[PATCH v8 2/2] selftests: add tests for clone3()

[Adrian Reber]

This tests clone3() with *set_tid to see if all desired PIDs are working
as expected. The tests are trying multiple invalid input parameters as
well as creating processes while specifying a certain PID in multiple
PID namespaces at the same time.

Signed-off-by: Adrian Reber <areber@xxxxxxxxxx>
---
 tools/testing/selftests/clone3/.gitignore     |   1 +
 tools/testing/selftests/clone3/Makefile       |   2 +-
 .../testing/selftests/clone3/clone3_set_tid.c | 345 ++++++++++++++++++
 3 files changed, 347 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/clone3/clone3_set_tid.c

diff --git a/tools/testing/selftests/clone3/.gitignore b/tools/testing/selftests/clone3/.gitignore
index 85d9d3ba2524..d56c3c49d869 100644
--- a/tools/testing/selftests/clone3/.gitignore
+++ b/tools/testing/selftests/clone3/.gitignore
@@ -1 +1,2 @@
 clone3
+clone3_set_tid
diff --git a/tools/testing/selftests/clone3/Makefile b/tools/testing/selftests/clone3/Makefile
index ea922c014ae4..2d292545ca8e 100644
--- a/tools/testing/selftests/clone3/Makefile
+++ b/tools/testing/selftests/clone3/Makefile
@@ -2,6 +2,6 @@
 
