Subject: [RFC PATCH 4/5] net: fbind() for unix sockets protocol operations introduced

From: Stanislav Kinsbursky <[email-masked]>
Date: Wed, 15 Aug 2012 20:22:20 +0400

Path for unix_address is taken from passed file.
File inode have to be socket.
Since no sunaddr is present, addr->name is constructed at the place. It
obviously means, then path name can be truncated is it's longer then
UNIX_MAX_PATH.

Signed-off-by: Stanislav Kinsbursky <[email-masked]>
---
 net/unix/af_unix.c |   78 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 76 insertions(+), 2 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index b26200d..2f34c9d 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -286,12 +286,11 @@ static inline struct sock *unix_find_socket_byname(struct net *net,
 	return s;
 }
 
-static struct sock *unix_find_socket_byinode(struct inode *i)
+static struct sock *__unix_find_socket_byinode(struct inode *i)
 {
 	struct sock *s;
 	struct hlist_node *node;
 
-	spin_lock(&unix_table_lock);
 	sk_for_each(s, node,
 		    &unix_socket_table[i->i_ino & (UNIX_HASH_SIZE - 1)]) {
 		struct dentry *dentry = unix_sk(s)->path.dentry;
@@ -303,6 +302,15 @@ static struct sock *unix_find_socket_byinode(struct inode *i)
 	}
 	s = NULL;
 found:
+	return s;
+}
+
+static struct sock *unix_find_socket_byinode(struct inode *i)
+{
+	struct sock *s;
+
+	spin_lock(&unix_table_lock);
+	s = __unix_find_socket_byinode(i);
 	spin_unlock(&unix_table_lock);
 	return s;
 }
@@ -502,6 +510,7 @@ out:
 
 static int unix_release(struct socket *);
 static int unix_bind(struct socket *, struct sockaddr *, int);
+static int unix_fbind(struct file *file, struct socket *sock);
 static int unix_stream_connect(struct socket *, struct sockaddr *,
 			       int addr_len, int flags);
 static int unix_socketpair(struct socket *, struct socket *);
@@ -542,6 +551,7 @@ static const struct proto_ops unix_stream_ops = {
 	.owner =	THIS_MODULE,
 	.release =	unix_release,
 	.bind =		unix_bind,
+	.fbind =	unix_fbind,
 	.connect =	unix_stream_connect,
 	.socketpair =	unix_socketpair,
 	.accept =	unix_accept,
@@ -564,6 +574,7 @@ static const struct proto_ops unix_dgram_ops = {
 	.owner =	THIS_MODULE,
 	.release =	unix_release,
 	.bind =		unix_bind,
+	.fbind =	unix_fbind,
 	.connect =	unix_dgram_connect,
 	.socketpair =	unix_socketpair,
 	.accept =	sock_no_accept,
@@ -586,6 +597,7 @@ static const struct proto_ops unix_seqpacket_ops = {
 	.owner =	THIS_MODULE,
 	.release =	unix_release,
 	.bind =		unix_bind,
+	.fbind =	unix_fbind,
 	.connect =	unix_stream_connect,
 	.socketpair =	unix_socketpair,
 	.accept =	unix_accept,
@@ -843,6 +855,68 @@ static int __unix_add_sock(struct path *path, struct sock *sk,
 
 }
 
+static int unix_fbind(struct file *f, struct socket *sock)
+{
+	struct sock *sk = sock->sk, *tmp;
+	struct unix_sock *u = unix_sk(sk);
+	struct unix_address *addr;
+	struct path *path = &f->f_path;
+	struct inode *inode = path->dentry->d_inode;
+	char *buf, *name;
+	int err;
+
+	err = -ENOTSOCK;
+	if (!S_ISSOCK(inode->i_mode))
+		goto out;
+
+	mutex_lock(&u->readlock);
+
+	err = -EINVAL;
+	if (u->addr)
+		goto out_up;
+
+	err = -ENOMEM;
+	buf = (char*)__get_free_page(GFP_KERNEL);
+	if (!buf)
+		goto out_up;
+
+	err = -EFAULT;
+	name = d_path(path, buf, PAGE_SIZE);
+	if (IS_ERR(name))
+		goto out_up_page;
+
+	addr = kmalloc(sizeof(*addr) + sizeof(struct sockaddr_un), GFP_KERNEL);
+	if (!addr)
+		goto out_up_page;
+
+	addr->name->sun_family = AF_UNIX;
+	addr->len = min(strlen(name), (size_t)UNIX_PATH_MAX);
+	memcpy(addr->name->sun_path, name, addr->len);
+	atomic_set(&addr->refcnt, 1);
+
+	spin_lock(&unix_table_lock);
+
+	err = -EADDRINUSE;
+	tmp = __unix_find_socket_byinode(inode);
+	if (tmp) {
+		sock_put(tmp);
+		unix_release_addr(addr);
+		goto out_unlock;
+	}
+
+	err = __unix_add_sock(path, sk, addr, 0);
+	path_get(path);
+
+out_unlock:
+	spin_unlock(&unix_table_lock);
+out_up_page:
+	free_page((unsigned long)buf);
+out_up:
+	mutex_unlock(&u->readlock);
+out:
+	return err;
+}
+
 static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 {
 	struct sock *sk = sock->sk;