1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2026 ConnectWise 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25 * SUCH DAMAGE. 26 */ 27 28 #include <sys/types.h> 29 #include <sys/user.h> 30 #include <sys/proc.h> 31 #include <sys/procdesc.h> 32 #include <sys/sysctl.h> 33 #include <sys/wait.h> 34 35 #include <atf-c.h> 36 #include <stdio.h> 37 38 /* Tests for procdesc(4) that aren't specific to any one syscall */ 39 40 /* 41 * Even after waiting on a process descriptor with waitpid(2), the kernel will 42 * not recycle the pid until after the process descriptor is closed. That is 43 * important to prevent users from trying to wait() twice, the second time 44 * using a dangling pid. 45 * 46 * Whether this same anti-recycling behavior is used with pdwait() is 47 * unimportant, because pdwait _always_ uses a process descriptor. 48 */ 49 ATF_TC_WITHOUT_HEAD(pid_recycle); 50 ATF_TC_BODY(pid_recycle, tc) 51 { 52 size_t len; 53 int i, pd, pid_max; 54 pid_t dangle_pid; 55 56 len = sizeof(pid_max); 57 ATF_REQUIRE_EQ_MSG(0, 58 sysctlbyname("kern.pid_max", &pid_max, &len, NULL, 0), 59 "sysctlbyname: %s", strerror(errno)); 60 61 /* Create a process descriptor */ 62 dangle_pid = pdfork(&pd, PD_CLOEXEC | PD_DAEMON); 63 ATF_REQUIRE_MSG(dangle_pid >= 0, "pdfork: %s", strerror(errno)); 64 if (dangle_pid == 0) { 65 // In child 66 _exit(0); 67 } 68 /* 69 * Reap the child, but don't close the pd, creating a dangling pid. 70 * Notably, it isn't a Zombie, because the process is reaped. 71 */ 72 ATF_REQUIRE_EQ(dangle_pid, waitpid(dangle_pid, NULL, WEXITED)); 73 74 /* 75 * Now create and kill pid_max additional children. Test to see if pid 76 * gets reused. If not, that means the kernel is correctly reserving 77 * the dangling pid from reuse. 78 */ 79 for (i = 0; i < pid_max; i++) { 80 pid_t pid; 81 82 pid = vfork(); 83 ATF_REQUIRE_MSG(pid >= 0, "vfork: %s", strerror(errno)); 84 if (pid == 0) 85 _exit(0); 86 ATF_REQUIRE_MSG(pid != dangle_pid, 87 "pid got recycled after %d forks", i); 88 ATF_REQUIRE_EQ(pid, waitpid(pid, NULL, WEXITED)); 89 } 90 close(pd); 91 } 92 93 ATF_TP_ADD_TCS(tp) 94 { 95 ATF_TP_ADD_TC(tp, pid_recycle); 96 97 return (atf_no_error()); 98 } 99