 CFLAGS += -I../../../../usr/include/
 
-TEST_GEN_PROGS := clone3
+TEST_GEN_PROGS := clone3 clone3_set_tid
 
 include ../lib.mk
diff --git a/tools/testing/selftests/clone3/clone3_set_tid.c b/tools/testing/selftests/clone3/clone3_set_tid.c
new file mode 100644
index 000000000000..9a234fd2031e
--- /dev/null
+++ b/tools/testing/selftests/clone3/clone3_set_tid.c
@@ -0,0 +1,345 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Based on Christian Brauner's clone3() example.
+ * These tests are assuming to be running in the host's
+ * PID namespace.
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <sched.h>
+
+#include "../kselftest.h"
+
+#ifndef MAX_PID_NS_LEVEL
+#define MAX_PID_NS_LEVEL 32
+#endif
+
+static int pipe_1[2];
+static int pipe_2[2];
+
+static pid_t raw_clone(struct clone_args *args)
+{
+	return syscall(__NR_clone3, args, sizeof(struct clone_args));
+}
+
+static int call_clone3_set_tid(pid_t *set_tid,
+			       size_t set_tid_size,
+			       int flags,
+			       int expected_pid,
+			       int wait_for_it)
+{
+	int status;
+	int ret = 0;
+	pid_t pid = -1;
+	struct clone_args args = {0};
+
+	args.flags = flags;
+	args.exit_signal = SIGCHLD;
+	args.set_tid = (__u64)set_tid;
+	args.set_tid_size = set_tid_size;
+
+	pid = raw_clone(&args);
+	if (pid < 0) {
+		ksft_print_msg("%s - Failed to create new process\n",
+			       strerror(errno));
+		return -errno;
+	}
+
+	if (pid == 0) {
+		char tmp = 0;
+		ksft_print_msg("I am the child, my PID is %d (expected %d)\n",
+			       getpid(), set_tid[0]);
+		if (wait_for_it) {
+			ksft_print_msg("[%d] Child is ready and waiting\n", getpid());
+			/* Signal the parent that the child is ready */
+			close(pipe_1[0]);
+			write(pipe_1[1], &tmp, 1);
+			close(pipe_1[1]);
+			close(pipe_2[1]);
+			read(pipe_2[0], &tmp, 1);
+			close(pipe_2[0]);
+		}
+
+		if (set_tid[0] != getpid())
+			_exit(EXIT_FAILURE);
+		_exit(EXIT_SUCCESS);
+	}
+
+	if (expected_pid == 0 || expected_pid == pid)
+		ksft_print_msg("I am the parent (%d). My child's pid is %d\n",
+			       getpid(), pid);
+	else {
+		ksft_print_msg(
+			"Expected child pid %d does not match actual pid %d\n",
+			expected_pid, pid);
+		ret = -1;
+	}
+
+	if (wait(&status) < 0) {
+		ksft_print_msg("Child returned %s\n", strerror(errno));
+		return -errno;
+	}
+	if (WEXITSTATUS(status))
+		return WEXITSTATUS(status);
+
+	return ret;
+}
+
+static void test_clone3_set_tid(pid_t *set_tid,
+				size_t set_tid_size,
+				int flags,
+				int expected,
+				int expected_pid,
+				int wait_for_it)
+{
+	int ret;
+
+	ksft_print_msg(
+		"[%d] Trying clone3() with CLONE_SET_TID to %d and 0x%x\n",
+		getpid(), set_tid[0], flags);
+	ret = call_clone3_set_tid(set_tid, set_tid_size, flags, expected_pid,
+				  wait_for_it);
+	ksft_print_msg(
+		"[%d] clone3() with CLONE_SET_TID %d says :%d - expected %d\n",
+		getpid(), set_tid[0], ret, expected);
+	if (ret != expected)
+		ksft_test_result_fail(
+			"[%d] Result (%d) is different than expected (%d)\n",
+			getpid(), ret, expected);
+	else
+		ksft_test_result_pass("[%d] Result (%d) matches expectation (%d)\n",
+			getpid(), ret, expected);
+}
+int main(int argc, char *argv[])
+{
+	FILE *f;
+	char buf;
+	pid_t pid;
+	pid_t ns1;
+	pid_t ns2;
+	pid_t ns3;
+	int status;
+	char *proc;
+	int ret = -1;
+	pid_t ns_pid;
+	int pid_max = 0;
+	uid_t uid = getuid();
+	char line[1024] = {0};
+	pid_t set_tid[MAX_PID_NS_LEVEL * 2];
+	pid_t set_tid_small[1];
+
+	if (pipe(pipe_1) == -1 || pipe(pipe_2))
+		 ksft_exit_fail_msg("pipe() failed\n");
+
+	ksft_print_header();
+	ksft_set_plan(27);
+
+	f = fopen("/proc/sys/kernel/pid_max", "r");
+	if (f == NULL)
+		ksft_exit_fail_msg(
+			"%s - Could not open /proc/sys/kernel/pid_max\n",
+			strerror(errno));
+	fscanf(f, "%d", &pid_max);
+	fclose(f);
+	ksft_print_msg("/proc/sys/kernel/pid_max %d\n", pid_max);
+
+	/* Try invalid settings */
+	memset(&set_tid, 0, sizeof(set_tid));
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL + 1, 0, -E2BIG, 0, 0);
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2, 0, -E2BIG, 0, 0);
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2 + 1, 0, -E2BIG, 0, 0);
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 42, 0, -E2BIG, 0, 0);
+
+	/* small set_tid array, but maximum set_tid_size */
+	/* Find the current active PID */
+	pid = fork();
+	if (pid == 0) {
+		ksft_print_msg("Child has PID %d\n", getpid());
+		_exit(EXIT_SUCCESS);
+	}
+	(void)wait(NULL);
+	/* After the child has finished, its PID should be free. */
+	set_tid_small[0] = pid;
+	/*
+	 * There is a chance that this can return -EFAULT as the actual
+	 * set_tid array has only one entry, but we are telling the kernel
+	 * that it has the size MAX_PID_NS_LEVEL. This could lead to a
+	 * situation where copy_from_user() fails. So far it always
+	 * succeeds and copies random data (whatever is after set_tid_small).
+	 */
+	test_clone3_set_tid(set_tid_small, MAX_PID_NS_LEVEL, 0, -EINVAL, 0, 0);
+
+	/*
+	 * This can actually work if this test running in a MAX_PID_NS_LEVEL - 1
