v4.19.13 snapshot.
diff --git a/tools/testing/selftests/nsfs/.gitignore b/tools/testing/selftests/nsfs/.gitignore
new file mode 100644
index 0000000..2ab2c82
--- /dev/null
+++ b/tools/testing/selftests/nsfs/.gitignore
@@ -0,0 +1,2 @@
+owner
+pidns
diff --git a/tools/testing/selftests/nsfs/Makefile b/tools/testing/selftests/nsfs/Makefile
new file mode 100644
index 0000000..9ff7c7f
--- /dev/null
+++ b/tools/testing/selftests/nsfs/Makefile
@@ -0,0 +1,5 @@
+TEST_GEN_PROGS := owner pidns
+
+CFLAGS := -Wall -Werror
+
+include ../lib.mk
diff --git a/tools/testing/selftests/nsfs/config b/tools/testing/selftests/nsfs/config
new file mode 100644
index 0000000..598d0a2
--- /dev/null
+++ b/tools/testing/selftests/nsfs/config
@@ -0,0 +1,3 @@
+CONFIG_USER_NS=y
+CONFIG_UTS_NS=y
+CONFIG_PID_NS=y
diff --git a/tools/testing/selftests/nsfs/owner.c b/tools/testing/selftests/nsfs/owner.c
new file mode 100644
index 0000000..96a976c
--- /dev/null
+++ b/tools/testing/selftests/nsfs/owner.c
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <sched.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+
+#define NSIO 0xb7
+#define NS_GET_USERNS _IO(NSIO, 0x1)
+
+#define pr_err(fmt, ...) \
+ ({ \
+ fprintf(stderr, "%s:%d:" fmt ": %m\n", \
+ __func__, __LINE__, ##__VA_ARGS__); \
+ 1; \
+ })
+
+int main(int argc, char *argvp[])
+{
+ int pfd[2], ns, uns, init_uns;
+ struct stat st1, st2;
+ char path[128];
+ pid_t pid;
+ char c;
+
+ if (pipe(pfd))
+ return 1;
+
+ pid = fork();
+ if (pid < 0)
+ return pr_err("fork");
+ if (pid == 0) {
+ prctl(PR_SET_PDEATHSIG, SIGKILL);
+ if (unshare(CLONE_NEWUTS | CLONE_NEWUSER))
+ return pr_err("unshare");
+ close(pfd[0]);
+ close(pfd[1]);
+ while (1)
+ sleep(1);
+ return 0;
+ }
+ close(pfd[1]);
+ if (read(pfd[0], &c, 1) != 0)
+ return pr_err("Unable to read from pipe");
+ close(pfd[0]);
+
+ snprintf(path, sizeof(path), "/proc/%d/ns/uts", pid);
+ ns = open(path, O_RDONLY);
+ if (ns < 0)
+ return pr_err("Unable to open %s", path);
+
+ uns = ioctl(ns, NS_GET_USERNS);
+ if (uns < 0)
+ return pr_err("Unable to get an owning user namespace");
+
+ if (fstat(uns, &st1))
+ return pr_err("fstat");
+
+ snprintf(path, sizeof(path), "/proc/%d/ns/user", pid);
+ if (stat(path, &st2))
+ return pr_err("stat");
+
+ if (st1.st_ino != st2.st_ino)
+ return pr_err("NS_GET_USERNS returned a wrong namespace");
+
+ init_uns = ioctl(uns, NS_GET_USERNS);
+ if (uns < 0)
+ return pr_err("Unable to get an owning user namespace");
+
+ if (ioctl(init_uns, NS_GET_USERNS) >= 0 || errno != EPERM)
+ return pr_err("Don't get EPERM");
+
+ if (unshare(CLONE_NEWUSER))
+ return pr_err("unshare");
+
+ if (ioctl(ns, NS_GET_USERNS) >= 0 || errno != EPERM)
+ return pr_err("Don't get EPERM");
+ if (ioctl(init_uns, NS_GET_USERNS) >= 0 || errno != EPERM)
+ return pr_err("Don't get EPERM");
+
+ kill(pid, SIGKILL);
+ wait(NULL);
+ return 0;
+}
diff --git a/tools/testing/selftests/nsfs/pidns.c b/tools/testing/selftests/nsfs/pidns.c
new file mode 100644
index 0000000..e0d86e1
--- /dev/null
+++ b/tools/testing/selftests/nsfs/pidns.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <sched.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+
+#define pr_err(fmt, ...) \
+ ({ \
+ fprintf(stderr, "%s:%d:" fmt ": %m\n", \
+ __func__, __LINE__, ##__VA_ARGS__); \
+ 1; \
+ })
+
+#define NSIO 0xb7
+#define NS_GET_USERNS _IO(NSIO, 0x1)
+#define NS_GET_PARENT _IO(NSIO, 0x2)
+
+#define __stack_aligned__ __attribute__((aligned(16)))
+struct cr_clone_arg {
+ char stack[128] __stack_aligned__;
+ char stack_ptr[0];
+};
+
+static int child(void *args)
+{
+ prctl(PR_SET_PDEATHSIG, SIGKILL);
+ while (1)
+ sleep(1);
+ exit(0);
+}
+
+int main(int argc, char *argv[])
+{
+ char *ns_strs[] = {"pid", "user"};
+ char path[] = "/proc/0123456789/ns/pid";
+ struct cr_clone_arg ca;
+ struct stat st1, st2;
+ int ns, pns, i;
+ pid_t pid;
+
+ pid = clone(child, ca.stack_ptr, CLONE_NEWUSER | CLONE_NEWPID | SIGCHLD, NULL);
+ if (pid < 0)
+ return pr_err("clone");
+
+ for (i = 0; i < 2; i++) {
+ snprintf(path, sizeof(path), "/proc/%d/ns/%s", pid, ns_strs[i]);
+ ns = open(path, O_RDONLY);
+ if (ns < 0)
+ return pr_err("Unable to open %s", path);
+
+ pns = ioctl(ns, NS_GET_PARENT);
+ if (pns < 0)
+ return pr_err("Unable to get a parent pidns");
+
+ snprintf(path, sizeof(path), "/proc/self/ns/%s", ns_strs[i]);
+ if (stat(path, &st2))
+ return pr_err("Unable to stat %s", path);
+ if (fstat(pns, &st1))
+ return pr_err("Unable to stat the parent pidns");
+ if (st1.st_ino != st2.st_ino)
+ return pr_err("NS_GET_PARENT returned a wrong namespace");
+
+ if (ioctl(pns, NS_GET_PARENT) >= 0 || errno != EPERM)
+ return pr_err("Don't get EPERM");
+ }
+
+ kill(pid, SIGKILL);
+ wait(NULL);
+ return 0;
+}