[PATCH v2 4/4] selftests/pidfd: add pidfd setns tests

From: Christian Brauner
Date: Thu Apr 30 2020 - 12:57:45 EST

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This is basically a test-suite for setns() and as of now contains:
- test that we can't pass garbage flags
- test that we can't attach to the namespaces of task that has already exited
- test that we can incrementally setns into all namespaces of a target task
using a pidfd
- test that we can setns atomically into all namespaces of a target task
- test that we can't cross setns into a user namespace outside of our user
namespace hierarchy
- test that we can't setns into namespaces owned by user namespaces over which
we are not privileged

Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
---
/* v2 */
patch introduced
---
tools/testing/selftests/pidfd/.gitignore | 1 +
tools/testing/selftests/pidfd/Makefile | 3 +-
tools/testing/selftests/pidfd/config | 6 +
.../selftests/pidfd/pidfd_setns_test.c | 422 ++++++++++++++++++
4 files changed, 431 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/pidfd/config
create mode 100644 tools/testing/selftests/pidfd/pidfd_setns_test.c

diff --git a/tools/testing/selftests/pidfd/.gitignore b/tools/testing/selftests/pidfd/.gitignore
index 2d4db5afb142..973198a3ec3d 100644
--- a/tools/testing/selftests/pidfd/.gitignore
+++ b/tools/testing/selftests/pidfd/.gitignore
@@ -5,3 +5,4 @@ pidfd_test
pidfd_wait
pidfd_fdinfo_test
pidfd_getfd_test
+pidfd_setns_test
diff --git a/tools/testing/selftests/pidfd/Makefile b/tools/testing/selftests/pidfd/Makefile
index 75a545861375..f4a2f28f926b 100644
--- a/tools/testing/selftests/pidfd/Makefile
+++ b/tools/testing/selftests/pidfd/Makefile
@@ -1,7 +1,8 @@
# SPDX-License-Identifier: GPL-2.0-only
CFLAGS += -g -I../../../../usr/include/ -pthread

-TEST_GEN_PROGS := pidfd_test pidfd_fdinfo_test pidfd_open_test pidfd_poll_test pidfd_wait pidfd_getfd_test
+TEST_GEN_PROGS := pidfd_test pidfd_fdinfo_test pidfd_open_test \
+ pidfd_poll_test pidfd_wait pidfd_getfd_test pidfd_setns_test

include ../lib.mk

diff --git a/tools/testing/selftests/pidfd/config b/tools/testing/selftests/pidfd/config
new file mode 100644
index 000000000000..bb11de90c0c9
--- /dev/null
+++ b/tools/testing/selftests/pidfd/config
@@ -0,0 +1,6 @@
+CONFIG_UTS_NS=y
+CONFIG_IPC_NS=y
+CONFIG_USER_NS=y
+CONFIG_PID_NS=y
+CONFIG_NET_NS=y
+CONFIG_CGROUPS=y
diff --git a/tools/testing/selftests/pidfd/pidfd_setns_test.c b/tools/testing/selftests/pidfd/pidfd_setns_test.c
new file mode 100644
index 000000000000..c327cc3b0ec9
--- /dev/null
+++ b/tools/testing/selftests/pidfd/pidfd_setns_test.c
@@ -0,0 +1,422 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <linux/types.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syscall.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <linux/kcmp.h>
+
+#include "pidfd.h"
+#include "../clone3/clone3_selftests.h"
+#include "../kselftest.h"
+#include "../kselftest_harness.h"
+
+enum {
