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From:   Adrian Reber <areber@redhat.com>
To:     Christian Brauner <christian@brauner.io>,
        Eric Biederman <ebiederm@xmission.com>,
        Pavel Emelianov <xemul@virtuozzo.com>,
        Jann Horn <jannh@google.com>, Oleg Nesterov <oleg@redhat.com>,
        Dmitry Safonov <0x7f454c46@gmail.com>
Cc:     linux-kernel@vger.kernel.org, Andrei Vagin <avagin@gmail.com>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Radostin Stoyanov <rstoyanov1@gmail.com>,
        Adrian Reber <areber@redhat.com>
Subject: [PATCH v2 2/2] selftests: add test for clone3() with set_tid
Date:   Wed, 31 Jul 2019 18:12:23 +0200
Message-Id: <20190731161223.2928-2-areber@redhat.com>
In-Reply-To: <20190731161223.2928-1-areber@redhat.com>
References: <20190731161223.2928-1-areber@redhat.com>
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Sender: linux-kernel-owner@vger.kernel.org
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This tests clone3() with set_tid to see if all desired PIDs are working
as expected. The test tries to clone3() with a set_tid of -1, 1,
pid_max, a PID which is already in use and an unused PID. The same
tests are also running in PID namespace.

Signed-off-by: Adrian Reber <areber@redhat.com>
---
 tools/testing/selftests/clone3/.gitignore     |   1 +
 tools/testing/selftests/clone3/Makefile       |  11 ++
 .../testing/selftests/clone3/clone3_set_tid.c | 148 ++++++++++++++++++
 3 files changed, 160 insertions(+)
 create mode 100644 tools/testing/selftests/clone3/.gitignore
 create mode 100644 tools/testing/selftests/clone3/Makefile
 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
new file mode 100644
index 000000000000..09ccea33016c
--- /dev/null
+++ b/tools/testing/selftests/clone3/.gitignore
@@ -0,0 +1 @@
+clone3_set_tid
diff --git a/tools/testing/selftests/clone3/Makefile b/tools/testing/selftests/clone3/Makefile
new file mode 100644
index 000000000000..45c77b50f367
--- /dev/null
+++ b/tools/testing/selftests/clone3/Makefile
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0
+uname_M := $(shell uname -m 2>/dev/null || echo not)
+ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/i386/)
+
+CFLAGS += -I../../../../usr/include/
+
+ifeq ($(ARCH),x86_64)
+	TEST_GEN_PROGS := clone3_set_tid
+endif
+
+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..1ed0845aa4c5
--- /dev/null
+++ b/tools/testing/selftests/clone3/clone3_set_tid.c
@@ -0,0 +1,148 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/* Based on Christian Brauner's clone3() example */
+
+#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"
+
+static pid_t raw_clone(struct clone_args *args)
+{
+	return syscall(__NR_clone3, args, sizeof(struct clone_args));
+}
+
+static int call_clone3_set_tid(int set_tid, int flags)
+{
+	struct clone_args args = {0};
+	pid_t ppid = -1;
+	pid_t pid = -1;
+	int status;
+
+	args.flags = flags | CLONE_SET_TID;
+	args.exit_signal = SIGCHLD;
+	args.set_tid = set_tid;
+
+	pid = raw_clone(&args);
+	if (pid < 0) {
+		ksft_print_msg("%s - Failed to create new process\n",
+				strerror(errno));
+		return -errno;
+	}
+
+	if (pid == 0) {
+		ksft_print_msg("I am the child, my PID is %d\n", getpid());
+		if (set_tid != getpid())
+			_exit(EXIT_FAILURE);
+		_exit(EXIT_SUCCESS);
+	}
+
+	ppid = getpid();
+	ksft_print_msg("I am the parent (%d). My child's pid is %d\n",
+			ppid, pid);
+
+	(void)wait(&status);
+	if (WEXITSTATUS(status))
+		return WEXITSTATUS(status);
+
+	return 0;
+}
+
+static int test_clone3_set_tid(int set_tid, int flags, int expected)
+{
+	int ret;
+	ksft_print_msg("[%d] Trying clone3() with CLONE_SET_TID to %d "
+		        "and 0x%x\n", getpid(), set_tid, flags);
+	ret = call_clone3_set_tid(set_tid, flags);
+	ksft_print_msg("[%d] clone3() with CLONE_SET_TID %d says :%d "
+			"- expected %d\n", getpid(), set_tid, ret, expected);
+	if (ret != expected)
+		ksft_exit_fail_msg("[%d] Result (%d) is different than "
+				    "expected (%d)\n", getpid(), ret, expected);
+	ksft_test_result_pass("[%d] Result (%d) matches expectation (%d)\n",
+			getpid(), ret, expected);
+	return 0;
+}
+int main(int argc, char *argv[])
+{
+	FILE *f;
+	int pid_max = 0;
+	pid_t pid;
+	pid_t ns_pid;
+	int ret = -1;
+
+	ksft_print_header();
+	ksft_set_plan(10);
+
+	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);
+
+	/* First try with an invalid PID */
+	if (test_clone3_set_tid(-1, 0, -EINVAL))
+		goto on_error;
+	if (test_clone3_set_tid(-1, CLONE_NEWPID, -EINVAL))
+		goto on_error;
+	/* Then with PID 1 */
+	if (test_clone3_set_tid(1, 0, -EAGAIN))
+		goto on_error;
+	/* PID 1 should not fail in a PID namespace */
+	if (test_clone3_set_tid(1, CLONE_NEWPID, 0))
+		goto on_error;
+	/* pid_max should fail everywhere */
+	if (test_clone3_set_tid(pid_max, 0, -EINVAL))
+		goto on_error;
+	if (test_clone3_set_tid(pid_max, CLONE_NEWPID, -EINVAL))
+		goto on_error;
+	/* Find the current active PID */
+	pid = fork();
+	if (pid == 0) {
+		ksft_print_msg("Child has PID %d\n", getpid());
+		sleep(1);
+		_exit(EXIT_SUCCESS);
+	}
+	/* Try to create a process with that PID should fail */
+	if (test_clone3_set_tid(pid, 0, -EAGAIN))
+		goto on_error;
+	(void)wait(NULL);
+	/* After the child has finished, try again with the same PID */
+	if (test_clone3_set_tid(pid, 0, 0))
+		goto on_error;
+	/* This should fail as there is no PID 1 in that namespace */
+	if (test_clone3_set_tid(pid, CLONE_NEWPID, -EINVAL))
+		goto on_error;
+	unshare(CLONE_NEWPID);
+	/* 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());
+		sleep(1);
+		_exit(EXIT_SUCCESS);
+	}
+	/*
+	 * Now, after the unshare() it should be possible to create a process
+	 * with another ID than 1 in the PID namespace.
+	 */
+	if (test_clone3_set_tid(2, 0, 0))
+		goto on_error;
+	(void)wait(NULL);
+
+	ret = 0;
+on_error:
+
+	return !ret ? ksft_exit_pass() : ksft_exit_fail();
+}
-- 
2.21.0