[RFC PATCH 1/2] unix sockets: add ability for search for peer from passed root

[Stanislav Kinsbursky <skinsbursky@parallels.com>]

This helper is used stream sockets yet.
All is simple: if non-NULL struct path was passed to unix_find_other(), then
vfs_path_lookup() is called instead of kern_path().

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
---
 include/net/af_unix.h |    2 ++
 net/unix/af_unix.c    |   25 ++++++++++++++++++-------
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index 2ee33da..559467e 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -67,6 +67,8 @@ struct unix_sock {
 
 long unix_inq_len(struct sock *sk);
 long unix_outq_len(struct sock *sk);
+int unix_stream_connect_root(struct path *root, struct socket *sock,
+			     struct sockaddr *uaddr, int addr_len, int flags);
 
 #ifdef CONFIG_SYSCTL
 extern int unix_sysctl_register(struct net *net);
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 641f2e4..a790ebc 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -759,7 +759,7 @@ out:	mutex_unlock(&u->readlock);
 	return err;
 }
 
-static struct sock *unix_find_other(struct net *net,
+static struct sock *unix_find_other(struct net *net, struct path *root,
 				    struct sockaddr_un *sunname, int len,
 				    int type, unsigned int hash, int *error)
 {
@@ -769,7 +769,11 @@ static struct sock *unix_find_other(struct net *net,
 
 	if (sunname->sun_path[0]) {
 		struct inode *inode;
-		err = kern_path(sunname->sun_path, LOOKUP_FOLLOW, &path);
+
+		if (root)
+			err = vfs_path_lookup(root->dentry, root->mnt, sunname->sun_path, LOOKUP_FOLLOW, &path);
+		else
+			err = kern_path(sunname->sun_path, LOOKUP_FOLLOW, &path);
 		if (err)
 			goto fail;
 		inode = path.dentry->d_inode;
@@ -979,7 +983,7 @@ static int unix_dgram_connect(struct socket *sock, struct sockaddr *addr,
 			goto out;
 
 restart:
-		other = unix_find_other(net, sunaddr, alen, sock->type, hash, &err);
+		other = unix_find_other(net, NULL, sunaddr, alen, sock->type, hash, &err);
 		if (!other)
 			goto out;
 
@@ -1053,8 +1057,8 @@ static long unix_wait_for_peer(struct sock *other, long timeo)
 	return timeo;
 }
 
-static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
-			       int addr_len, int flags)
+int unix_stream_connect_root(struct path *root, struct socket *sock,
+			     struct sockaddr *uaddr, int addr_len, int flags)
 {
 	struct sockaddr_un *sunaddr = (struct sockaddr_un *)uaddr;
 	struct sock *sk = sock->sk;
@@ -1098,7 +1102,7 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 
 restart:
 	/*  Find listening sock. */
-	other = unix_find_other(net, sunaddr, addr_len, sk->sk_type, hash, &err);
+	other = unix_find_other(net, root, sunaddr, addr_len, sk->sk_type, hash, &err);
 	if (!other)
 		goto out;
 
@@ -1227,6 +1231,13 @@ out:
 		sock_put(other);
 	return err;
 }
+EXPORT_SYMBOL_GPL(unix_stream_connect_root);
+
+static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
+				    int addr_len, int flags)
+{
+	return unix_stream_connect_root(NULL, sock, uaddr, addr_len, flags);
+}
 
 static int unix_socketpair(struct socket *socka, struct socket *sockb)
 {
@@ -1508,7 +1519,7 @@ restart:
 		if (sunaddr == NULL)
 			goto out_free;
 
-		other = unix_find_other(net, sunaddr, namelen, sk->sk_type,
+		other = unix_find_other(net, NULL, sunaddr, namelen, sk->sk_type,
 					hash, &err);
 		if (other == NULL)
 			goto out_free;