tools/testing/selftests/rlimits/rlimits-per-userns.c

Source file repositories/reference/linux-study-clean/tools/testing/selftests/rlimits/rlimits-per-userns.c

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/rlimits/rlimits-per-userns.c
Extension
.c
Size
3325 bytes
Lines
162
Domain
Support Tooling And Documentation
Bucket
tools
Inferred role
Support Tooling And Documentation: implementation source
Status
source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Author: Alexey Gladkov <gladkov.alexey@gmail.com>
 */
#define _GNU_SOURCE
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/prctl.h>
#include <sys/stat.h>

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sched.h>
#include <signal.h>
#include <limits.h>
#include <fcntl.h>
#include <errno.h>
#include <err.h>

#define NR_CHILDS 2

static char *service_prog;
static uid_t user   = 60000;
static uid_t group  = 60000;

static void setrlimit_nproc(rlim_t n)
{
	pid_t pid = getpid();
	struct rlimit limit = {
		.rlim_cur = n,
		.rlim_max = n
	};

	warnx("(pid=%d): Setting RLIMIT_NPROC=%ld", pid, n);

	if (setrlimit(RLIMIT_NPROC, &limit) < 0)
		err(EXIT_FAILURE, "(pid=%d): setrlimit(RLIMIT_NPROC)", pid);
}

static pid_t fork_child(void)
{
	pid_t pid = fork();

	if (pid < 0)
		err(EXIT_FAILURE, "fork");

	if (pid > 0)
		return pid;

	pid = getpid();

	warnx("(pid=%d): New process starting ...", pid);

	if (prctl(PR_SET_PDEATHSIG, SIGKILL) < 0)
		err(EXIT_FAILURE, "(pid=%d): prctl(PR_SET_PDEATHSIG)", pid);

	signal(SIGUSR1, SIG_DFL);

	warnx("(pid=%d): Changing to uid=%d, gid=%d", pid, user, group);

	if (setgid(group) < 0)
		err(EXIT_FAILURE, "(pid=%d): setgid(%d)", pid, group);
	if (setuid(user) < 0)
		err(EXIT_FAILURE, "(pid=%d): setuid(%d)", pid, user);

	warnx("(pid=%d): Service running ...", pid);

	warnx("(pid=%d): Unshare user namespace", pid);
	if (unshare(CLONE_NEWUSER) < 0)
		err(EXIT_FAILURE, "unshare(CLONE_NEWUSER)");

	char *const argv[] = { "service", NULL };
	char *const envp[] = { "I_AM_SERVICE=1", NULL };

	warnx("(pid=%d): Executing real service ...", pid);

	execve(service_prog, argv, envp);
	err(EXIT_FAILURE, "(pid=%d): execve", pid);
}

int main(int argc, char **argv)
{
	size_t i;
	pid_t child[NR_CHILDS];
	int wstatus[NR_CHILDS];
	int childs = NR_CHILDS;

Annotation

Implementation Notes