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author | Andrey Vagin <avagin@openvz.org> | 2017-02-01 22:00:45 +0300 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2017-02-03 05:58:02 +0300 |
commit | ba94f3088b792b16ea576a256a6030feddc87f24 (patch) | |
tree | 3295b00ebb6ddad72b5fa24c24d6c973598b91b8 /net | |
parent | 2a7b6216692cd66f4c94e6ebb48e43038349ca7d (diff) | |
download | linux-ba94f3088b792b16ea576a256a6030feddc87f24.tar.xz |
unix: add ioctl to open a unix socket file with O_PATH
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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r-- | net/unix/af_unix.c | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index cef79873b09d..e2d18b9f910f 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -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; |