124 lines
3.0 KiB
C
124 lines
3.0 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2010 Red Hat, Inc.
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* Copyright (C) 2022 Cyril Hrubis <chrubis@suse.cz>
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*/
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/*\
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* [Description]
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*
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* A race in pid generation that causes pids to be reused immediately
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*
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* From the mainline commit 5fdee8c4a5e1800489ce61963208f8cc55e42ea1:
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*
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* A program that repeatedly forks and waits is susceptible to having
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* the same pid repeated, especially when it competes with another
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* instance of the same program. This is really bad for bash
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* implementation. Furthermore, many shell scripts assume that pid
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* numbers will not be used for some length of time.
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*
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* [Race Description]
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* ---------------------------------------------------------------------
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* A B
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*
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* // pid == offset == n // pid == offset == n + 1
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* test_and_set_bit(offset, map->page)
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* test_and_set_bit(offset, map->page);
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* pid_ns->last_pid = pid;
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* pid_ns->last_pid = pid;
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* // pid == n + 1 is freed (wait())
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*
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* // Next fork()...
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* last = pid_ns->last_pid; // == n
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* pid = last + 1;
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* ---------------------------------------------------------------------
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*/
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/wait.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include "tst_test.h"
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#define PID_MAX 32768
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#define PID_MAX_STR "32768"
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#define RETURN 256
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#define MAX_ITERATIONS 1000000
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/* The distance mod PIDMAX between two pids, where the first pid is
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expected to be smaller than the second. */
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static int pid_distance(pid_t first, pid_t second)
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{
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return (second + PID_MAX - first) % PID_MAX;
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}
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static void check(void)
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{
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pid_t prev_pid = 0;
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pid_t pid;
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int i, distance, reaped, status, retval;
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for (i = 0; i < MAX_ITERATIONS; i++) {
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retval = i % RETURN;
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pid = SAFE_FORK();
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if (!pid)
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exit(retval);
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if (prev_pid) {
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distance = pid_distance(prev_pid, pid);
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if (distance == 0) {
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tst_res(TFAIL,
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"Unexpected pid sequence: prev_pid=%i, pid=%i for iteration=%i",
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prev_pid, pid, i);
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return;
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}
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}
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prev_pid = pid;
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reaped = SAFE_WAITPID(pid, &status, 0);
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if (reaped != pid) {
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tst_res(TFAIL,
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"Wrong pid %i returned from waitpid() expected %i",
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reaped, pid);
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return;
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}
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if (WEXITSTATUS(status) != retval) {
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tst_res(TFAIL,
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"Wrong process exit value %i expected %i",
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WEXITSTATUS(status), retval);
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return;
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}
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if (!tst_remaining_runtime()) {
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tst_res(TINFO, "Runtime exhausted, exiting...");
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break;
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}
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}
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tst_res(TPASS, "%i pids forked, all passed", i);
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}
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static struct tst_test test = {
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.needs_root = 1,
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.forks_child = 1,
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.max_runtime = 600,
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.test_all = check,
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.save_restore = (const struct tst_path_val[]) {
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{"/proc/sys/kernel/pid_max", PID_MAX_STR, TST_SR_TBROK},
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{}
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},
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.tags = (const struct tst_tag[]) {
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{"linux-git", "5fdee8c4a5e1"},
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{}
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}
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};
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