+ PIDFD_NS_USER,
+ PIDFD_NS_MNT,
+ PIDFD_NS_PID,
+ PIDFD_NS_UTS,
+ PIDFD_NS_IPC,
+ PIDFD_NS_NET,
+ PIDFD_NS_CGROUP,
+ PIDFD_NS_PIDCLD,
+ PIDFD_NS_MAX
+};
+
+const struct ns_info {
+ const char *proc_name;
+ int clone_flag;
+ const char *flag_name;
+} ns_info[] = {
+ [PIDFD_NS_USER] = { "user", CLONE_NEWUSER, "CLONE_NEWUSER", },
+ [PIDFD_NS_MNT] = { "mnt", CLONE_NEWNS, "CLONE_NEWNS", },
+ [PIDFD_NS_PID] = { "pid", CLONE_NEWPID, "CLONE_NEWPID", },
+ [PIDFD_NS_UTS] = { "uts", CLONE_NEWUTS, "CLONE_NEWUTS", },
+ [PIDFD_NS_IPC] = { "ipc", CLONE_NEWIPC, "CLONE_NEWIPC", },
+ [PIDFD_NS_NET] = { "net", CLONE_NEWNET, "CLONE_NEWNET", },
+ [PIDFD_NS_CGROUP] = { "cgroup", CLONE_NEWCGROUP, "CLONE_NEWCGROUP", },
+ [PIDFD_NS_PIDCLD] = { "pid_for_children", 0, "INVALID_FLAG_PID_FOR_CHILDREN", },
+};
+
+FIXTURE(current_nsset)
+{
+ pid_t pid;
+ int pidfd;
+ int ns_fds[PIDFD_NS_MAX];
+
+ pid_t child_pid_exited;
+ int child_pidfd_exited;
+
+ pid_t child_pid_all_ns_stopped1;
+ int child_pidfd_all_ns_stopped1;
+ int child_ns_fds_all_ns_stopped1[PIDFD_NS_MAX];
+
+ pid_t child_pid_all_ns_stopped2;
+ int child_pidfd_all_ns_stopped2;
+ int child_ns_fds_all_ns_stopped2[PIDFD_NS_MAX];
+};
+
+static int sys_waitid(int which, pid_t pid, int options)
+{
+ return syscall(__NR_waitid, which, pid, NULL, options, NULL);
+}
+
+pid_t create_child(int *pidfd, unsigned flags)
+{
+ struct clone_args args = {
+ .flags = CLONE_PIDFD | flags,
+ .exit_signal = SIGCHLD,
+ .pidfd = ptr_to_u64(pidfd),
+ };
+
+ return sys_clone3(&args, sizeof(struct clone_args));
+}
+
+FIXTURE_SETUP(current_nsset)
+{
+ int i;
+ int proc_fd;
+
+ for (i = 0; i < PIDFD_NS_MAX; i++) {
+ self->ns_fds[i] = -EBADF;
+ self->child_ns_fds_all_ns_stopped1[i] = -EBADF;
+ self->child_ns_fds_all_ns_stopped2[i] = -EBADF;
+ }
+
+ proc_fd = open("/proc/self/ns", O_DIRECTORY | O_CLOEXEC);
+ ASSERT_GE(proc_fd, 0) {
+ TH_LOG("%m - Failed to open /proc/self/ns");
+ }
+
+ self->pid = getpid();
+ for (i = 0; i < PIDFD_NS_MAX; i++) {
+ const struct ns_info *info = &ns_info[i];
+ self->ns_fds[i] = openat(proc_fd, info->proc_name, O_RDONLY | O_CLOEXEC);
+ if (self->ns_fds[i] < 0) {
+ EXPECT_EQ(errno, ENOENT) {
+ TH_LOG("%m - Failed to open %s namespace for process %d",
+ info->proc_name, self->pid);
+ }
+ }
+ }
+
+ self->pidfd = sys_pidfd_open(self->pid, 0);
+ ASSERT_GE(self->pidfd, 0) {
+ TH_LOG("%m - Failed to open pidfd for process %d", self->pid);
+ }
+
+ /* Create task that exits right away. */
+ self->child_pid_exited = create_child(&self->child_pidfd_exited,
+ CLONE_NEWUSER | CLONE_NEWNET);
+ ASSERT_GE(self->child_pid_exited, 0);
+
+ if (self->child_pid_exited == 0)
+ _exit(EXIT_SUCCESS);
+
+ ASSERT_EQ(sys_waitid(P_PID, self->child_pid_exited, WEXITED | WNOWAIT), 0);
+
+ self->pidfd = sys_pidfd_open(self->pid, 0);
+ ASSERT_GE(self->pidfd, 0) {
+ TH_LOG("%m - Failed to open pidfd for process %d", self->pid);
+ }
+
+ /* Create tasks that will be stopped. */
+ self->child_pid_all_ns_stopped1 = create_child(&self->child_pidfd_all_ns_stopped1,