+	 * nested PID namespace.
+	 */
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL - 1, 0, -EINVAL, 0, 0);
+
+	memset(&set_tid, 0xff, sizeof(set_tid));
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL + 1, 0, -E2BIG, 0, 0);
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2, 0, -E2BIG, 0, 0);
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2 + 1, 0, -E2BIG, 0, 0);
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 42, 0, -E2BIG, 0, 0);
+	/*
+	 * This can actually work if this test running in a MAX_PID_NS_LEVEL - 1
+	 * nested PID namespace.
+	 */
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL - 1, 0, -EINVAL, 0, 0);
+
+	memset(&set_tid, 0, sizeof(set_tid));
+	/* Try with an invalid PID */
+	set_tid[0] = 0;
+	test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
+	set_tid[0] = -1;
+	test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
+	/* Claim that the set_tid array actually contains 2 elements. */
+	test_clone3_set_tid(set_tid, 2, 0, -EINVAL, 0, 0);
+	/* Try it in a new PID namespace */
+	if (uid == 0)
+		test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EINVAL, 0, 0);
+	else
+		test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EPERM, 0, 0);
+
+	/*
+	 * Try with a valid PID (1) but as non-root. This should fail
+	 * with -EPERM if running in the initial user namespace.
+	 * As root it should tell us -EEXIST.
+	 */
+	set_tid[0] = 1;
+	if (uid == 0)
+		test_clone3_set_tid(set_tid, 1, 0, -EEXIST, 0, 0);
+	else
+		test_clone3_set_tid(set_tid, 1, 0, -EPERM, 0, 0);
+
+	/* Try it in a new PID namespace */
+	if (uid == 0)
+		test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, 0, 0, 0);
+	else
+		test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EPERM, 0, 0);
+
+	/* pid_max should fail everywhere */
+	set_tid[0] = pid_max;
+	test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
+	if (uid == 0)
+		test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EINVAL, 0, 0);
+	else
+		test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EPERM, 0, 0);
+
+	if (uid != 0) {
+		/*
+		 * All remaining tests require root. Tell the framework
+		 * that all those tests are skipped as non-root.
+		 */
+		ksft_cnt.ksft_xskip += ksft_plan - ksft_test_num();
+		goto out;
+	}
+
+	/* Find the current active PID */
+	pid = fork();
+	if (pid == 0) {
+		ksft_print_msg("Child has PID %d\n", getpid());
+		usleep(500);
+		_exit(EXIT_SUCCESS);
+	}
+	(void)wait(NULL);
+	/* After the child has finished, its PID should be free. */
+	set_tid[0] = pid;
+	test_clone3_set_tid(set_tid, 1, 0, 0, 0, 0);
+	/* This should fail as there is no PID 1 in that namespace */
+	test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EINVAL, 0, 0);
+	set_tid[0] = 1;
+	set_tid[1] = pid;
+	test_clone3_set_tid(set_tid, 2, CLONE_NEWPID, 0, pid, 0);
+
+	ksft_print_msg("unshare PID namespace\n");
+	unshare(CLONE_NEWPID);
+	set_tid[0] = pid;
+	/* This should fail as there is no PID 1 in that namespace */
+	test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
+
+	/* Let's create a PID 1 */
+	ns_pid = fork();
+	if (ns_pid == 0) {
+		ksft_print_msg("Child in PID namespace has PID %d\n", getpid());
+		set_tid[0] = 2;
+		test_clone3_set_tid(set_tid, 1, 0, 0, 2, 0);
+		set_tid[0] = 1;
+		set_tid[1] = 42;
+		set_tid[2] = pid;
+		/*
+		 * This should fail as there are not enough active PID
+		 * namespaces. Again assuming this is running in the host's
+		 * PID namespace. Not yet nested.
+		 */
+		test_clone3_set_tid(set_tid, 4, CLONE_NEWPID, -EINVAL, 0, 0);
+		/*
+		 * This should work and from the parent we should see
+		 * something like 'NSpid:	pid	42	1'.
+		 */
+		test_clone3_set_tid(set_tid, 3, CLONE_NEWPID, 0, 42, 1);
+		_exit(ksft_cnt.ksft_pass);
+	}
+
+	close(pipe_1[1]);
+	close(pipe_2[0]);
+	while (read(pipe_1[0], &buf, 1) > 0) {
+		ksft_print_msg("[%d] Child is ready and waiting\n", getpid());
+		break;
+	}
+
+	asprintf(&proc, "/proc/%d/status", pid);
+	f = fopen(proc, "r");
+	if (f == NULL)
+		ksft_exit_fail_msg(
+			"%s - Could not open %s\n",
+			strerror(errno), proc);
+	while (fgets(line, 1024, f)) {
+		if (strstr(line, "NSpid")) {
+			/* Verify that all generated PIDs are as expected. */
+			sscanf(line, "NSpid:\t%d\t%d\t%d", &ns3, &ns2, &ns1);
+			break;
+		}
+	}
+	fclose(f);
+	free(proc);
+	close(pipe_2[0]);
+	/* Tell the clone3()'d child to finish. */
+	write(pipe_2[1], &buf, 1);
+	close(pipe_2[1]);
+
+	if (wait(&status) < 0) {
+		ksft_print_msg("Child returned %s\n", strerror(errno));
+		ret = -errno;
+		goto out;
+	}
+	if (WEXITSTATUS(status))
+		/*
+		 * Update the number of total tests with the tests from the
+		 * child processes.
+		 */
+		ksft_cnt.ksft_pass = WEXITSTATUS(status);
+
+	if (ns3 == pid && ns2 == 42 && ns1 == 1)
+		ksft_test_result_pass(
+			"PIDs in all namespaces as expected (%d,%d,%d)\n",
+			ns3, ns2, ns1);
+	else
+		ksft_test_result_fail(
+			"PIDs in all namespaces not as expected (%d,%d,%d)\n",
+			ns3, ns2, ns1);
+out:
+	ret = 0;
+
+	return !ret ? ksft_exit_pass() : ksft_exit_fail();
+}
-- 
2.23.0