libc/sys/t_setrlimit.c

/* $NetBSD: t_setrlimit.c,v 1.7.10.1 2023/11/28 12:56:27 martin Exp $ */

/*-
 * Copyright (c) 2011 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jukka Ruohonen.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
#include <sys/cdefs.h>
__RCSID("$NetBSD: t_setrlimit.c,v 1.7.10.1 2023/11/28 12:56:27 martin Exp $");

#include <sys/resource.h>
#include <sys/mman.h>
#include <sys/wait.h>

#include <atf-c.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <lwp.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ucontext.h>
#include <unistd.h>

#include "h_macros.h"

static void		 sighandler(int);
static const char	 path[] = "setrlimit";

static const int rlimit[] = {
	RLIMIT_AS,
	RLIMIT_CORE,
	RLIMIT_CPU,
	RLIMIT_DATA,
	RLIMIT_FSIZE,
	RLIMIT_MEMLOCK,
	RLIMIT_NOFILE,
	RLIMIT_NPROC,
	RLIMIT_RSS,
	RLIMIT_SBSIZE,
	RLIMIT_STACK
};

ATF_TC(setrlimit_basic);
ATF_TC_HEAD(setrlimit_basic, tc)
{
	atf_tc_set_md_var(tc, "descr", "A basic soft limit test");
}

ATF_TC_BODY(setrlimit_basic, tc)
{
	struct rlimit res;
	int *buf, lim;
	size_t i;

	buf = calloc(__arraycount(rlimit), sizeof(int));

	if (buf == NULL)
		atf_tc_fail("initialization failed");

	for (i = lim = 0; i < __arraycount(rlimit); i++) {

		(void)memset(&res, 0, sizeof(struct rlimit));

		if (getrlimit(rlimit[i], &res) != 0)
			continue;

		if (res.rlim_cur == RLIM_INFINITY || res.rlim_cur == 0)
			continue;

		if (res.rlim_cur == res.rlim_max) /* An unprivileged run. */
			continue;

		buf[i] = res.rlim_cur;
		res.rlim_cur = res.rlim_cur - 1;

		if (setrlimit(rlimit[i], &res) != 0) {
			lim = rlimit[i];
			goto out;
		}
	}

out:
	for (i = 0; i < __arraycount(rlimit); i++) {

		(void)memset(&res, 0, sizeof(struct rlimit));

		if (buf[i] == 0)
			continue;

		if (getrlimit(rlimit[i], &res) != 0)
			continue;

		res.rlim_cur = buf[i];

		(void)setrlimit(rlimit[i], &res);
	}

	if (lim != 0)
		atf_tc_fail("failed to set limit (%d)", lim);
	free(buf);
}

ATF_TC(setrlimit_current);
ATF_TC_HEAD(setrlimit_current, tc)
{
	atf_tc_set_md_var(tc, "descr", "setrlimit(3) with current limits");
}

ATF_TC_BODY(setrlimit_current, tc)
{
	struct rlimit res;
	size_t i;

	for (i = 0; i < __arraycount(rlimit); i++) {

		(void)memset(&res, 0, sizeof(struct rlimit));

		ATF_REQUIRE(getrlimit(rlimit[i], &res) == 0);
		ATF_REQUIRE(setrlimit(rlimit[i], &res) == 0);
	}
}

ATF_TC(setrlimit_err);
ATF_TC_HEAD(setrlimit_err, tc)
{
	atf_tc_set_md_var(tc, "descr", "Test error conditions");
}

ATF_TC_BODY(setrlimit_err, tc)
{
	struct rlimit res;
	size_t i;

	for (i = 0; i < __arraycount(rlimit); i++) {

		errno = 0;

		ATF_REQUIRE(getrlimit(rlimit[i], (void *)0) != 0);
		ATF_REQUIRE(errno == EFAULT);
	}

	errno = 0;

