kerndat: Check that "/proc/[pid]/status" file has NS{pid, ..} lines

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.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>

NSpid is not (yet) supported on Centos7 thus we need this check for
compatibility.

(cherry-picked from Virtuozzo criu commit
https://src.openvz.org/projects/OVZ/repos/criu/commits/94f4653f20)

Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>

criu/cr-check.c

@@ -1346,6 +1346,17 @@ static int check_pidfd_store(void)
 	return 0;
 }
 
+static int check_ns_pid(void)
+{
+	if (kerndat_has_nspid() < 0)
+		return -1;
+
+	if (!kdat.has_nspid)
+		return -1;
+
+	return 0;
+}
+
 static int (*chk_feature)(void);
 
 /*
@@ -1459,6 +1470,7 @@ int cr_check(void)
 		ret |= check_time_namespace();
 		ret |= check_newifindex();
 		ret |= check_pidfd_store();
+		ret |= check_ns_pid();
 	}
 
 	/*
@@ -1568,6 +1580,7 @@ static struct feature_list feature_list[] = {
 	{ "nftables", check_nftables_cr },
 	{ "has_ipt_legacy", check_ipt_legacy },
 	{ "pidfd_store", check_pidfd_store },
+	{ "ns_pid", check_ns_pid },
 	{ NULL, NULL },
 };
 

criu/include/kerndat.h

@@ -71,6 +71,7 @@ struct kerndat_s {
 	bool has_newifindex;
 	bool has_pidfd_open;
 	bool has_pidfd_getfd;
+	bool has_nspid;
 };
 
 extern struct kerndat_s kdat;
@@ -91,4 +92,6 @@ enum {
  */
 extern int kerndat_fs_virtualized(unsigned int which, u32 kdev);
 
+extern int kerndat_has_nspid(void);
+
 #endif /* __CR_KERNDAT_H__ */

criu/kerndat.c

@@ -1133,6 +1133,33 @@ out:
 	return ret;
 }
 
+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;
@@ -1276,6 +1303,10 @@ int kerndat_init(void)
 	}
 	if (!ret)
 		kerndat_has_pidfd_open();
+	if (!ret && kerndat_has_nspid()) {
+		pr_err("kerndat_has_nspid failed when initializing kerndat.\n");
+		ret = -1;
+	}
 
 	kerndat_lsm();
 	kerndat_mmap_min_addr();

criu/namespaces.c

@@ -27,6 +27,7 @@
 #include "net.h"
 #include "cgroup.h"
 #include "fdstore.h"
+#include "kerndat.h"
 
 #include "protobuf.h"
 #include "util.h"