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

Eric W. Biederman
2019-02-19T16:42:17Z

David Howells <dhowells@redhat.com> writes:

> 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);
>

Nacked-by: "Eric W. Biederman" <ebiederm@xmission.com>

Use a namespace file descriptor if you need this. So far we have not
added this system call as it is just a performance optimization. And it
has been too niche to matter.

If this that has changed we can add this separately from everything else
you are doing here.

> 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]);