	ATF_REQUIRE(getrlimit(INT_MAX, &res) != 0);
	ATF_REQUIRE(errno == EINVAL);
}

ATF_TC_WITH_CLEANUP(setrlimit_fsize);
ATF_TC_HEAD(setrlimit_fsize, tc)
{
	atf_tc_set_md_var(tc, "descr", "Test setrlimit(2), RLIMIT_FSIZE");
}

ATF_TC_BODY(setrlimit_fsize, tc)
{
	struct rlimit res;
	int fd, sta;
	pid_t pid;

	fd = open(path, O_RDWR | O_CREAT, 0700);

	if (fd < 0)
		atf_tc_fail("initialization failed");

	pid = fork();
	ATF_REQUIRE(pid >= 0);

	if (pid == 0) {

		res.rlim_cur = 2;
		res.rlim_max = 2;

		if (setrlimit(RLIMIT_FSIZE, &res) != 0)
			_exit(EXIT_FAILURE);

		if (signal(SIGXFSZ, sighandler) == SIG_ERR)
			_exit(EXIT_FAILURE);

		/*
		 * The third call should generate a SIGXFSZ.
		 */
		(void)write(fd, "X", 1);
		(void)write(fd, "X", 1);
		(void)write(fd, "X", 1);

		_exit(EXIT_FAILURE);
	}

	(void)close(fd);
	(void)wait(&sta);
	(void)unlink(path);

	if (WIFEXITED(sta) == 0 || WEXITSTATUS(sta) != EXIT_SUCCESS)
		atf_tc_fail("RLIMIT_FSIZE not enforced");
}

ATF_TC_CLEANUP(setrlimit_fsize, tc)
{
	(void)unlink(path);
}

static void
sighandler(int signo)
{

	if (signo != SIGXFSZ)
		_exit(EXIT_FAILURE);

	_exit(EXIT_SUCCESS);
}

ATF_TC(setrlimit_memlock);
ATF_TC_HEAD(setrlimit_memlock, tc)
{
	atf_tc_set_md_var(tc, "descr", "Test setrlimit(2), RLIMIT_MEMLOCK");
}

ATF_TC_BODY(setrlimit_memlock, tc)
{
	struct rlimit res;
	void *buf;
	long page;
	pid_t pid;
	int sta;

	page = sysconf(_SC_PAGESIZE);
	ATF_REQUIRE(page >= 0);

	buf = malloc(page);
	pid = fork();

	if (buf == NULL || pid < 0)
		atf_tc_fail("initialization failed");

	if (pid == 0) {

		/*
		 * Try to lock a page while
		 * RLIMIT_MEMLOCK is zero.
		 */
		if (mlock(buf, page) != 0)
			_exit(EXIT_FAILURE);

		if (munlock(buf, page) != 0)
			_exit(EXIT_FAILURE);

		res.rlim_cur = 0;
		res.rlim_max = 0;

		if (setrlimit(RLIMIT_MEMLOCK, &res) != 0)
			_exit(EXIT_FAILURE);

		if (mlock(buf, page) != 0)
			_exit(EXIT_SUCCESS);

		(void)munlock(buf, page);

		_exit(EXIT_FAILURE);
	}

	free(buf);

	(void)wait(&sta);

	if (WIFEXITED(sta) == 0 || WEXITSTATUS(sta) != EXIT_SUCCESS)
		atf_tc_fail("RLIMIT_MEMLOCK not enforced");
}

ATF_TC(setrlimit_nofile_1);
ATF_TC_HEAD(setrlimit_nofile_1, tc)
{
	atf_tc_set_md_var(tc, "descr", "Test setrlimit(2), RLIMIT_NOFILE, #1");
}

ATF_TC_BODY(setrlimit_nofile_1, tc)
{
	struct rlimit res;
	int fd, i, rv, sta;
	pid_t pid;

	res.rlim_cur = 0;
	res.rlim_max = 0;

	pid = fork();
	ATF_REQUIRE(pid >= 0);

	if (pid == 0) {

		/*
		 * Close all descriptors, set RLIMIT_NOFILE
		 * to zero, and try to open a random file.
		 * This should fail with EMFILE.
		 */
		for (i = 0; i < 1024; i++)
			(void)close(i);

		rv = setrlimit(RLIMIT_NOFILE, &res);

		if (rv != 0)
			_exit(EXIT_FAILURE);

		errno = 0;
		fd = open("/etc/passwd", O_RDONLY);

		if (fd >= 0 || errno != EMFILE)
			_exit(EXIT_FAILURE);

