The branch main has been updated by asomers: URL: https://cgit.FreeBSD.org/src/commit/?id=e35df41f68916cc23893a29e0284f386ec727462
commit e35df41f68916cc23893a29e0284f386ec727462 Author: Alan Somers <[email protected]> AuthorDate: 2026-01-13 00:45:23 +0000 Commit: Alan Somers <[email protected]> CommitDate: 2026-01-26 14:36:57 +0000 procdesc: Add a test for pid recycling behavior MFC With: 09984871d8caff9263b955a94bb9fb5354af1b4c Sponsored by: ConnectWise --- tests/sys/kern/Makefile | 1 + tests/sys/kern/procdesc.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 99 insertions(+) diff --git a/tests/sys/kern/Makefile b/tests/sys/kern/Makefile index e56dd560414a..b3611f34996d 100644 --- a/tests/sys/kern/Makefile +++ b/tests/sys/kern/Makefile @@ -30,6 +30,7 @@ ATF_TESTS_C+= ktrace_test ATF_TESTS_C+= listener_wakeup ATF_TESTS_C+= module_test ATF_TESTS_C+= prace +ATF_TESTS_C+= procdesc ATF_TESTS_C+= ptrace_test TEST_METADATA.ptrace_test+= timeout="15" ATF_TESTS_C+= reaper diff --git a/tests/sys/kern/procdesc.c b/tests/sys/kern/procdesc.c new file mode 100644 index 000000000000..3334ee404518 --- /dev/null +++ b/tests/sys/kern/procdesc.c @@ -0,0 +1,98 @@ +/*- + * SPDX-License-Identifier: BSD-2-Clause + * + * Copyright (c) 2026 ConnectWise + * + * 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 AUTHOR 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 AUTHOR 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/types.h> +#include <sys/user.h> +#include <sys/proc.h> +#include <sys/procdesc.h> +#include <sys/sysctl.h> +#include <sys/wait.h> + +#include <atf-c.h> +#include <stdio.h> + +/* Tests for procdesc(4) that aren't specific to any one syscall */ + +/* + * Even after waiting on a process descriptor with waitpid(2), the kernel will + * not recycle the pid until after the process descriptor is closed. That is + * important to prevent users from trying to wait() twice, the second time + * using a dangling pid. + * + * Whether this same anti-recycling behavior is used with pdwait() is + * unimportant, because pdwait _always_ uses a process descriptor. + */ +ATF_TC_WITHOUT_HEAD(pid_recycle); +ATF_TC_BODY(pid_recycle, tc) +{ + size_t len; + int i, pd, pid_max; + pid_t dangle_pid; + + len = sizeof(pid_max); + ATF_REQUIRE_EQ_MSG(0, + sysctlbyname("kern.pid_max", &pid_max, &len, NULL, 0), + "sysctlbyname: %s", strerror(errno)); + + /* Create a process descriptor */ + dangle_pid = pdfork(&pd, PD_CLOEXEC | PD_DAEMON); + ATF_REQUIRE_MSG(dangle_pid >= 0, "pdfork: %s", strerror(errno)); + if (dangle_pid == 0) { + // In child + _exit(0); + } + /* + * Reap the child, but don't close the pd, creating a dangling pid. + * Notably, it isn't a Zombie, because the process is reaped. + */ + ATF_REQUIRE_EQ(dangle_pid, waitpid(dangle_pid, NULL, WEXITED)); + + /* + * Now create and kill pid_max additional children. Test to see if pid + * gets reused. If not, that means the kernel is correctly reserving + * the dangling pid from reuse. + */ + for (i = 0; i < pid_max; i++) { + pid_t pid; + + pid = vfork(); + ATF_REQUIRE_MSG(pid >= 0, "vfork: %s", strerror(errno)); + if (pid == 0) + _exit(0); + ATF_REQUIRE_MSG(pid != dangle_pid, + "pid got recycled after %d forks", i); + ATF_REQUIRE_EQ(pid, waitpid(pid, NULL, WEXITED)); + } + close(pd); +} + +ATF_TP_ADD_TCS(tp) +{ + ATF_TP_ADD_TC(tp, pid_recycle); + + return (atf_no_error()); +}
