[CRIU] [PATCH 1/4] sk-unix: Save mnt_id for bindmounted entries

[Andrey Vagin]

On Tue, Aug 08, 2017 at 02:25:07PM +0300, Cyrill Gorcunov wrote:
> Mount points might be beindmount to some resources (say unix binded
> sockets) thus when times come to do real bind mount call we need
> to prepare appropriate resource first.
> 
> On dump procedure we walk over all bind-mounts and check if
> the mountpoint is a unix socket saving the mnt_id into the image
> then.
> 
> Note at moment we support only DGRAM closed sockets.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
> ---
>  criu/cr-dump.c         |  3 +++
>  criu/include/sockets.h |  1 +
>  criu/sk-unix.c         | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  images/sk-unix.proto   |  5 ++++
>  4 files changed, 78 insertions(+)
> 
> diff --git a/criu/cr-dump.c b/criu/cr-dump.c
> index 06f3966c05cf..52857dc6c1c7 100644
> --- a/criu/cr-dump.c
> +++ b/criu/cr-dump.c
> @@ -1898,6 +1898,9 @@ int cr_dump_tasks(pid_t pid)
>  	if (collect_namespaces(true) < 0)
>  		goto err;
>  
> +	if (collect_unix_bindmounts() < 0)
> +		goto err;
> +
>  	glob_imgset = cr_glob_imgset_open(O_DUMP);
>  	if (!glob_imgset)
>  		goto err;
> diff --git a/criu/include/sockets.h b/criu/include/sockets.h
> index 9881d5bf3bc1..64673c5e5dc8 100644
> --- a/criu/include/sockets.h
> +++ b/criu/include/sockets.h
> @@ -37,6 +37,7 @@ extern int collect_sockets(struct ns_id *);
>  extern struct collect_image_info inet_sk_cinfo;
>  extern struct collect_image_info unix_sk_cinfo;
>  extern int fix_external_unix_sockets(void);
> +extern int collect_unix_bindmounts(void);
>  
>  extern struct collect_image_info netlink_sk_cinfo;
>  
> diff --git a/criu/sk-unix.c b/criu/sk-unix.c
> index 765d9ae9bddc..bf013c5ca4de 100644
> --- a/criu/sk-unix.c
> +++ b/criu/sk-unix.c
> @@ -86,6 +86,10 @@ struct unix_sk_desc {
>  	struct list_head	peer_node;
>  
>  	UnixSkEntry		*ue;
> +
> +	/* To handle bindmounts over socks */
> +	struct unix_diag_vfs	uv;		/* FIXME merge with rel_name_desc_t */
> +	int			mnt_id;
>  };
>  
>  static LIST_HEAD(unix_sockets);
> @@ -314,6 +318,11 @@ static int dump_one_unix_fd(int lfd, u32 id, const struct fd_parms *p)
>  	ue->opts	= skopts;
>  	ue->uflags	= 0;
>  
> +	if (sk->mnt_id) {
> +		ue->has_mnt_id	= true;
> +		ue->mnt_id	= sk->mnt_id;
> +	}
> +
>  	if (sk->rel_name) {
>  		if (resolve_rel_name(sk, p))
>  			goto err;
> @@ -533,6 +542,8 @@ static int unix_process_name(struct unix_sk_desc *d, const struct unix_diag_msg
>  		}
>  
>  		uv = RTA_DATA(tb[UNIX_DIAG_VFS]);
> +		memcpy(&d->uv, uv, sizeof(d->uv));
> +
>  		if (name[0] != '/') {
>  			/*
>  			 * Relative names are be resolved later at first
> @@ -787,6 +798,64 @@ int fix_external_unix_sockets(void)
>  	return -1;
>  }
>  
> +int collect_unix_bindmounts(void)
> +{
> +	int mntns_fd, old_ns = -1;
> +	struct mount_info *mi;
> +	struct stat st = {};
> +	int ret = 0;
> +
> +	for (mi = mntinfo; mi; mi = mi->next) {
> +		if (list_empty(&mi->mnt_bind))
> +			continue;
> +
> +		mntns_fd = open_proc(mi->nsid->ns_pid, "ns/mnt");
> +		if (mntns_fd < 0) {
> +			pr_err("Can't open %d/ns/mnt\n", mi->nsid->ns_pid);
> +			return -1;
> +		}
> +
> +		if (switch_ns_by_fd(mntns_fd, &mnt_ns_desc, &old_ns)) {
> +			pr_err("Can't switch mount ns for %d\n", mi->nsid->ns_pid);
> +			return -1;
> +		}
> +
> +		if (stat(mi->mountpoint, &st)) {
> +			pr_perror("Can't stat on %s", mi->mountpoint);
> +			return switch_ns_by_fd(old_ns, &mnt_ns_desc, NULL);
> +		}
> +
> +		if (S_ISSOCK(st.st_mode)) {
> +			struct unix_sk_desc *sk;
> +
> +			list_for_each_entry(sk, &unix_sockets, list) {
> +				if (sk->uv.udiag_vfs_ino == (int)st.st_ino &&
> +				    sk->uv.udiag_vfs_dev == (int)st.st_dev) {
> +					pr_debug("Found sock s_dev %#x ino %#x bindmounted mnt_id %d %s\n",
> +						 (int)st.st_dev, (int)st.st_ino, mi->mnt_id, mi->mountpoint);
> +					sk->mnt_id = mi->mnt_id;
> +					if (sk->type != SOCK_DGRAM && sk->state != TCP_CLOSE) {
> +						pr_err("Unsupported bindmounted socket ino %#x at %s\n",
> +						       (int)st.st_ino, mi->mountpoint);
> +						ret = -1;
> +						break;
> +					}
> +				}
> +			}

You have to report an error, if you can't find a socker.

> +		}
> +
> +		if (switch_ns_by_fd(old_ns, &mnt_ns_desc, NULL)) {
> +			pr_err("Can't switch mount ns back from %d\n", mi->nsid->ns_pid);
> +			return -1;
> +		}
> +
> +		if (ret)
> +			break;
> +	}
> +
> +	return ret;
> +}
> +
>  struct unix_sk_info {
>  	UnixSkEntry *ue;
>  	struct list_head list;
> diff --git a/images/sk-unix.proto b/images/sk-unix.proto
> index 2a33fe220d1e..9186e23f4062 100644
> --- a/images/sk-unix.proto
> +++ b/images/sk-unix.proto
> @@ -50,4 +50,9 @@ message unix_sk_entry {
>  	optional bool			deleted		= 15;
>  
>  	optional uint32			ns_id		= 16;
> +
> +	/*
> +	 * Bind-mounted sockets.
> +	 */
> +	optional uint32			mnt_id		= 17;

A socket can be bind-mounted in a few places.

>  }
> -- 
> 2.7.5
>