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/socket.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'net/socket.c') 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, }; /** -- cgit v1.2.3-59-g8ed1b