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linux/tools/testing/selftests/pid_namespace/pid_max.c
Peter Seiderer 11f6dcf784 selftests: pid_namespace: add missing sys/mount.h include in pid_max.c 
Fix compile on openSUSE Tumbleweed (gcc-14.2.1, glibc-2.40):
  - add missing sys/mount.h include

Fixes:

  pid_max.c: In function ‘pid_max_cb’:
  pid_max.c:42:15: error: implicit declaration of function ‘mount’ [-Wimplicit-function-declaration]
     42 |         ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
        |               ^~~~~

Link: https://lore.kernel.org/r/20250115105211.390370-3-ps.report@gmx.net
Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Reviewed-by: T.J. Mercier <tjmercier@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
2025-05-09 13:12:33 -06:00

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/* SPDX-License-Identifier: GPL-2.0 */
#define _GNU_SOURCE
#include <assert.h>
#include <errno.h>
#include <fcntl.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/mount.h>
#include <sys/wait.h>
#include "../kselftest_harness.h"
#include "../pidfd/pidfd.h"
#define __STACK_SIZE (8 * 1024 * 1024)
static pid_t do_clone(int (*fn)(void *), void *arg, int flags)
{
char *stack;
pid_t ret;
stack = malloc(__STACK_SIZE);
if (!stack)
return -ENOMEM;
#ifdef __ia64__
ret = __clone2(fn, stack, __STACK_SIZE, flags | SIGCHLD, arg);
#else
ret = clone(fn, stack + __STACK_SIZE, flags | SIGCHLD, arg);
#endif
free(stack);
return ret;
}
static int pid_max_cb(void *data)
{
int fd, ret;
pid_t pid;
ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
if (ret) {
fprintf(stderr, "%m - Failed to make rootfs private mount\n");
return -1;
}
umount2("/proc", MNT_DETACH);
ret = mount("proc", "/proc", "proc", 0, NULL);
if (ret) {
fprintf(stderr, "%m - Failed to mount proc\n");
return -1;
}
fd = open("/proc/sys/kernel/pid_max", O_RDWR | O_CLOEXEC | O_NOCTTY);
if (fd < 0) {
fprintf(stderr, "%m - Failed to open pid_max\n");
return -1;
}
ret = write(fd, "500", sizeof("500") - 1);
if (ret < 0) {
fprintf(stderr, "%m - Failed to write pid_max\n");
return -1;
}
for (int i = 0; i < 501; i++) {
pid = fork();
if (pid == 0)
exit(EXIT_SUCCESS);
wait_for_pid(pid);
if (pid > 500) {
fprintf(stderr, "Managed to create pid number beyond limit\n");
return -1;
}
}
return 0;
}
static int pid_max_nested_inner(void *data)
{
int fret = -1;
pid_t pids[2];
int fd, i, ret;
ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
if (ret) {
fprintf(stderr, "%m - Failed to make rootfs private mount\n");
return fret;
}
umount2("/proc", MNT_DETACH);
ret = mount("proc", "/proc", "proc", 0, NULL);
if (ret) {
fprintf(stderr, "%m - Failed to mount proc\n");
return fret;
}
fd = open("/proc/sys/kernel/pid_max", O_RDWR | O_CLOEXEC | O_NOCTTY);
if (fd < 0) {
fprintf(stderr, "%m - Failed to open pid_max\n");
return fret;
}
ret = write(fd, "500", sizeof("500") - 1);
close(fd);
if (ret < 0) {
fprintf(stderr, "%m - Failed to write pid_max\n");
return fret;
}
pids[0] = fork();
if (pids[0] < 0) {
fprintf(stderr, "Failed to create first new process\n");
return fret;
}
if (pids[0] == 0)
exit(EXIT_SUCCESS);
pids[1] = fork();
wait_for_pid(pids[0]);
if (pids[1] >= 0) {
if (pids[1] == 0)
exit(EXIT_SUCCESS);
wait_for_pid(pids[1]);
fprintf(stderr, "Managed to create process even though ancestor pid namespace had a limit\n");
return fret;
}
/* Now make sure that we wrap pids at 400. */
for (i = 0; i < 510; i++) {
pid_t pid;
pid = fork();
if (pid < 0)
return fret;
if (pid == 0)
exit(EXIT_SUCCESS);
wait_for_pid(pid);
if (pid >= 500) {
fprintf(stderr, "Managed to create process with pid %d beyond configured limit\n", pid);
return fret;
}
}
return 0;
}
static int pid_max_nested_outer(void *data)
{
int fret = -1, nr_procs = 400;
