[CRIU] [PATCH v2 09/57] kerndat: Check that "/proc/[pid]/status" file has NS{pid, ..} lines

[Andrei Vagin]

On Tue, Mar 28, 2017 at 06:35:32PM +0300, Kirill Tkhai wrote:
> If there is nested pid_ns, we need to be able to get pid in
> the whole pid hierarhy. This may be taken from "/proc/[pid]/status"
> file only. Check, that kernel has support for it.

Do we need to add a proper feature check

criu check --feature nspid



> 
> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> ---
>  criu/include/kerndat.h |    1 +
>  criu/kerndat.c         |   28 ++++++++++++++++++++++++++++
>  criu/namespaces.c      |    5 +++++
>  3 files changed, 34 insertions(+)
> 
> diff --git a/criu/include/kerndat.h b/criu/include/kerndat.h
> index 60c69c3e..2e8c3309 100644
> --- a/criu/include/kerndat.h
> +++ b/criu/include/kerndat.h
> @@ -43,6 +43,7 @@ struct kerndat_s {
>  	unsigned long uffd_features;
>  	bool has_nsid;
>  	bool has_link_nsid;
> +	bool has_nspid;
>  };
>  
>  extern struct kerndat_s kdat;
> diff --git a/criu/kerndat.c b/criu/kerndat.c
> index 354c2a5f..df388c56 100644
> --- a/criu/kerndat.c
> +++ b/criu/kerndat.c
> @@ -630,6 +630,32 @@ int kerndat_uffd(bool need_uffd)
>  	return 0;
>  }
>  
> +int kerndat_has_nspid(void)
> +{
> +	struct bfd f;
> +	int ret = -1;
> +	char *str;
> +
> +	f.fd = open("/proc/self/status", O_RDONLY);
> +	if (f.fd < 0) {
> +		pr_perror("Can't open /proc/self/status");
> +		return -1;
> +	}
> +	if (bfdopenr(&f))
> +		return -1;
> +	while ((str = breadline(&f)) != NULL) {
> +		if (IS_ERR(str))
> +			goto close;
> +		if (!strncmp(str, "NSpid:", 6)) {
> +			kdat.has_nspid = true;
> +			break;
> +		}
> +	}
> +	ret = 0;
> +close:
> +	bclose(&f);
> +	return ret;
> +}
>  int kerndat_init(void)
>  {
>  	int ret;
> @@ -661,6 +687,8 @@ int kerndat_init(void)
>  		ret = kerndat_socket_netns();
>  	if (!ret)
>  		ret = kerndat_nsid();
> +	if (!ret)
> +		ret = kerndat_has_nspid();
>  
>  	kerndat_lsm();
>  	kerndat_mmap_min_addr();
> diff --git a/criu/namespaces.c b/criu/namespaces.c
> index 4ecd6e36..1dab7656 100644
> --- a/criu/namespaces.c
> +++ b/criu/namespaces.c
> @@ -26,6 +26,7 @@
>  #include "namespaces.h"
>  #include "net.h"
>  #include "cgroup.h"
> +#include "kerndat.h"
>  
>  #include "protobuf.h"
>  #include "util.h"
> @@ -792,6 +793,10 @@ static int set_ns_hookups(struct ns_id *ns)
>  			pr_err("Wrong determined NS_ROOT, or root_item has NS_OTHER user_ns\n");
>  			goto out;
>  		}
> +		if (nd == &pid_ns_desc && !kdat.has_nspid) {
> +			pr_err("Can't dump nested pid ns\n");
> +			goto out;
> +		}
>  		list_add(&ns->siblings, &ns->parent->children);
>  	}
>  
>