source4/smbd/pidfile.c

   1 /* this code is broken - there is a race condition with the unlink (tridge) */
   2
   3 /*
   4    Unix SMB/CIFS implementation.
   5    pidfile handling
   6    Copyright (C) Andrew Tridgell 1998
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20 */
  21
  22 #include "includes.h"
  23 #include "system/filesys.h"
  24 #include "smbd/pidfile.h"
  25
  26 /**
  27  * @file
  28  * @brief Pid file handling
  29  */
  30
  31 /**
  32  * return the pid in a pidfile. return 0 if the process (or pidfile)
  33  * does not exist
  34  */
  35 pid_t pidfile_pid(const char *piddir, const char *name)
  36 {
  37         int fd;
  38         char pidstr[20];
  39         pid_t ret;
  40         char *pidFile;
  41
  42         if (asprintf(&pidFile, "%s/%s.pid", piddir, name) < 0) {
  43                 return 0;
  44         }
  45
  46         fd = open(pidFile, O_NONBLOCK | O_RDONLY, 0644);
  47
  48         if (fd == -1) {
  49                 SAFE_FREE(pidFile);
  50                 return 0;
  51         }
  52
  53         ZERO_STRUCT(pidstr);
  54
  55         if (read(fd, pidstr, sizeof(pidstr)-1) <= 0) {
  56                 goto noproc;
  57         }
  58
  59         ret = (pid_t)atoi(pidstr);
  60         if (ret <= 0) {
  61                 goto noproc;
  62         }
  63
  64         if (!process_exists_by_pid(ret)) {
  65                 goto noproc;
  66         }
  67
  68         if (fcntl_lock(fd,F_SETLK,0,1,F_RDLCK)) {
  69                 /* we could get the lock - it can't be a Samba process */
  70                 goto noproc;
  71         }
  72
  73         close(fd);
  74         SAFE_FREE(pidFile);
  75         return ret;
  76
  77  noproc:
  78         close(fd);
  79         unlink(pidFile);
  80         SAFE_FREE(pidFile);
  81         return 0;
  82 }
  83
  84 /**
  85  * create a pid file in the pid directory. open it and leave it locked
  86  */
  87 void pidfile_create(const char *piddir, const char *name)
  88 {
  89         int     fd;
  90         char    buf[20];
  91         char *pidFile;
  92         pid_t pid;
  93
  94         if (asprintf(&pidFile, "%s/%s.pid", piddir, name) < 0) {
  95                 DEBUG(0,("ERROR: Out of memory\n"));
  96                 exit(1);
  97         }
  98
  99         pid = pidfile_pid(piddir, name);
 100         if (pid != 0) {
 101                 DEBUG(0,("ERROR: %s is already running. File %s exists and process id %d is running.\n",
 102                          name, pidFile, (int)pid));
 103                 exit(1);
 104         }
 105
 106         fd = open(pidFile, O_NONBLOCK | O_CREAT | O_WRONLY | O_EXCL, 0644);
 107         if (fd == -1) {
 108                 DEBUG(0,("ERROR: can't open %s: Error was %s\n", pidFile,
 109                          strerror(errno)));
 110                 exit(1);
 111         }
 112
 113         smb_set_close_on_exec(fd);
 114
 115         if (fcntl_lock(fd,F_SETLK,0,1,F_WRLCK)==false) {
 116                 DEBUG(0,("ERROR: %s : fcntl lock of file %s failed. Error was %s\n",
 117               name, pidFile, strerror(errno)));
 118                 exit(1);
 119         }
 120
 121         memset(buf, 0, sizeof(buf));
 122         slprintf(buf, sizeof(buf) - 1, "%u\n", (unsigned int) getpid());
 123         if (write(fd, buf, strlen(buf)) != (ssize_t)strlen(buf)) {
 124                 DEBUG(0,("ERROR: can't write to file %s: %s\n",
 125                          pidFile, strerror(errno)));
 126                 exit(1);
 127         }
 128
 129         /* Leave pid file open & locked for the duration... */
 130         SAFE_FREE(pidFile);
 131 }