pid_t pids[1000];
int fd, i, ret;
pid_t pid;
ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
if (ret) {
fprintf(stderr, "%m - Failed to make rootfs private mount\n");
return fret;
}
umount2("/proc", MNT_DETACH);
ret = mount("proc", "/proc", "proc", 0, NULL);
if (ret) {
fprintf(stderr, "%m - Failed to mount proc\n");
return fret;
}
fd = open("/proc/sys/kernel/pid_max", O_RDWR | O_CLOEXEC | O_NOCTTY);
if (fd < 0) {
fprintf(stderr, "%m - Failed to open pid_max\n");
return fret;
}
ret = write(fd, "400", sizeof("400") - 1);
close(fd);
if (ret < 0) {
fprintf(stderr, "%m - Failed to write pid_max\n");
return fret;
}
/*
* Create 397 processes. This leaves room for do_clone() (398) and
* one more 399. So creating another process needs to fail.
*/
for (nr_procs = 0; nr_procs < 396; nr_procs++) {
pid = fork();
if (pid < 0)
goto reap;
if (pid == 0)
exit(EXIT_SUCCESS);
pids[nr_procs] = pid;
}
pid = do_clone(pid_max_nested_inner, NULL, CLONE_NEWPID | CLONE_NEWNS);
if (pid < 0) {
fprintf(stderr, "%m - Failed to clone nested pidns\n");
goto reap;
}
if (wait_for_pid(pid)) {
fprintf(stderr, "%m - Nested pid_max failed\n");
goto reap;
}
fret = 0;
reap:
for (int i = 0; i < nr_procs; i++)
wait_for_pid(pids[i]);
return fret;
}
static int pid_max_nested_limit_inner(void *data)
{
int fret = -1, nr_procs = 400;
int fd, ret;
pid_t pid;
pid_t pids[1000];
ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
if (ret) {
fprintf(stderr, "%m - Failed to make rootfs private mount\n");
return fret;
}
umount2("/proc", MNT_DETACH);
ret = mount("proc", "/proc", "proc", 0, NULL);
if (ret) {
fprintf(stderr, "%m - Failed to mount proc\n");
return fret;
}
fd = open("/proc/sys/kernel/pid_max", O_RDWR | O_CLOEXEC | O_NOCTTY);
if (fd < 0) {
fprintf(stderr, "%m - Failed to open pid_max\n");
return fret;
}
ret = write(fd, "500", sizeof("500") - 1);
close(fd);
if (ret < 0) {
fprintf(stderr, "%m - Failed to write pid_max\n");
return fret;
}
for (nr_procs = 0; nr_procs < 500; nr_procs++) {
pid = fork();
if (pid < 0)
break;
if (pid == 0)
exit(EXIT_SUCCESS);
pids[nr_procs] = pid;
}
if (nr_procs >= 400) {
fprintf(stderr, "Managed to create processes beyond the configured outer limit\n");
goto reap;
}
fret = 0;
reap:
for (int i = 0; i < nr_procs; i++)
wait_for_pid(pids[i]);
return fret;
}
static int pid_max_nested_limit_outer(void *data)
{
int fd, ret;
pid_t pid;
ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
if (ret) {
fprintf(stderr, "%m - Failed to make rootfs private mount\n");
return -1;
}
umount2("/proc", MNT_DETACH);
ret = mount("proc", "/proc", "proc", 0, NULL);
if (ret) {
fprintf(stderr, "%m - Failed to mount proc\n");
return -1;
}
fd = open("/proc/sys/kernel/pid_max", O_RDWR | O_CLOEXEC | O_NOCTTY);
if (fd < 0) {
fprintf(stderr, "%m - Failed to open pid_max\n");
return -1;
}
ret = write(fd, "400", sizeof("400") - 1);
close(fd);
if (ret < 0) {
fprintf(stderr, "%m - Failed to write pid_max\n");
return -1;
}
pid = do_clone(pid_max_nested_limit_inner, NULL, CLONE_NEWPID | CLONE_NEWNS);
if (pid < 0) {
fprintf(stderr, "%m - Failed to clone nested pidns\n");
return -1;
}
if (wait_for_pid(pid)) {
fprintf(stderr, "%m - Nested pid_max failed\n");
return -1;
}
return 0;
}
TEST(pid_max_simple)
{
pid_t pid;
pid = do_clone(pid_max_cb, NULL, CLONE_NEWPID | CLONE_NEWNS);
ASSERT_GT(pid, 0);
ASSERT_EQ(0, wait_for_pid(pid));
}
TEST(pid_max_nested_limit)
{
pid_t pid;
pid = do_clone(pid_max_nested_limit_outer, NULL, CLONE_NEWPID | CLONE_NEWNS);
ASSERT_GT(pid, 0);
ASSERT_EQ(0, wait_for_pid(pid));
}
TEST(pid_max_nested)
{
pid_t pid;
pid = do_clone(pid_max_nested_outer, NULL, CLONE_NEWPID | CLONE_NEWNS);
ASSERT_GT(pid, 0);
ASSERT_EQ(0, wait_for_pid(pid));
}
TEST_HARNESS_MAIN
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