@@ -10,4 +10,6 @@ struct sockaddr_un {
char sun_path[UNIX_PATH_MAX]; /* pathname */
};
+#define SIOCUNIXFILE (SIOCPROTOPRIVATE + 0) /* open a socket file with O_PATH */
+
#endif /* _LINUX_UN_H */
@@ -117,6 +117,7 @@
#include <net/checksum.h>
#include <linux/security.h>
#include <linux/freezer.h>
+#include <linux/file.h>
struct hlist_head unix_socket_table[2 * UNIX_HASH_SIZE];
EXPORT_SYMBOL_GPL(unix_socket_table);
@@ -2592,6 +2593,43 @@ long unix_outq_len(struct sock *sk)
}
EXPORT_SYMBOL_GPL(unix_outq_len);
+static int unix_open_file(struct sock *sk)
+{
+ struct path path;
+ struct file *f;
+ int fd;
+
+ if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))
+ return -EPERM;
+
+ unix_state_lock(sk);
+ path = unix_sk(sk)->path;
+ if (!path.dentry) {
+ unix_state_unlock(sk);
+ return -ENOENT;
+ }
+
+ path_get(&path);
+ unix_state_unlock(sk);
+
+ fd = get_unused_fd_flags(O_CLOEXEC);
+ if (fd < 0)
+ goto out;
+
+ f = dentry_open(&path, O_PATH, current_cred());
+ if (IS_ERR(f)) {
+ put_unused_fd(fd);
+ fd = PTR_ERR(f);
+ goto out;
+ }
+
+ fd_install(fd, f);
+out:
+ path_put(&path);
+
+ return fd;
+}
+
static int unix_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
{
struct sock *sk = sock->sk;
@@ -2610,6 +2648,9 @@ static int unix_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
else
err = put_user(amount, (int __user *)arg);
break;
+ case SIOCUNIXFILE:
+ err = unix_open_file(sk);
+ break;
default:
err = -ENOIOCTLCMD;
break;
This ioctl opens a file to which a socket is bound and returns a file descriptor. The caller has to have CAP_NET_ADMIN in the socket network namespace. Currently it is impossible to get a path and a mount point for a socket file. socket_diag reports address, device ID and inode number for unix sockets. An address can contain a relative path or a file may be moved somewhere. And these properties say nothing about a mount namespace and a mount point of a socket file. With the introduced ioctl, we can get a path by reading /proc/self/fd/X and get mnt_id from /proc/self/fdinfo/X. In CRIU we are going to use this ioctl to dump and restore unix socket. Here is an example how it can be used: $ strace -e socket,bind,ioctl ./test /tmp/test_sock socket(AF_UNIX, SOCK_STREAM, 0) = 3 bind(3, {sa_family=AF_UNIX, sun_path="test_sock"}, 11) = 0 ioctl(3, SIOCUNIXFILE, 0) = 4 ^Z $ ss -a | grep test_sock u_str LISTEN 0 1 test_sock 17798 * 0 $ ls -l /proc/760/fd/{3,4} lrwx------ 1 root root 64 Feb 1 09:41 3 -> 'socket:[17798]' l--------- 1 root root 64 Feb 1 09:41 4 -> /tmp/test_sock $ cat /proc/760/fdinfo/4 pos: 0 flags: 012000000 mnt_id: 40 $ cat /proc/self/mountinfo | grep "^40\s" 40 19 0:37 / /tmp rw shared:23 - tmpfs tmpfs rw Signed-off-by: Andrei Vagin <avagin@openvz.org> --- include/uapi/linux/un.h | 2 ++ net/unix/af_unix.c | 41 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 43 insertions(+)