selftests: add tests for clone3() with *set_tid

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.

Additionally this moves common clone3() test code into clone3_selftests.h.

Signed-off-by: Adrian Reber <[e-mail]>
Acked-by: Christian Brauner <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Christian Brauner <[e-mail]>

tools/testing/selftests/clone3/.gitignore

···
 clone3
 clone3_clear_sighand
+clone3_set_tid

tools/testing/selftests/clone3/Makefile

···
 # SPDX-License-Identifier: GPL-2.0
 CFLAGS += -g -I../../../../usr/include/
 
-TEST_GEN_PROGS := clone3 clone3_clear_sighand
+TEST_GEN_PROGS := clone3 clone3_clear_sighand clone3_set_tid
 
 include ../lib.mk

tools/testing/selftests/clone3/clone3.c

···
 #include <sched.h>
 
 #include "../kselftest.h"
+#include "clone3_selftests.h"
 
 /*
  * Different sizes of struct clone_args
···
 	CLONE3_ARGS_INVAL_EXIT_SIGNAL_CSIG,
 	CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG,
 };
-
-static pid_t raw_clone(struct clone_args *args, size_t size)
-{
-	return syscall(__NR_clone3, args, size);
-}
 
 static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode)
 {
···
 
 	memcpy(&args_ext.args, &args, sizeof(struct clone_args));
 
-	pid = raw_clone((struct clone_args *)&args_ext, size);
+	pid = sys_clone3((struct clone_args *)&args_ext, size);
 	if (pid < 0) {
 		ksft_print_msg("%s - Failed to create new process\n",
 				strerror(errno));

tools/testing/selftests/clone3/clone3_clear_sighand.c

···
 #include <sys/wait.h>
 
 #include "../kselftest.h"
+#include "clone3_selftests.h"
 
 #ifndef CLONE_CLEAR_SIGHAND
 #define CLONE_CLEAR_SIGHAND 0x100000000ULL
 #endif
-
-#ifndef __NR_clone3
-#define __NR_clone3 -1
-struct clone_args {
-	__aligned_u64 flags;
-	__aligned_u64 pidfd;
-	__aligned_u64 child_tid;
-	__aligned_u64 parent_tid;
-	__aligned_u64 exit_signal;
-	__aligned_u64 stack;
-	__aligned_u64 stack_size;
-	__aligned_u64 tls;
-};
-#endif
-
-static pid_t sys_clone3(struct clone_args *args, size_t size)
-{
-	return syscall(__NR_clone3, args, size);
-}
 
 static void test_clone3_supported(void)
 {

tools/testing/selftests/clone3/clone3_selftests.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _CLONE3_SELFTESTS_H
+#define _CLONE3_SELFTESTS_H
+
+#define _GNU_SOURCE
+#include <sched.h>
+#include <stdint.h>
+#include <syscall.h>
+#include <linux/types.h>
+
+#define ptr_to_u64(ptr) ((__u64)((uintptr_t)(ptr)))
+
+#ifndef __NR_clone3
+#define __NR_clone3 -1
+struct clone_args {
+	__aligned_u64 flags;
+	__aligned_u64 pidfd;
+	__aligned_u64 child_tid;
+	__aligned_u64 parent_tid;
+	__aligned_u64 exit_signal;
+	__aligned_u64 stack;
+	__aligned_u64 stack_size;
+	__aligned_u64 tls;
+	__aligned_u64 set_tid;
+	__aligned_u64 set_tid_size;
+};
+#endif
+
+static pid_t sys_clone3(struct clone_args *args, size_t size)
+{
+	return syscall(__NR_clone3, args, size);
+}
+
+#endif /* _CLONE3_SELFTESTS_H */