+ CLONE_NEWUSER |
+ CLONE_NEWNS |
+ CLONE_NEWCGROUP |
+ CLONE_NEWIPC |
+ CLONE_NEWUTS |
+ CLONE_NEWPID |
+ CLONE_NEWNET);
+ ASSERT_GE(self->child_pid_all_ns_stopped1, 0);
+
+ if (self->child_pid_all_ns_stopped1 == 0) {
+ pause();
+ _exit(EXIT_SUCCESS);
+ }
+
+ self->child_pid_all_ns_stopped2 = create_child(&self->child_pidfd_all_ns_stopped2,
+ CLONE_NEWUSER |
+ CLONE_NEWNS |
+ CLONE_NEWCGROUP |
+ CLONE_NEWIPC |
+ CLONE_NEWUTS |
+ CLONE_NEWPID |
+ CLONE_NEWNET);
+ ASSERT_GE(self->child_pid_all_ns_stopped2, 0);
+
+ if (self->child_pid_all_ns_stopped2 == 0) {
+ pause();
+ _exit(EXIT_SUCCESS);
+ }
+
+ for (i = 0; i < PIDFD_NS_MAX; i++) {
+ char path[100];
+
+ const struct ns_info *info = &ns_info[i];
+
+ self->ns_fds[i] = openat(proc_fd, info->proc_name, O_RDONLY | O_CLOEXEC);
+ if (self->ns_fds[i] < 0) {
+ EXPECT_EQ(errno, ENOENT) {
+ TH_LOG("%m - Failed to open %s namespace for process %d",
+ info->proc_name, self->pid);
+ }
+ }
+
+ (void)snprintf(path, sizeof(path), "/proc/%d/ns/%s", self->child_pid_all_ns_stopped1, info->proc_name);
+ self->child_ns_fds_all_ns_stopped1[i] = open(path, O_RDONLY | O_CLOEXEC);
+ if (self->child_ns_fds_all_ns_stopped1[i] < 0) {
+ EXPECT_EQ(errno, ENOENT) {
+ TH_LOG("%m - Failed to open %s namespace for process %d",
+ info->proc_name, self->child_pid_all_ns_stopped1);
+ }
+ }
+
+ (void)snprintf(path, sizeof(path), "/proc/%d/ns/%s", self->child_pid_all_ns_stopped1, info->proc_name);
+ self->child_ns_fds_all_ns_stopped2[i] = open(path, O_RDONLY | O_CLOEXEC);
+ if (self->child_ns_fds_all_ns_stopped2[i] < 0) {
+ EXPECT_EQ(errno, ENOENT) {
+ TH_LOG("%m - Failed to open %s namespace for process %d",
+ info->proc_name, self->child_pid_all_ns_stopped1);
+ }
+ }
+ }
+}
+
+FIXTURE_TEARDOWN(current_nsset)
+{
+ int i;
+
+ ASSERT_EQ(sys_pidfd_send_signal(self->child_pidfd_all_ns_stopped1,
+ SIGKILL, NULL, 0), 0);
+ ASSERT_EQ(sys_pidfd_send_signal(self->child_pidfd_all_ns_stopped2,
+ SIGKILL, NULL, 0), 0);
+
+ for (i = 0; i < PIDFD_NS_MAX; i++) {
+ if (self->ns_fds[i] >= 0)
+ close(self->ns_fds[i]);
+ if (self->child_ns_fds_all_ns_stopped1[i] >= 0)
+ close(self->child_ns_fds_all_ns_stopped1[i]);
+ if (self->child_ns_fds_all_ns_stopped2[i] >= 0)
+ close(self->child_ns_fds_all_ns_stopped2[i]);
+ }
+
+ EXPECT_EQ(0, close(self->child_pidfd_all_ns_stopped1));
+ EXPECT_EQ(0, close(self->child_pidfd_all_ns_stopped2));
+ ASSERT_EQ(sys_waitid(P_PID, self->child_pid_exited, WEXITED), 0);
+ ASSERT_EQ(sys_waitid(P_PID, self->child_pid_all_ns_stopped1, WEXITED), 0);
+ ASSERT_EQ(sys_waitid(P_PID, self->child_pid_all_ns_stopped2, WEXITED), 0);
+}
+
+int preserve_ns(const int pid, const char *ns)
+{
+ int ret;
+/* 5 /proc + 21 /int_as_str + 3 /ns + 20 /NS_NAME + 1 \0 */
+#define __NS_PATH_LEN 50
+ char path[__NS_PATH_LEN];
+
+ /* This way we can use this function to also check whether namespaces
+ * are supported by the kernel by passing in the NULL or the empty
+ * string.
