[NETNS]: Namespace stop vs 'ip r l' race.
During network namespace stop process kernel side netlink sockets
belonging to a namespace should be closed. They should not prevent
namespace to stop, so they do not increment namespace usage
counter. Though this counter will be put during last sock_put.
The raplacement of the correct netns for init_ns solves the problem
only partial as socket to be stoped until proper stop is a valid
netlink kernel socket and can be looked up by the user processes. This
is not a problem until it resides in initial namespace (no processes
inside this net), but this is not true for init_net.
So, hold the referrence for a socket, remove it from lookup tables and
only after that change namespace and perform a last put.
Signed-off-by: Denis V. Lunev <den@openvz.org>
Tested-by: Alexey Dobriyan <adobriyan@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 02cf848..ddbdde8 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1368,25 +1368,14 @@
rtnetlink_rcv, &rtnl_mutex, THIS_MODULE);
if (!sk)
return -ENOMEM;
-
- /* Don't hold an extra reference on the namespace */
- put_net(sk->sk_net);
net->rtnl = sk;
return 0;
}
static void rtnetlink_net_exit(struct net *net)
{
- struct sock *sk = net->rtnl;
- if (sk) {
- /* At the last minute lie and say this is a socket for the
- * initial network namespace. So the socket will be safe to
- * free.
- */
- sk->sk_net = get_net(&init_net);
- netlink_kernel_release(net->rtnl);
- net->rtnl = NULL;
- }
+ netlink_kernel_release(net->rtnl);
+ net->rtnl = NULL;
}
static struct pernet_operations rtnetlink_net_ops = {
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index e787d21..62bd791 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -869,19 +869,14 @@
nl_fib_input, NULL, THIS_MODULE);
if (sk == NULL)
return -EAFNOSUPPORT;
- /* Don't hold an extra reference on the namespace */
- put_net(sk->sk_net);
net->ipv4.fibnl = sk;
return 0;
}
static void nl_fib_lookup_exit(struct net *net)
{
- /* At the last minute lie and say this is a socket for the
- * initial network namespace. So the socket will be safe to free.
- */
- net->ipv4.fibnl->sk_net = get_net(&init_net);
netlink_kernel_release(net->ipv4.fibnl);
+ net->ipv4.fibnl = NULL;
}
static void fib_disable_ip(struct net_device *dev, int force)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 626a582..6b178e1 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1396,6 +1396,9 @@
}
netlink_table_ungrab();
+ /* Do not hold an extra referrence to a namespace as this socket is
+ * internal to a namespace and does not prevent it to stop. */
+ put_net(net);
return sk;
out_sock_release:
@@ -1411,7 +1414,19 @@
{
if (sk == NULL || sk->sk_socket == NULL)
return;
+
+ /*
+ * Last sock_put should drop referrence to sk->sk_net. It has already
+ * been dropped in netlink_kernel_create. Taking referrence to stopping
+ * namespace is not an option.
+ * Take referrence to a socket to remove it from netlink lookup table
+ * _alive_ and after that destroy it in the context of init_net.
+ */
+ sock_hold(sk);
sock_release(sk->sk_socket);
+
+ sk->sk_net = get_net(&init_net);
+ sock_put(sk);
}
EXPORT_SYMBOL(netlink_kernel_release);