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// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE
#include <errno.h>
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
#include "../pidfd/pidfd.h"
#include "../kselftest_harness.h"
/*
* Regression tests for the setns(pidfd) active reference counting bug.
*
* These tests are based on the reproducers that triggered the race condition
* fixed by commit 1c465d0518dc ("ns: handle setns(pidfd, ...) cleanly").
*
* The bug: When using setns() with a pidfd, if the target task exits between
* prepare_nsset() and commit_nsset(), the namespaces would become inactive.
* Then ns_ref_active_get() would increment from 0 without properly resurrecting
* the owner chain, causing active reference count underflows.
*/
/*
* Simple pidfd setns test using create_child()+unshare().
*
* Without the fix, this would trigger active refcount warnings when the
* parent exits after doing setns(pidfd) on a child that has already exited.
*/
TEST(simple_pidfd_setns)
{
pid_t child_pid;
int pidfd = -1;
int ret;
int sv[2];
char c;
/* Ignore SIGCHLD for autoreap */
ASSERT_NE(signal(SIGCHLD, SIG_IGN), SIG_ERR);
ASSERT_EQ(socketpair(AF_UNIX, SOCK_STREAM, 0, sv), 0);
/* Create a child process without namespaces initially */
child_pid = create_child(&pidfd, 0);
ASSERT_GE(child_pid, 0);
if (child_pid == 0) {
close(sv[0]);
if (unshare(CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWNET | CLONE_NEWUSER) < 0) {
close(sv[1]);
_exit(1);
}
/* Signal parent that namespaces are ready */
if (write_nointr(sv[1], "1", 1) < 0) {
close(sv[1]);
_exit(1);
}
close(sv[1]);
_exit(0);
}
ASSERT_GE(pidfd, 0);
EXPECT_EQ(close(sv[1]), 0);
ret = read_nointr(sv[0], &c, 1);
ASSERT_EQ(ret, 1);
EXPECT_EQ(close(sv[0]), 0);
/* Set to child's namespaces via pidfd */
ret = setns(pidfd, CLONE_NEWUTS | CLONE_NEWIPC);
TH_LOG("setns() returned %d", ret);
close(pidfd);
}
/*
* Simple pidfd setns test using create_child().
*
* This variation uses create_child() with namespace flags directly.
* Namespaces are created immediately at clone time.
*/
TEST(simple_pidfd_setns_clone)
{
pid_t child_pid;
int pidfd = -1;
int ret;
/* Ignore SIGCHLD for autoreap */
ASSERT_NE(signal(SIGCHLD, SIG_IGN), SIG_ERR);
/* Create a child process with new namespaces using create_child() */
child_pid = create_child(&pidfd, CLONE_NEWUSER | CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWNET);
ASSERT_GE(child_pid, 0);
if (child_pid == 0) {
/* Child: sleep for a while so parent can setns to us */
sleep(2);
_exit(0);
}
/* Parent: pidfd was already created by create_child() */
ASSERT_GE(pidfd, 0);
/* Set to child's namespaces via pidfd */
ret = setns(pidfd, CLONE_NEWUTS | CLONE_NEWIPC);
close(pidfd);
TH_LOG("setns() returned %d", ret);
}
TEST_HARNESS_MAIN
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