From 86741ec25462e4c8cdce6df2f41ead05568c7d5e Mon Sep 17 00:00:00 2001 From: Lorenzo Colitti Date: Fri, 4 Nov 2016 02:23:41 +0900 Subject: net: core: Add a UID field to struct sock. Protocol sockets (struct sock) don't have UIDs, but most of the time, they map 1:1 to userspace sockets (struct socket) which do. Various operations such as the iptables xt_owner match need access to the "UID of a socket", and do so by following the backpointer to the struct socket. This involves taking sk_callback_lock and doesn't work when there is no socket because userspace has already called close(). Simplify this by adding a sk_uid field to struct sock whose value matches the UID of the corresponding struct socket. The semantics are as follows: 1. Whenever sk_socket is non-null: sk_uid is the same as the UID in sk_socket, i.e., matches the return value of sock_i_uid. Specifically, the UID is set when userspace calls socket(), fchown(), or accept(). 2. When sk_socket is NULL, sk_uid is defined as follows: - For a socket that no longer has a sk_socket because userspace has called close(): the previous UID. - For a cloned socket (e.g., an incoming connection that is established but on which userspace has not yet called accept): the UID of the socket it was cloned from. - For a socket that has never had an sk_socket: UID 0 inside the user namespace corresponding to the network namespace the socket belongs to. Kernel sockets created by sock_create_kern are a special case of #1 and sk_uid is the user that created them. For kernel sockets created at network namespace creation time, such as the per-processor ICMP and TCP sockets, this is the user that created the network namespace. Signed-off-by: Lorenzo Colitti Signed-off-by: David S. Miller --- net/core/sock.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'net/core/sock.c') diff --git a/net/core/sock.c b/net/core/sock.c index d8e4532e89e7..40dbc13453f9 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2460,8 +2460,11 @@ void sock_init_data(struct socket *sock, struct sock *sk) sk->sk_type = sock->type; sk->sk_wq = sock->wq; sock->sk = sk; - } else + sk->sk_uid = SOCK_INODE(sock)->i_uid; + } else { sk->sk_wq = NULL; + sk->sk_uid = make_kuid(sock_net(sk)->user_ns, 0); + } rwlock_init(&sk->sk_callback_lock); lockdep_set_class_and_name(&sk->sk_callback_lock, -- cgit v1.2.3