From 86741ec25462e4c8cdce6df2f41ead05568c7d5e Mon Sep 17 00:00:00 2001 From: Lorenzo Colitti Date: Fri, 4 Nov 2016 02:23:41 +0900 Subject: [PATCH] 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 --- include/net/sock.h | 7 +++++++ net/core/sock.c | 5 ++++- net/socket.c | 14 ++++++++++++++ 3 files changed, 25 insertions(+), 1 deletion(-) diff --git a/include/net/sock.h b/include/net/sock.h index 93331a1492db..cf617ee16723 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -419,6 +419,7 @@ struct sock { u32 sk_max_ack_backlog; __u32 sk_priority; __u32 sk_mark; + kuid_t sk_uid; struct pid *sk_peer_pid; const struct cred *sk_peer_cred; long sk_rcvtimeo; @@ -1664,6 +1665,7 @@ static inline void sock_graft(struct sock *sk, struct socket *parent) sk->sk_wq = parent->wq; parent->sk = sk; sk_set_socket(sk, parent); + sk->sk_uid = SOCK_INODE(parent)->i_uid; security_sock_graft(sk, parent); write_unlock_bh(&sk->sk_callback_lock); } @@ -1671,6 +1673,11 @@ static inline void sock_graft(struct sock *sk, struct socket *parent) kuid_t sock_i_uid(struct sock *sk); unsigned long sock_i_ino(struct sock *sk); +static inline kuid_t sock_net_uid(const struct net *net, const struct sock *sk) +{ + return sk ? sk->sk_uid : make_kuid(net->user_ns, 0); +} + static inline u32 net_tx_rndhash(void) { u32 v = prandom_u32(); 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, diff --git a/net/socket.c b/net/socket.c index 970a7ea3fc4a..4ce33c35e606 100644 --- a/net/socket.c +++ b/net/socket.c @@ -518,8 +518,22 @@ static ssize_t sockfs_listxattr(struct dentry *dentry, char *buffer, return used; } +int sockfs_setattr(struct dentry *dentry, struct iattr *iattr) +{ + int err = simple_setattr(dentry, iattr); + + if (!err) { + struct socket *sock = SOCKET_I(d_inode(dentry)); + + sock->sk->sk_uid = iattr->ia_uid; + } + + return err; +} + static const struct inode_operations sockfs_inode_ops = { .listxattr = sockfs_listxattr, + .setattr = sockfs_setattr, }; /** -- 2.20.1