,
 	PACKET_DIAG_MEMINFO,
+	PACKET_DIAG_FILTER,
 
 	__PACKET_DIAG_MAX,
 };
diff --git a/net/core/sock_diag.c b/net/core/sock_diag.c
index a29e90c..d5bef0b0 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);
diff --git a/net/packet/diag.c b/net/packet/diag.c
index 822fe9b..a9584a2 100644
--- a/net/packet/diag.c
+++ b/net/packet/diag.c
@@ -170,6 +170,10 @@ static int sk_diag_fill(struct sock *sk, struct sk_buff *skb,
 	    sock_diag_put_meminfo(sk, skb, PACKET_DIAG_MEMINFO))
 		goto out_nlmsg_trim;
 
+	if ((req->pdiag_show & PACKET_SHOW_FILTER) &&
+	    sock_diag_put_filterinfo(user_ns, sk, skb, PACKET_DIAG_FILTER))
+		goto out_nlmsg_trim;
+
 	return nlmsg_end(skb, nlh);
 
 out_nlmsg_trim:
-- 
1.8.2.1

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