[CRIU] [PATCH v4 03/31] ns: Set nested namespaces hookups

[Andrei Vagin]

On Wed, Feb 22, 2017 at 02:30:51PM +0300, Kirill Tkhai wrote:
> Introduce ns_id::parent and assign a pointer to parent
> for every ns except NS_CRIU and NS_ROOT.
> Also populate user_ns for pid_ns.
> 
> v4: Set "ret = -1" on one of the error pathes.
>     Add comment about user_ns finding.
> 
> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> ---
>  criu/include/namespaces.h |   12 ++++++
>  criu/namespaces.c         |   92 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 104 insertions(+)
> 
> diff --git a/criu/include/namespaces.h b/criu/include/namespaces.h
> index 1b454e0c1..69df0313b 100644
> --- a/criu/include/namespaces.h
> +++ b/criu/include/namespaces.h
> @@ -1,6 +1,8 @@
>  #ifndef __CR_NS_H__
>  #define __CR_NS_H__
>  
> +#include <sys/ioctl.h>
> +
>  #include "common/compiler.h"
>  #include "files.h"
>  #include "common/list.h"
> @@ -40,6 +42,12 @@
>  
>  #define EXTRA_SIZE	20
>  
> +#ifndef NSIO
> +#define NSIO    0xb7
> +#define NS_GET_USERNS   _IO(NSIO, 0x1)
> +#define NS_GET_PARENT   _IO(NSIO, 0x2)
> +#endif
> +
>  struct ns_desc {
>  	unsigned int	cflag;
>  	char		*str;
> @@ -76,6 +84,10 @@ struct ns_id {
>  	unsigned int id;
>  	pid_t ns_pid;
>  	struct ns_desc *nd;
> +	struct ns_id *parent;
> +	struct list_head children;
> +	struct list_head siblings;
> +	struct ns_id *user_ns;
>  	struct ns_id *next;
>  	enum ns_type type;
>  
> diff --git a/criu/namespaces.c b/criu/namespaces.c
> index b22162a3a..dd9fb7680 100644
> --- a/criu/namespaces.c
> +++ b/criu/namespaces.c
> @@ -13,6 +13,7 @@
>  #include <sys/stat.h>
>  #include <limits.h>
>  #include <errno.h>
> +#include <sys/ioctl.h>
>  
>  #include "page.h"
>  #include "rst-malloc.h"
> @@ -302,6 +303,8 @@ struct ns_id *rst_new_ns_id(unsigned int id, pid_t pid,
>  		nsid->type = type;
>  		nsid_add(nsid, nd, id, pid);
>  		nsid->ns_populated = false;
> +		INIT_LIST_HEAD(&nsid->children);
> +		INIT_LIST_HEAD(&nsid->siblings);
>  	}
>  
>  	return nsid;
> @@ -421,6 +424,8 @@ static unsigned int generate_ns_id(int pid, unsigned int kid, struct ns_desc *nd
>  	nsid->type = type;
>  	nsid->kid = kid;
>  	nsid->ns_populated = true;
> +	INIT_LIST_HEAD(&nsid->children);
> +	INIT_LIST_HEAD(&nsid->siblings);
>  	nsid_add(nsid, nd, ns_next_id++, pid);
>  
>  found:
> @@ -661,6 +666,93 @@ int dump_task_ns_ids(struct pstree_item *item)
>  	return 0;
>  }
>  
> +static int set_ns_opt(int ns_fd, unsigned ioc, struct ns_id **ns, struct ns_desc *nd)
> +{
> +	int opt_fd, ret = -1;
> +	struct stat st;
> +
> +	opt_fd = ioctl(ns_fd, ioc);
> +	if (opt_fd < 0) {
> +		pr_info("Can't do ns ioctl %x\n", ioc);
> +		return -errno;
> +	}
> +	if (fstat(opt_fd, &st) < 0) {
> +		pr_perror("Unable to stat on ns fd");
> +		ret = -errno;
> +		goto out;
> +	}
> +	*ns = lookup_ns_by_kid(st.st_ino, nd);
> +	if (!*ns) {
> +		pr_err("Namespaces hierarhies with holes are not supported\n");
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +	ret = 0;
> +out:
> +	close(opt_fd);
> +	return ret;
> +}
> +
> +static int set_ns_hookups(struct ns_id *ns)
> +{
> +	struct ns_desc *nd = ns->nd;
> +	struct ns_id *u_ns;
> +	int fd, ret = -1;
> +
> +	fd = open_proc(ns->ns_pid, "ns/%s", nd->str);
> +	if (fd < 0) {
> +		pr_perror("Can't open %s, pid %d", nd->str, ns->ns_pid);
> +		return -1;
> +	}
> +
> +	if (ns->type != NS_ROOT && (nd == &pid_ns_desc || nd == &user_ns_desc)) {
> +		if (set_ns_opt(fd, NS_GET_PARENT, &ns->parent, nd) < 0)
> +			goto out;
> +		if (ns->parent && ns->parent->type == NS_CRIU) {
> +			pr_err("Wrong determined NS_ROOT, or root_item has NS_OTHER user_ns\n");
> +			goto out;
> +		}

CID 176742:  Null pointer dereferences  (FORWARD_NULL)
Comparing "ns->parent" to null implies that "ns->parent" might
be null.

> +		list_add(&ns->siblings, &ns->parent->children);
> +	}
> +
> +	if (nd != &user_ns_desc) {
> +		ret = set_ns_opt(fd, NS_GET_USERNS, &ns->user_ns, &user_ns_desc);
> +		if (ret == -ENOTTY) {
> +			u_ns = NULL;
> +			if (root_ns_mask & CLONE_NEWUSER) {
> +				/*
> +				 * Assume, we have the only user_ns. If it's not so,
> +				 * we'll later fail on NS_GET_PARENT for the second user_ns.
> +				 */
> +				pr_info("Can't get user_ns of %s %u, assuming NS_ROOT\n",
> +					nd->str, ns->id);
> +				for (u_ns = ns_ids; u_ns; u_ns = u_ns->next) {
> +					if (u_ns->nd == &user_ns_desc && u_ns->type == NS_ROOT)
> +						break;
> +				}
> +				if (!u_ns) {
> +					pr_err("Can't find root user_ns\n");
> +					goto out;
> +				}
> +			}
> +			ns->user_ns = u_ns;
> +		} else if (ret < 0) {
> +			goto out;
> +		} else if (ns->user_ns->type == NS_CRIU) {
> +			if (root_ns_mask & CLONE_NEWUSER) {
> +				pr_err("Must not be criu user_ns\n");
> +				ret = -1;
> +				goto out;
> +			}
> +			ns->user_ns = NULL;
> +		}
> +	}
> +	ret = 0;
> +out:
> +	close(fd);
> +	return ret;
> +}
> +
>  static UsernsEntry userns_entry = USERNS_ENTRY__INIT;
>  #define INVALID_ID (~0U)
>  
>