Message-Id: <20200430165717.1001605-4-christian.brauner@ubuntu.com>
Date:   Thu, 30 Apr 2020 18:57:17 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     linux-kernel@...r.kernel.org
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Stéphane Graber <stgraber@...ntu.com>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Serge Hallyn <serge@...lyn.com>, Jann Horn <jannh@...gle.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Aleksa Sarai <cyphar@...har.com>, linux-api@...r.kernel.org,
        Christian Brauner <christian.brauner@...ntu.com>
Subject: [PATCH v2 4/4] selftests/pidfd: add pidfd setns tests

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@...ntu.com>
---
/* 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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