[Devel] [PATCH] nfsd: check passed socket's net matches NFSd superblock's one

[J. Bruce Fields]

Applying, sorry for the delay.--b.

On Wed, Feb 26, 2014 at 04:50:01PM +0300, Stanislav Kinsbursky wrote:
> There could be a case, when NFSd file system is mounted in network, different
> to socket's one, like below:
> 
> "ip netns exec" creates new network and mount namespace, which duplicates NFSd
> mount point, created in init_net context. And thus NFS server stop in nested
> network context leads to RPCBIND client destruction in init_net.
> Then, on NFSd start in nested network context, rpc.nfsd process creates socket
> in nested net and passes it into "write_ports", which leads to RPCBIND sockets
> creation in init_net context because of the same reason (NFSd monut point was
> created in init_net context). An attempt to register passed socket in nested
> net leads to panic, because no RPCBIND client present in nexted network
> namespace.
> 
> This patch add check that passed socket's net matches NFSd superblock's one.
> And returns -EINVAL error to user psace otherwise.
> 
> v2: Put socket on exit.
> 
> Reported-by: Weng Meiling <wengmeiling.weng at huawei.com>
> Signed-off-by: Stanislav Kinsbursky <skinsbursky at parallels.com>
> Cc: stable at vger.kernel.org
> ---
>  fs/nfsd/nfsctl.c               |    5 +++++
>  include/linux/sunrpc/svcsock.h |    1 +
>  net/sunrpc/svcsock.c           |   16 ++++++++++++++++
>  3 files changed, 22 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index 7f55517..f34d9de 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -699,6 +699,11 @@ static ssize_t __write_ports_addfd(char *buf, struct net *net)
>  	if (err != 0 || fd < 0)
>  		return -EINVAL;
>  
> +	if (svc_alien_sock(net, fd)) {
> +		printk(KERN_ERR "%s: socket net is different to NFSd's one\n", __func__);
> +		return -EINVAL;
> +	}
> +
>  	err = nfsd_create_serv(net);
>  	if (err != 0)
>  		return err;
> diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
> index 62fd1b7..947009e 100644
> --- a/include/linux/sunrpc/svcsock.h
> +++ b/include/linux/sunrpc/svcsock.h
> @@ -56,6 +56,7 @@ int		svc_recv(struct svc_rqst *, long);
>  int		svc_send(struct svc_rqst *);
>  void		svc_drop(struct svc_rqst *);
>  void		svc_sock_update_bufs(struct svc_serv *serv);
> +bool		svc_alien_sock(struct net *net, int fd);
>  int		svc_addsock(struct svc_serv *serv, const int fd,
>  					char *name_return, const size_t len);
>  void		svc_init_xprt_sock(void);
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index b6e59f0..d06cb87 100644
> --- a/net/sunrpc/svcsock.c
> +++ b/net/sunrpc/svcsock.c
> @@ -1397,6 +1397,22 @@ static struct svc_sock *svc_setup_socket(struct svc_serv *serv,
>  	return svsk;
>  }
>  
> +bool svc_alien_sock(struct net *net, int fd)
> +{
> +	int err;
> +	struct socket *sock = sockfd_lookup(fd, &err);
> +	bool ret = false;
> +
> +	if (!sock)
> +		goto out;
> +	if (sock_net(sock->sk) != net)
> +		ret = true;
> +	sockfd_put(sock);
> +out:
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(svc_alien_sock);
> +
>  /**
>   * svc_addsock - add a listener socket to an RPC service
>   * @serv: pointer to RPC service to which to add a new listener
>