[Devel] Re: [PATCH v2] SUNRPC: check current nsproxy before set of node name on client creation

[Jeff Layton]

On Mon, 13 Aug 2012 15:37:31 +0400
Stanislav Kinsbursky <skinsbursky at parallels.com> wrote:

> v2:
> 1) rpc_clnt_set_nodename() prototype updated.
> 2) fixed errors in comment.
> 
> When child reaper exits, it can destroy mount namespace it belongs to, and if
> there are NFS mounts inside, then it will try to umount them. But in this
> point current->nsproxy is set to NULL and all namespaces will be destroyed one
> by one. I.e. we can't dereference current->nsproxy to obtain uts namespace.
> 
> Signed-off-by: Stanislav Kinsbursky <skinsbursky at parallels.com>
> ---
>  net/sunrpc/clnt.c |   16 +++++++++++++---
>  1 files changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
> index 9a9676e..8fbcbc8 100644
> --- a/net/sunrpc/clnt.c
> +++ b/net/sunrpc/clnt.c
> @@ -277,8 +277,18 @@ void rpc_clients_notifier_unregister(void)
>  	return rpc_pipefs_notifier_unregister(&rpc_clients_block);
>  }
>  
> -static void rpc_clnt_set_nodename(struct rpc_clnt *clnt, const char *nodename)
> +static void rpc_clnt_set_nodename(struct rpc_clnt *clnt)
>  {
> +	const char *nodename;
> +
> +	/*
> +	 * We have to protect against dying child reaper, which has released
> +	 * its nsproxy already and is trying to destroy mount namespace.
> +	 */
> +	if (current->nsproxy == NULL)
> +		return;
> +
> +	nodename = utsname()->nodename;
>  	clnt->cl_nodelen = strlen(nodename);
>  	if (clnt->cl_nodelen > UNX_MAXNODENAME)
>  		clnt->cl_nodelen = UNX_MAXNODENAME;
> @@ -365,7 +375,7 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, stru
>  	}
>  
>  	/* save the nodename */
> -	rpc_clnt_set_nodename(clnt, utsname()->nodename);
> +	rpc_clnt_set_nodename(clnt);
>  	rpc_register_client(clnt);
>  	return clnt;
>  
> @@ -524,7 +534,7 @@ rpc_clone_client(struct rpc_clnt *clnt)
>  	err = rpc_setup_pipedir(new, clnt->cl_program->pipe_dir_name);
>  	if (err != 0)
>  		goto out_no_path;
> -	rpc_clnt_set_nodename(new, utsname()->nodename);
> +	rpc_clnt_set_nodename(new);
>  	if (new->cl_auth)
>  		atomic_inc(&new->cl_auth->au_count);
>  	atomic_inc(&clnt->cl_count);
> 
> --
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Acked-by: Jeff Layton <jlayton at redhat.com>