+ */
+ ret = snprintf(path, __NS_PATH_LEN, "/proc/%d/ns%s%s", pid,
+ !ns || strcmp(ns, "") == 0 ? "" : "/",
+ !ns || strcmp(ns, "") == 0 ? "" : ns);
+ if (ret < 0 || (size_t)ret >= __NS_PATH_LEN) {
+ errno = EFBIG;
+ return -1;
+ }
+
+ return open(path, O_RDONLY | O_CLOEXEC);
+}
+
+static int in_same_namespace(int ns_fd1, pid_t pid2, const char *ns)
+{
+ int ns_fd2 = -EBADF;
+ int ret = -1;
+ struct stat ns_st1, ns_st2;
+
+ ret = fstat(ns_fd1, &ns_st1);
+ if (ret < 0)
+ return -1;
+
+ ns_fd2 = preserve_ns(pid2, ns);
+ if (ns_fd2 < 0)
+ return -1;
+
+ ret = fstat(ns_fd2, &ns_st2);
+ close(ns_fd2);
+ if (ret < 0)
+ return -1;
+
+ /* processes are in the same namespace */
+ if ((ns_st1.st_dev == ns_st2.st_dev) &&
+ (ns_st1.st_ino == ns_st2.st_ino))
+ return 1;
+
+ /* processes are in different namespaces */
+ return 0;
+}
+
+/* Test that we can't pass garbage to the kernel. */
+TEST_F(current_nsset, invalid_flags)
+{
+ ASSERT_NE(setns(self->pidfd, 0), 0);
+ EXPECT_EQ(errno, EINVAL);
+
+ ASSERT_NE(setns(self->pidfd, -1), 0);
+ EXPECT_EQ(errno, EINVAL);
+
+ ASSERT_NE(setns(self->pidfd, CLONE_VM), 0);
+ EXPECT_EQ(errno, EINVAL);
+
+ ASSERT_NE(setns(self->pidfd, CLONE_NEWUSER | CLONE_VM), 0);
+ EXPECT_EQ(errno, EINVAL);
+}
+
+/* Test that we can't attach to a task that has already exited. */
+TEST_F(current_nsset, exited_child)
+{
+ int i;
+ pid_t pid;
+
+ ASSERT_NE(setns(self->child_pidfd_exited, CLONE_NEWUSER | CLONE_NEWNET), 0);
+ EXPECT_EQ(errno, ESRCH);
+
+ pid = getpid();
+ for (i = 0; i < PIDFD_NS_MAX; i++) {
+ const struct ns_info *info = &ns_info[i];
+ /* Verify that we haven't changed any namespaces. */
+ if (self->ns_fds[i] >= 0)
+ ASSERT_EQ(in_same_namespace(self->ns_fds[i], pid, info->proc_name), 1);
+ }
+}
+
+TEST_F(current_nsset, incremental_setns)
+{
+ int i;
+ pid_t pid;
+
+ pid = getpid();
+ for (i = 0; i < PIDFD_NS_MAX; i++) {
+ const struct ns_info *info = &ns_info[i];
+ int nsfd;
+
+ if (self->child_ns_fds_all_ns_stopped1[i] < 0)
+ continue;
+
+ if (info->clone_flag) {
+ ASSERT_EQ(setns(self->child_pidfd_all_ns_stopped1, info->clone_flag), 0) {
+ TH_LOG("%m - Failed to setns to %s namespace of %d", info->proc_name, self->child_pid_all_ns_stopped1);
+ }
+ }
+
+ /* Verify that we have changed to the correct namespaces. */
+ if (info->clone_flag == CLONE_NEWPID)
+ nsfd = self->ns_fds[i];
+ else
+ nsfd = self->child_ns_fds_all_ns_stopped1[i];
+ ASSERT_EQ(in_same_namespace(nsfd, pid, info->proc_name), 1) {
+ TH_LOG("setns failed to place us correctly into %s namespace of %d", info->proc_name, self->child_pid_all_ns_stopped1);
+ }
+ TH_LOG("Managed to correctly setns to %s namespace of %d", info->proc_name, self->child_pid_all_ns_stopped1);
