// 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