		_exit(EXIT_SUCCESS);
	}

	(void)wait(&sta);

	if (WIFEXITED(sta) == 0 || WEXITSTATUS(sta) != EXIT_SUCCESS)
		atf_tc_fail("RLIMIT_NOFILE not enforced");
}

ATF_TC(setrlimit_nofile_2);
ATF_TC_HEAD(setrlimit_nofile_2, tc)
{
	atf_tc_set_md_var(tc, "descr", "Test setrlimit(2), RLIMIT_NOFILE, #2");
}

ATF_TC_BODY(setrlimit_nofile_2, tc)
{
	static const rlim_t lim = 12;
	struct rlimit res;
	int fd, i, rv, sta;
	pid_t pid;

	/*
	 * See that an arbitrary limit on
	 * open files is being enforced.
	 */
	res.rlim_cur = lim;
	res.rlim_max = lim;

	pid = fork();
	ATF_REQUIRE(pid >= 0);

	if (pid == 0) {

		for (i = 0; i < 1024; i++)
			(void)close(i);

		rv = setrlimit(RLIMIT_NOFILE, &res);

		if (rv != 0)
			_exit(EXIT_FAILURE);

		for (i = 0; i < (int)lim; i++) {

			fd = open("/etc/passwd", O_RDONLY);

			if (fd < 0)
				_exit(EXIT_FAILURE);
		}

		/*
		 * After the limit has been reached,
		 * EMFILE should again follow.
		 */
		fd = open("/etc/passwd", O_RDONLY);

		if (fd >= 0 || errno != EMFILE)
			_exit(EXIT_FAILURE);

		_exit(EXIT_SUCCESS);
	}

	(void)wait(&sta);

	if (WIFEXITED(sta) == 0 || WEXITSTATUS(sta) != EXIT_SUCCESS)
		atf_tc_fail("RLIMIT_NOFILE not enforced");
}

ATF_TC(setrlimit_nproc);
ATF_TC_HEAD(setrlimit_nproc, tc)
{
	atf_tc_set_md_var(tc, "descr", "Test setrlimit(2), RLIMIT_NPROC");
	atf_tc_set_md_var(tc, "require.user", "unprivileged");
}

ATF_TC_BODY(setrlimit_nproc, tc)
{
	struct rlimit res;
	pid_t pid, cpid;
	int sta;

	pid = fork();
	ATF_REQUIRE(pid >= 0);

	if (pid == 0) {

		/*
		 * Set RLIMIT_NPROC to zero and try to fork.
		 */
		res.rlim_cur = 0;
		res.rlim_max = 0;

		if (setrlimit(RLIMIT_NPROC, &res) != 0)
			_exit(EXIT_FAILURE);

		cpid = fork();

		if (cpid < 0)
			_exit(EXIT_SUCCESS);

		_exit(EXIT_FAILURE);
	}

	(void)waitpid(pid, &sta, 0);

	if (WIFEXITED(sta) == 0 || WEXITSTATUS(sta) != EXIT_SUCCESS)
		atf_tc_fail("RLIMIT_NPROC not enforced");
}

ATF_TC(setrlimit_nthr);
ATF_TC_HEAD(setrlimit_nthr, tc)
{
	atf_tc_set_md_var(tc, "descr", "Test setrlimit(2), RLIMIT_NTHR");
	atf_tc_set_md_var(tc, "require.user", "unprivileged");
}

static void
func(lwpid_t *id)
{
	printf("thread %d\n", *id);
	fflush(stdout);
	_lwp_exit();
}

ATF_TC_BODY(setrlimit_nthr, tc)
{
	struct rlimit res;
	lwpid_t lwpid;
	ucontext_t c;