+ }
+}
+
+TEST_F(current_nsset, one_shot_setns)
+{
+ unsigned flags = 0;
+ int i;
+ pid_t pid;
+
+ for (i = 0; i < PIDFD_NS_MAX; i++) {
+ const struct ns_info *info = &ns_info[i];
+
+ if (self->child_ns_fds_all_ns_stopped1[i] < 0)
+ continue;
+
+ flags |= info->clone_flag;
+ TH_LOG("Adding %s namespace of %d to list of namespaces to attach to", info->proc_name, self->child_pid_all_ns_stopped1);
+ }
+
+ ASSERT_EQ(setns(self->child_pidfd_all_ns_stopped1, flags), 0) {
+ TH_LOG("%m - Failed to setns to namespaces of %d", self->child_pid_all_ns_stopped1);
+ }
+
+ pid = getpid();
+ for (i = 0; i < PIDFD_NS_MAX; i++) {
+ const struct ns_info *info = &ns_info[i];
+ int nsfd;
+
+ if (self->child_ns_fds_all_ns_stopped1[i] < 0)
+ continue;
+
+ /* Verify that we have changed to the correct namespaces. */
+ if (info->clone_flag == CLONE_NEWPID)
+ nsfd = self->ns_fds[i];
+ else
+ nsfd = self->child_ns_fds_all_ns_stopped1[i];
+ ASSERT_EQ(in_same_namespace(nsfd, pid, info->proc_name), 1) {
+ TH_LOG("setns failed to place us correctly into %s namespace of %d", info->proc_name, self->child_pid_all_ns_stopped1);
+ }
+ TH_LOG("Managed to correctly setns to %s namespace of %d", info->proc_name, self->child_pid_all_ns_stopped1);
+ }
+}
+
+TEST_F(current_nsset, no_foul_play)
+{
+ unsigned flags = 0;
+ int i;
+
+ for (i = 0; i < PIDFD_NS_MAX; i++) {
+ const struct ns_info *info = &ns_info[i];
+
+ if (self->child_ns_fds_all_ns_stopped1[i] < 0)
+ continue;
+
+ flags |= info->clone_flag;
+ if (info->clone_flag) /* No use logging pid_for_children. */
+ TH_LOG("Adding %s namespace of %d to list of namespaces to attach to", info->proc_name, self->child_pid_all_ns_stopped1);
+ }
+
+ ASSERT_EQ(setns(self->child_pidfd_all_ns_stopped1, flags), 0) {
+ TH_LOG("%m - Failed to setns to namespaces of %d", self->child_pid_all_ns_stopped1);
+ }
+
+
+ /*
+ * Can't setns to a user namespace outside of our hierarchy since we
+ * don't have caps in there and didn't create it. That means that under
+ * no circumstances should we be able to setns to any of the other
+ * ones since they aren't owned by our user namespace.
+ */
+ for (i = 0; i < PIDFD_NS_MAX; i++) {
+ const struct ns_info *info = &ns_info[i];
+
+ if (self->child_ns_fds_all_ns_stopped1[i] < 0)
+ continue;
+
+ if (!info->clone_flag)
+ continue;
+
+ ASSERT_NE(setns(self->child_pidfd_all_ns_stopped2, info->clone_flag), 0) {
+ TH_LOG("Managed to setns to %s namespace of %d", info->proc_name, self->child_pid_all_ns_stopped2);
+ }
+ TH_LOG("%m - Correctly failed to setns to %s namespace of %d", info->proc_name, self->child_pid_all_ns_stopped2);
+ }
+}
+
+TEST_HARNESS_MAIN
--
2.26.2

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