| /* |
| * a race in pid generation that causes pids to be reused immediately |
| * |
| * From the mainline commit 5fdee8c4a5e1800489ce61963208f8cc55e42ea1: |
| * |
| * A program that repeatedly forks and waits is susceptible to having |
| * the same pid repeated, especially when it competes with another |
| * instance of the same program. This is really bad for bash |
| * implementation. Furthermore, many shell scripts assume that pid |
| * numbers will not be used for some length of time. |
| * |
| * Race Description: |
| * |
| * A B |
| * |
| * // pid == offset == n // pid == offset == n + 1 |
| * test_and_set_bit(offset, map->page) |
| * test_and_set_bit(offset, map->page); |
| * pid_ns->last_pid = pid; |
| * pid_ns->last_pid = pid; |
| * // pid == n + 1 is freed (wait()) |
| * |
| * // Next fork()... |
| * last = pid_ns->last_pid; // == n |
| * pid = last + 1; |
| * |
| * Copyright (C) 2010 Red Hat, Inc. |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of version 2 of the GNU General Public |
| * License as published by the Free Software Foundation. |
| * |
| * This program is distributed in the hope that it would be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. |
| * |
| * Further, this software is distributed without any warranty that it |
| * is free of the rightful claim of any third person regarding |
| * infringement or the like. Any license provided herein, whether |
| * implied or otherwise, applies only to this software file. Patent |
| * licenses, if any, provided herein do not apply to combinations of |
| * this program with other software, or any other product whatsoever. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write the Free Software |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
| * 02110-1301, USA. |
| */ |
| |
| #include <sys/types.h> |
| #include <sys/stat.h> |
| #include <sys/wait.h> |
| #include <fcntl.h> |
| #include <errno.h> |
| #include <unistd.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include "test.h" |
| #include "usctest.h" |
| |
| char *TCID = "fork13"; |
| int TST_TOTAL = 1; |
| |
| static unsigned long pid_max; |
| |
| #define PID_MAX_PATH "/proc/sys/kernel/pid_max" |
| #define PID_MAX 32768 |
| #define RETURN 256 |
| |
| static void setup(void); |
| static int pid_distance(pid_t first, pid_t second); |
| static void cleanup(void); |
| static void check(void); |
| |
| int main(int argc, char *argv[]) |
| { |
| /* message returned from parse_opts */ |
| const char *msg; |
| |
| msg = parse_opts(argc, argv, NULL, NULL); |
| if (msg != NULL) |
| tst_brkm(TBROK, NULL, "OPTION PARSING ERROR - %s", msg); |
| setup(); |
| check(); |
| cleanup(); |
| tst_exit(); |
| } |
| |
| static void check(void) |
| { |
| long lc; |
| pid_t last_pid = 0; |
| pid_t pid; |
| int child_exit_code, distance, reaped, status; |
| |
| for (lc = 0; TEST_LOOPING(lc); lc++) { |
| tst_count = 0; |
| child_exit_code = lc % RETURN; |
| switch (pid = fork()) { |
| case -1: |
| tst_brkm(TBROK | TERRNO, cleanup, "fork"); |
| case 0: |
| exit(child_exit_code); |
| default: |
| if (lc > 0) { |
| distance = pid_distance(last_pid, pid); |
| if (distance == 0) { |
| tst_resm(TFAIL, |
| "Unexpected pid sequence: " |
| "previous fork: pid=%d, " |
| "current fork: pid=%d for " |
| "iteration=%ld.", last_pid, |
| pid, lc); |
| return; |
| } |
| } |
| last_pid = pid; |
| |
| reaped = waitpid(pid, &status, 0); |
| if (reaped != pid) { |
| tst_resm(TFAIL, |
| "Wait return value: expected pid=%d, " |
| "got %d, iteration %ld.", pid, reaped, |
| lc); |
| return; |
| } else if (WEXITSTATUS(status) != child_exit_code) { |
| tst_resm(TFAIL, "Unexpected exit status %x, " |
| "iteration %ld.", WEXITSTATUS(status), |
| lc); |
| return; |
| } |
| } |
| } |
| tst_resm(TPASS, "%ld pids forked, all passed", lc); |
| } |
| |
| static void setup(void) |
| { |
| tst_require_root(NULL); |
| |
| tst_sig(FORK, DEF_HANDLER, cleanup); |
| TEST_PAUSE; |
| |
| /* Backup pid_max value. */ |
| SAFE_FILE_SCANF(NULL, PID_MAX_PATH, "%lu", &pid_max); |
| |
| SAFE_FILE_PRINTF(NULL, PID_MAX_PATH, "%d", PID_MAX); |
| } |
| |
| static void cleanup(void) |
| { |
| /* Restore pid_max value. */ |
| SAFE_FILE_PRINTF(NULL, PID_MAX_PATH, "%lu", pid_max); |
| |
| TEST_CLEANUP; |
| } |
| |
| /* The distance mod PIDMAX between two pids, where the first pid is |
| expected to be smaller than the second. */ |
| static int pid_distance(pid_t first, pid_t second) |
| { |
| return (second + PID_MAX - first) % PID_MAX; |
| } |