	/*
	 * Set RLIMIT_NTHR to zero and try to create a thread.
	 */
	res.rlim_cur = 0;
	res.rlim_max = 0;
	ATF_REQUIRE(setrlimit(RLIMIT_NTHR, &res) == 0);
	ATF_REQUIRE(getcontext(&c) == 0);
	c.uc_link = NULL;
	sigemptyset(&c.uc_sigmask);
	c.uc_stack.ss_flags = 0;
	c.uc_stack.ss_size = 4096;
	ATF_REQUIRE((c.uc_stack.ss_sp = malloc(c.uc_stack.ss_size)) != NULL);
	makecontext(&c, func, 1, &lwpid);
	ATF_CHECK_ERRNO(EAGAIN, _lwp_create(&c, 0, &lwpid) == -1);
}

ATF_TC(setrlimit_perm);
ATF_TC_HEAD(setrlimit_perm, tc)
{
	atf_tc_set_md_var(tc, "descr", "Test setrlimit(2) for EPERM");
	atf_tc_set_md_var(tc, "require.user", "unprivileged");
}

ATF_TC_BODY(setrlimit_perm, tc)
{
	struct rlimit res;
	size_t i;

	/*
	 * Try to raise the maximum limits as an user.
	 */
	for (i = 0; i < __arraycount(rlimit); i++) {

		ATF_REQUIRE(getrlimit(rlimit[i], &res) == 0);

		if (res.rlim_max == UINT64_MAX) /* Overflow. */
			continue;

		errno = 0;
		res.rlim_max = res.rlim_max + 1;

		ATF_CHECK_ERRNO(EPERM, setrlimit(rlimit[i], &res) != 0);
	}
}

ATF_TC(setrlimit_stack);
ATF_TC_HEAD(setrlimit_stack, tc)
{
	atf_tc_set_md_var(tc, "descr", "Test setrlimit(2), RLIMIT_STACK");
	atf_tc_set_md_var(tc, "require.user", "unprivileged");
}

ATF_TC_BODY(setrlimit_stack, tc)
{
	struct rlimit res;

	/* Ensure soft limit is not bigger than hard limit */
	res.rlim_cur = res.rlim_max = 6 * 1024 * 1024;
	ATF_REQUIRE(setrlimit(RLIMIT_STACK, &res) == 0);
	ATF_REQUIRE(getrlimit(RLIMIT_STACK, &res) == 0);
	ATF_CHECK(res.rlim_cur <= res.rlim_max);

}

ATF_TC(setrlimit_stack_growshrink);
ATF_TC_HEAD(setrlimit_stack_growshrink, tc)
{
	atf_tc_set_md_var(tc, "descr",
	    "Test that setrlimit(2), RLIMIT_STACK, grows & shrinks the stack");
}

/*
 * checkstack(n, ok)
 *
 *	Check whether we can allocate an array of size n on the stack.
 *
 *	- If expectsegv, verify that access fails with SIGSEGV.
 *	- If not expectsegv, verify that access succeeds.
 *
 *	Do this in a subprocess rather than with a SIGSEGV handler,
 *	because once we've allocated an array of size n on the stack,
 *	in the case where the stack is inaccessible, we have just
 *	trashed the stack pointer so badly we can't make function calls
 *	like to a SIGSEGV handler.
 *
 *	(We could use an alternate signal stack, but I already wrote it
 *	this way, and this is a little simpler and more robust than
 *	juggling signals, setjmp/longjmp, and sigaltstack.)
 */
static void
checkstack(size_t n, int expectsegv)
{
	pid_t forked, waited;
	size_t i;
	int status;

	RL(forked = fork());
	if (forked == 0) {	/* child */
		volatile char *const x = alloca(n);
		for (i = 0; i < n; i++)
			x[i] = 0x1a;
		_exit(expectsegv);
	}

