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Commit 356fb77c authored by Lorenzo Colitti's avatar Lorenzo Colitti Committed by Amit Pundir
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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.

Bug: 16355602
Change-Id: Idbc3e9a0cec91c4c6e01916b967b6237645ebe59
Signed-off-by: default avatarLorenzo Colitti <lorenzo@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 782469bf

include/net/sock.h

+7 −0
Original line number Diff line number Diff line
@@ -423,6 +423,7 @@ struct sock { 
	void			*sk_security;

#endif

	__u32			sk_mark;

	kuid_t			sk_uid;

	u32			sk_classid;

	struct cg_proto		*sk_cgrp;

	void			(*sk_state_change)(struct sock *sk);
@@ -1737,6 +1738,7 @@ 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);

}
@@ -1744,6 +1746,11 @@ 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 struct dst_entry *

__sk_dst_get(struct sock *sk)

{

net/core/sock.c

+4 −1
Original line number Diff line number Diff line
@@ -2292,8 +2292,11 @@ 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);

	}



	spin_lock_init(&sk->sk_dst_lock);

	rwlock_init(&sk->sk_callback_lock);

net/socket.c

+14 −0
Original line number Diff line number Diff line
@@ -524,9 +524,23 @@ 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(dentry->d_inode);



		sock->sk->sk_uid = iattr->ia_uid;

	}



	return err;

}



static const struct inode_operations sockfs_inode_ops = {

	.getxattr = sockfs_getxattr,

	.listxattr = sockfs_listxattr,

	.setattr = sockfs_setattr,

};



/**