[systemd-devel] [PATCH] netns: unix: only allow to find out unix socket in same net namespace

[Gao feng]

Unix sockets are private resources of net namespace,
allowing one net namespace to access to other netns's unix
sockets is meaningless.

I'm researching a problem about shutdown from container,
if the cotainer shares the same file /run/systemd/private
with host, when we run shutdown -h xxx in container, the
shutdown message will be send to the systemd-shutdownd
through unix socket /run/systemd/private, and because
systemd-shutdownd is running in host, so finally, the host
will become shutdown.

We should make sure unix sockets are per net namespace to
avoid this problem.

Signed-off-by: Gao feng <gaofeng at cn.fujitsu.com>
---
 net/unix/af_unix.c |  8 ++++++--
 net/unix/diag.c    | 11 ++++++++---
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index c4ce243..98e3689 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -295,7 +295,8 @@ static inline struct sock *unix_find_socket_byname(struct net *net,
 	return s;
 }
 
-static struct sock *unix_find_socket_byinode(struct inode *i)
+static struct sock *unix_find_socket_byinode(struct net *net,
+					     struct inode *i)
 {
 	struct sock *s;
 
@@ -304,6 +305,9 @@ static struct sock *unix_find_socket_byinode(struct inode *i)
 		    &unix_socket_table[i->i_ino & (UNIX_HASH_SIZE - 1)]) {
 		struct dentry *dentry = unix_sk(s)->path.dentry;
 
+		if (!net_eq(sock_net(s), net))
+			continue;
+
 		if (dentry && dentry->d_inode == i) {
 			sock_hold(s);
 			goto found;
@@ -784,7 +788,7 @@ static struct sock *unix_find_other(struct net *net,
 		err = -ECONNREFUSED;
 		if (!S_ISSOCK(inode->i_mode))
 			goto put_fail;
-		u = unix_find_socket_byinode(inode);
+		u = unix_find_socket_byinode(net, inode);
 		if (!u)
 			goto put_fail;
 
diff --git a/net/unix/diag.c b/net/unix/diag.c
index d591091..80ada12 100644
--- a/net/unix/diag.c
+++ b/net/unix/diag.c
@@ -218,20 +218,25 @@ done:
 	return skb->len;
 }
 
-static struct sock *unix_lookup_by_ino(int ino)
+static struct sock *unix_lookup_by_ino(struct net *net, int ino)
 {
 	int i;
 	struct sock *sk;
 
 	spin_lock(&unix_table_lock);
 	for (i = 0; i < ARRAY_SIZE(unix_socket_table); i++) {
-		sk_for_each(sk, &unix_socket_table[i])
+		sk_for_each(sk, &unix_socket_table[i]) {
+
+			if (!net_eq(sock_net(sk), net))
+				continue;
+
 			if (ino == sock_i_ino(sk)) {
 				sock_hold(sk);
 				spin_unlock(&unix_table_lock);
 
 				return sk;
 			}
+		}
 	}
 
 	spin_unlock(&unix_table_lock);
@@ -251,7 +256,7 @@ static int unix_diag_get_exact(struct sk_buff *in_skb,
 	if (req->udiag_ino == 0)
 		goto out_nosk;
 
-	sk = unix_lookup_by_ino(req->udiag_ino);
+	sk = unix_lookup_by_ino(net, req->udiag_ino);
 	err = -ENOENT;
 	if (sk == NULL)
 		goto out_nosk;
-- 
1.8.3.1