	/* parent */
	RL(waited = waitpid(forked, &status, 0));
	ATF_REQUIRE_EQ_MSG(waited, forked, "waited=%jd forked=%jd",
	    (intmax_t)waited, (intmax_t)forked);
	if (expectsegv) {
		ATF_REQUIRE_MSG(!WIFEXITED(status),
		    "expected signal but exited normally with status %d",
		    WEXITSTATUS(status));
		ATF_REQUIRE_MSG(WIFSIGNALED(status), "status=0x%x", status);
		ATF_REQUIRE_EQ_MSG(WTERMSIG(status), SIGSEGV, "termsig=%d",
		    WTERMSIG(status));
	} else {
		ATF_REQUIRE_MSG(!WIFSIGNALED(status),
		    "expected normal exit but termintaed on signal %d",
		    WTERMSIG(status));
		ATF_REQUIRE_MSG(WIFEXITED(status), "status=0x%x", status);
		ATF_REQUIRE_EQ_MSG(WEXITSTATUS(status), 0, "exitstatus=%d",
		    WEXITSTATUS(status));
	}
}

ATF_TC_BODY(setrlimit_stack_growshrink, tc)
{
	struct rlimit res;
	size_t n;

	/*
	 * Disable core dumps -- we're going to deliberately cause
	 * SIGSEGV to test stack accessibility (which breaks even
	 * calling a function so we can't just use a SIGSEGV handler),
	 * so let's not waste time dumping core.
	 */
	res = (struct rlimit){ .rlim_cur = 0, .rlim_max = 0 };
	RL(setrlimit(RLIMIT_CORE, &res));

	/*
	 * Get the current stack size and hard limit.
	 */
	RL(getrlimit(RLIMIT_STACK, &res));
	n = res.rlim_cur;

	/*
	 * Verify that we can't get at pages past the end of the stack
	 * right now.
	 */
	checkstack(n, /*expectsegv*/1);

	/*
	 * Stop if the hard limit is too small to test.  Not sure
	 * exactly how much more space we need to verify that setrlimit
	 * actually expands the stack without examining the current
	 * stack pointer relative to the process's stack base, so we'll
	 * just double the stack size -- definitely enough to test
	 * stack growth -- and hope the hard rlimit is big enough to
	 * let us double it.
	 */
	if (n > res.rlim_max/2)
		atf_tc_skip("hard stack rlimit is too small");

	/*
	 * Double the stack size.  This way we can allocate an array of
	 * length equal to the current stack size and be guaranteed
	 * that (a) it can be allocated, and (b) access to it requires
	 * the stack to have grown.
	 */
	res.rlim_cur = 2*n;
	RL(setrlimit(RLIMIT_STACK, &res));

	/*
	 * Verify that we can now get at pages past the end of the new
	 * stack but not beyond that.
	 */
	checkstack(n, /*expectsegv*/0);
	if (n < SIZE_MAX/2)
		checkstack(2*n, /*expectsegv*/1);

	/*
	 * Restore the stack size and verify that we can no longer
	 * access an array of length equal to the whole stack size.
	 */
	res.rlim_cur = n;
	RL(setrlimit(RLIMIT_STACK, &res));
	checkstack(n, /*expectsegv*/1);
}

ATF_TP_ADD_TCS(tp)
{

	ATF_TP_ADD_TC(tp, setrlimit_basic);
	ATF_TP_ADD_TC(tp, setrlimit_current);
	ATF_TP_ADD_TC(tp, setrlimit_err);
	ATF_TP_ADD_TC(tp, setrlimit_fsize);
	ATF_TP_ADD_TC(tp, setrlimit_memlock);
	ATF_TP_ADD_TC(tp, setrlimit_nofile_1);
	ATF_TP_ADD_TC(tp, setrlimit_nofile_2);
	ATF_TP_ADD_TC(tp, setrlimit_nproc);
	ATF_TP_ADD_TC(tp, setrlimit_perm);
	ATF_TP_ADD_TC(tp, setrlimit_nthr);
	ATF_TP_ADD_TC(tp, setrlimit_stack);
	ATF_TP_ADD_TC(tp, setrlimit_stack_growshrink);

	return atf_no_error();
}