[RFC PATCH 05/27] containers: Open a socket inside a container

David Howells
2019-02-15T16:08:04Z

Provide a system call to open a socket inside of a container, using that
container's network namespace. This allows netlink to be used to manage
the container.

fd = container_socket(int container_fd,
int domain, int type, int protocol);

Signed-off-by: David Howells <dhowells@redhat.com>
---

arch/x86/entry/syscalls/syscall_32.tbl | 1 +
arch/x86/entry/syscalls/syscall_64.tbl | 1 +
include/linux/socket.h | 3 ++-
include/linux/syscalls.h | 2 ++
kernel/sys_ni.c | 1 +
net/compat.c | 2 +-
net/socket.c | 34 +++++++++++++++++++++++++++-----
7 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 8666693510f9..f4c9beff77a6 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -409,3 +409,4 @@
395 i386 sb_notify sys_sb_notify __ia32_sys_sb_notify
396 i386 container_create sys_container_create __ia32_sys_container_create
397 i386 fork_into_container sys_fork_into_container __ia32_sys_fork_into_container
+398 i386 container_socket sys_container_socket __ia32_sys_container_socket
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index d40d4790fcb2..e20cdf7b5527 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -354,6 +354,7 @@
343 common sb_notify __x64_sys_sb_notify
344 common container_create __x64_sys_container_create
345 common fork_into_container __x64_sys_fork_into_container
+346 common container_socket __x64_sys_container_socket

#
# x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/include/linux/socket.h b/include/linux/socket.h
index ab2041a00e01..154ac900a8a5 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -10,6 +10,7 @@
#include <linux/compiler.h> /* __user */
#include <uapi/linux/socket.h>

+struct net;
struct pid;
struct cred;

@@ -376,7 +377,7 @@ extern int __sys_sendto(int fd, void __user *buff, size_t len,
int addr_len);
extern int __sys_accept4(int fd, struct sockaddr __user *upeer_sockaddr,
int __user *upeer_addrlen, int flags);
-extern int __sys_socket(int family, int type, int protocol);
+extern int __sys_socket(struct net *net, int family, int type, int protocol);
extern int __sys_bind(int fd, struct sockaddr __user *umyaddr, int addrlen);
extern int __sys_connect(int fd, struct sockaddr __user *uservaddr,
int addrlen);
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 15e5cc704df3..547334c6ffc2 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -947,6 +947,8 @@ asmlinkage long sys_container_create(const char __user *name, unsigned int flags
unsigned long spare3, unsigned long spare4,
unsigned long spare5);
asmlinkage long sys_fork_into_container(int containerfd);
+asmlinkage long sys_container_socket(int containerfd,
+ int domain, int type, int protocol);

/*
* Architecture-specific system calls
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index a23ad529d548..ce9c5bb30e7f 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -236,6 +236,7 @@ COND_SYSCALL(shmdt);
/* net/socket.c */
COND_SYSCALL(socket);
COND_SYSCALL(socketpair);
+COND_SYSCALL(container_socket);
COND_SYSCALL(bind);
COND_SYSCALL(listen);
COND_SYSCALL(accept);
diff --git a/net/compat.c b/net/compat.c
index 959d1c51826d..1b2db740fd33 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -856,7 +856,7 @@ COMPAT_SYSCALL_DEFINE2(socketcall, int, call, u32 __user *, args)

switch (call) {
case SYS_SOCKET:
- ret = __sys_socket(a0, a1, a[2]);
+ ret = __sys_socket(current->nsproxy->net_ns, a0, a1, a[2]);
break;
case SYS_BIND:
ret = __sys_bind(a0, compat_ptr(a1), a[2]);
diff --git a/net/socket.c b/net/socket.c
index 7d271a1d0c7e..7406580598b9 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -80,6 +80,7 @@
#include <linux/highmem.h>
#include <linux/mount.h>
#include <linux/fs_context.h>
+#include <linux/container.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/compat.h>
@@ -1326,9 +1327,9 @@ int sock_create_kern(struct net *net, int family, int type, int protocol, struct
}
EXPORT_SYMBOL(sock_create_kern);

-int __sys_socket(int family, int type, int protocol)
+int __sys_socket(struct net *net, int family, int type, int protocol)
{
- int retval;
+ long retval;
struct socket *sock;
int flags;

@@ -1346,7 +1347,7 @@ int __sys_socket(int family, int type, int protocol)
if (SOCK_NONBLOCK != O_NONBLOCK && (flags & SOCK_NONBLOCK))
flags = (flags & ~SOCK_NONBLOCK) | O_NONBLOCK;

- retval = sock_create(family, type, protocol, &sock);
+ retval = __sock_create(net, family, type, protocol, &sock, 0);
if (retval < 0)
return retval;

@@ -1355,9 +1356,32 @@ int __sys_socket(int family, int type, int protocol)

SYSCALL_DEFINE3(socket, int, family, int, type, int, protocol)
{
- return __sys_socket(family, type, protocol);
+ return __sys_socket(current->nsproxy->net_ns, family, type, protocol);
}

+/*
+ * Create a socket inside a container.
+ */
+#ifdef CONFIG_CONTAINERS
+SYSCALL_DEFINE4(container_socket,
+ int, containerfd, int, family, int, type, int, protocol)
+{
+ struct fd f = fdget(containerfd);
+ long ret;
+
+ if (!f.file)
+ return -EBADF;
+ ret = -EINVAL;
+ if (is_container_file(f.file)) {
+ struct container *c = f.file->private_data;
+
+ ret = __sys_socket(c->ns->net_ns, family, type, protocol);
+ }
+ fdput(f);
+ return ret;
+}
+#endif
+
/*
* Create a pair of connected sockets.
*/
@@ -2555,7 +2579,7 @@ SYSCALL_DEFINE2(socketcall, int, call, unsigned long __user *, args)

switch (call) {
case SYS_SOCKET:
- err = __sys_socket(a0, a1, a[2]);
+ err = __sys_socket(current->nsproxy->net_ns, a0, a1, a[2]);
break;
case SYS_BIND:
err = __sys_bind(a0, (struct sockaddr __user *)a1, a[2]);