tools/testing/selftests/clone3/clone3_set_tid.c

···
+// 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 <stdbool.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"
+#include "clone3_selftests.h"
+
+#ifndef MAX_PID_NS_LEVEL
+#define MAX_PID_NS_LEVEL 32
+#endif
+
+static int pipe_1[2];
+static int pipe_2[2];
+
+static int call_clone3_set_tid(pid_t *set_tid,
+			       size_t set_tid_size,
+			       int flags,
+			       int expected_pid,
+			       bool wait_for_it)
+{
+	int status;
+	pid_t pid = -1;
+
+	struct clone_args args = {
+		.flags = flags,
+		.exit_signal = SIGCHLD,
+		.set_tid = ptr_to_u64(set_tid),
+		.set_tid_size = set_tid_size,
+	};
+
+	pid = sys_clone3(&args, sizeof(struct clone_args));
+	if (pid < 0) {
+		ksft_print_msg("%s - Failed to create new process\n",
+			       strerror(errno));
+		return -errno;
+	}
+
+	if (pid == 0) {
+		int ret;
+		char tmp = 0;
+		int exit_code = EXIT_SUCCESS;
+
+		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]);
+			ret = write(pipe_1[1], &tmp, 1);
+			if (ret != 1) {
+				ksft_print_msg(
+					"Writing to pipe returned %d", ret);
+				exit_code = EXIT_FAILURE;
+			}
+			close(pipe_1[1]);
+			close(pipe_2[1]);
+			ret = read(pipe_2[0], &tmp, 1);
+			if (ret != 1) {
+				ksft_print_msg(
+					"Reading from pipe returned %d", ret);
+				exit_code = EXIT_FAILURE;
+			}
+			close(pipe_2[0]);
+		}
+
+		if (set_tid[0] != getpid())
+			_exit(EXIT_FAILURE);
+		_exit(exit_code);
+	}
+
+	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);
+		return -1;
+	}
+
+	if (waitpid(pid, &status, 0) < 0) {
+		ksft_print_msg("Child returned %s\n", strerror(errno));
+		return -errno;
+	}
+
+	if (!WIFEXITED(status))
+		return -1;
+
+	return WEXITSTATUS(status);
+}
+
+static void test_clone3_set_tid(pid_t *set_tid,
+				size_t set_tid_size,
+				int flags,
+				int expected,
+				int expected_pid,
+				bool 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;
+	char *line;
+	int status;
+	int ret = -1;
+	size_t len = 0;
+	int pid_max = 0;
+	uid_t uid = getuid();
+	char proc_path[100] = {0};
+	pid_t pid, ns1, ns2, ns3, ns_pid;
+	pid_t set_tid[MAX_PID_NS_LEVEL * 2];
+
+	if (pipe(pipe_1) < 0 || pipe(pipe_2) < 0)
+		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, -EINVAL, 0, 0);
+
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2, 0, -EINVAL, 0, 0);
+
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2 + 1, 0,
+			-EINVAL, 0, 0);
+
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 42, 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, -EINVAL, 0, 0);
+
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2, 0, -EINVAL, 0, 0);
+
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2 + 1, 0,
+			-EINVAL, 0, 0);
+
+	test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 42, 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, 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
+		ksft_test_result_skip("Clone3() with set_tid requires root\n");
+
+	/* Try with a valid PID (1) this should return -EEXIST. */
+	set_tid[0] = 1;
+	if (uid == 0)
+		test_clone3_set_tid(set_tid, 1, 0, -EEXIST, 0, 0);
+	else
+		ksft_test_result_skip("Clone3() with set_tid requires root\n");
+
+	/* Try it in a new PID namespace */
+	if (uid == 0)
+		test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, 0, 0, 0);
+	else
+		ksft_test_result_skip("Clone3() with set_tid requires root\n");
+
+	/* 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
+		ksft_test_result_skip("Clone3() with set_tid requires root\n");
+
+	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());
+		_exit(EXIT_SUCCESS);
+	}
+	if (waitpid(pid, &status, 0) < 0)
+		ksft_exit_fail_msg("Waiting for child %d failed", pid);
+
+	/* 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);
+
+	/*
+	 * Creating a process with PID 1 in the newly created most nested
+	 * PID namespace and PID 'pid' in the parent PID namespace. This
+	 * needs to work.
+	 */
+	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");
+	if (unshare(CLONE_NEWPID) == -1)
+		ksft_exit_fail_msg("unshare(CLONE_NEWPID) failed: %s\n",
+				strerror(errno));
+
+	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] = -1;
+		set_tid[2] = pid;
+		/* This should fail as there is invalid PID at level '1'. */
+		test_clone3_set_tid(set_tid, 3, CLONE_NEWPID, -EINVAL, 0, 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, true);
+
+		_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;
+	}
+
+	snprintf(proc_path, sizeof(proc_path), "/proc/%d/status", pid);
+	f = fopen(proc_path, "r");
+	if (f == NULL)
+		ksft_exit_fail_msg(
+			"%s - Could not open %s\n",
+			strerror(errno), proc_path);
+
+	while (getline(&line, &len, f) != -1) {
+		if (strstr(line, "NSpid")) {
+			int i;
+
+			/* Verify that all generated PIDs are as expected. */
+			i = sscanf(line, "NSpid:\t%d\t%d\t%d",
+				   &ns3, &ns2, &ns1);
+			if (i != 3) {
+				ksft_print_msg(
+					"Unexpected 'NSPid:' entry: %s",
+					line);
+				ns1 = ns2 = ns3 = 0;
+			}
+			break;
+		}
+	}
+	fclose(f);
+	free(line);
+	close(pipe_2[0]);
+
+	/* Tell the clone3()'d child to finish. */
+	write(pipe_2[1], &buf, 1);
+	close(pipe_2[1]);
+
+	if (waitpid(ns_pid, &status, 0) < 0) {
+		ksft_print_msg("Child returned %s\n", strerror(errno));
+		ret = -errno;
+		goto out;
+	}
+
+	if (!WIFEXITED(status))
+		ksft_test_result_fail("Child error\n");
+
+	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();
+}