src/core/killall.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright 2010 ProFUSION embedded systems
   6 ***/
   7
   8 #include <errno.h>
   9 #include <signal.h>
  10 #include <sys/wait.h>
  11 #include <unistd.h>
  12
  13 #include "alloc-util.h"
  14 #include "def.h"
  15 #include "dirent-util.h"
  16 #include "fd-util.h"
  17 #include "format-util.h"
  18 #include "killall.h"
  19 #include "parse-util.h"
  20 #include "process-util.h"
  21 #include "set.h"
  22 #include "string-util.h"
  23 #include "terminal-util.h"
  24 #include "util.h"
  25
  26 static bool ignore_proc(pid_t pid, bool warn_rootfs) {
  27         _cleanup_fclose_ FILE *f = NULL;
  28         char c;
  29         const char *p;
  30         size_t count;
  31         uid_t uid;
  32         int r;
  33
  34         /* We are PID 1, let's not commit suicide */
  35         if (pid == 1)
  36                 return true;
  37
  38         r = get_process_uid(pid, &uid);
  39         if (r < 0)
  40                 return true; /* not really, but better safe than sorry */
  41
  42         /* Non-root processes otherwise are always subject to be killed */
  43         if (uid != 0)
  44                 return false;
  45
  46         p = procfs_file_alloca(pid, "cmdline");
  47         f = fopen(p, "re");
  48         if (!f)
  49                 return true; /* not really, but has the desired effect */
  50
  51         count = fread(&c, 1, 1, f);
  52
  53         /* Kernel threads have an empty cmdline */
  54         if (count <= 0)
  55                 return true;
  56
  57         /* Processes with argv[0][0] = '@' we ignore from the killing spree.
  58          *
  59          * http://www.freedesktop.org/wiki/Software/systemd/RootStorageDaemons */
  60         if (c != '@')
  61                 return false;
  62
  63         if (warn_rootfs &&
  64             pid_from_same_root_fs(pid) == 0) {
  65
  66                 _cleanup_free_ char *comm = NULL;
  67
  68                 get_process_comm(pid, &comm);
  69
  70                 log_notice("Process " PID_FMT " (%s) has been marked to be excluded from killing. It is "
  71                            "running from the root file system, and thus likely to block re-mounting of the "
  72                            "root file system to read-only. Please consider moving it into an initrd file "
  73                            "system instead.", pid, strna(comm));
  74         }
  75
  76         return true;
  77 }
  78
  79 static void wait_for_children(Set *pids, sigset_t *mask, usec_t timeout) {
  80         usec_t until;
  81
  82         assert(mask);
  83
  84         if (set_isempty(pids))
  85                 return;
  86
  87         until = now(CLOCK_MONOTONIC) + timeout;
  88         for (;;) {
  89                 struct timespec ts;
  90                 int k;
  91                 usec_t n;
  92                 void *p;
  93                 Iterator i;
  94
  95                 /* First, let the kernel inform us about killed
  96                  * children. Most processes will probably be our
  97                  * children, but some are not (might be our
  98                  * grandchildren instead...). */
  99                 for (;;) {
 100                         pid_t pid;
 101
 102                         pid = waitpid(-1, NULL, WNOHANG);
 103                         if (pid == 0)
 104                                 break;
 105                         if (pid < 0) {
 106                                 if (errno == ECHILD)
 107                                         break;
 108
 109                                 log_error_errno(errno, "waitpid() failed: %m");
 110                                 return;
 111                         }
 112
 113                         (void) set_remove(pids, PID_TO_PTR(pid));
 114                 }
 115
 116                 /* Now explicitly check who might be remaining, who
 117                  * might not be our child. */
 118                 SET_FOREACH(p, pids, i) {
 119
 120                         /* kill(pid, 0) sends no signal, but it tells
 121                          * us whether the process still exists. */
 122                         if (kill(PTR_TO_PID(p), 0) == 0)
 123                                 continue;
 124
 125                         if (errno != ESRCH)
 126                                 continue;
 127
 128                         set_remove(pids, p);
 129                 }
 130
 131                 if (set_isempty(pids))
 132                         return;
 133
 134                 n = now(CLOCK_MONOTONIC);
 135                 if (n >= until)
 136                         return;
 137
 138                 timespec_store(&ts, until - n);
 139                 k = sigtimedwait(mask, NULL, &ts);
 140                 if (k != SIGCHLD) {
 141
 142                         if (k < 0 && errno != EAGAIN) {
 143                                 log_error_errno(errno, "sigtimedwait() failed: %m");
 144                                 return;
 145                         }
 146
 147                         if (k >= 0)
 148                                 log_warning("sigtimedwait() returned unexpected signal.");
 149                 }
 150         }
 151 }
 152
 153 static int killall(int sig, Set *pids, bool send_sighup) {
 154         _cleanup_closedir_ DIR *dir = NULL;
 155         struct dirent *d;
 156
 157         dir = opendir("/proc");
 158         if (!dir)
 159                 return -errno;
 160
 161         FOREACH_DIRENT_ALL(d, dir, break) {
 162                 pid_t pid;
 163                 int r;
 164
 165                 if (!IN_SET(d->d_type, DT_DIR, DT_UNKNOWN))
 166                         continue;
 167
 168                 if (parse_pid(d->d_name, &pid) < 0)
 169                         continue;
 170
 171                 if (ignore_proc(pid, sig == SIGKILL && !in_initrd()))
 172                         continue;
 173
 174                 if (sig == SIGKILL) {
 175                         _cleanup_free_ char *s = NULL;
 176
 177                         get_process_comm(pid, &s);
 178                         log_notice("Sending SIGKILL to PID "PID_FMT" (%s).", pid, strna(s));
 179                 }
 180
 181                 if (kill(pid, sig) >= 0) {
 182                         if (pids) {
 183                                 r = set_put(pids, PID_TO_PTR(pid));
 184                                 if (r < 0)
 185                                         log_oom();
 186                         }
 187                 } else if (errno != ENOENT)
 188                         log_warning_errno(errno, "Could not kill %d: %m", pid);
 189
 190                 if (send_sighup) {
 191                         /* Optionally, also send a SIGHUP signal, but
 192                         only if the process has a controlling
 193                         tty. This is useful to allow handling of
 194                         shells which ignore SIGTERM but react to
 195                         SIGHUP. We do not send this to processes that
 196                         have no controlling TTY since we don't want to
 197                         trigger reloads of daemon processes. Also we
 198                         make sure to only send this after SIGTERM so
 199                         that SIGTERM is always first in the queue. */
 200
 201
 202                         if (get_ctty_devnr(pid, NULL) >= 0)
 203                                 /* it's OK if the process is gone, just ignore the result */
 204                                 (void) kill(pid, SIGHUP);
 205                 }
 206         }
 207
 208         return set_size(pids);
 209 }
 210
 211 void broadcast_signal(int sig, bool wait_for_exit, bool send_sighup, usec_t timeout) {
 212         sigset_t mask, oldmask;
 213         _cleanup_set_free_ Set *pids = NULL;
 214
 215         if (wait_for_exit)
 216                 pids = set_new(NULL);
 217
 218         assert_se(sigemptyset(&mask) == 0);
 219         assert_se(sigaddset(&mask, SIGCHLD) == 0);
 220         assert_se(sigprocmask(SIG_BLOCK, &mask, &oldmask) == 0);
 221
 222         if (kill(-1, SIGSTOP) < 0 && errno != ESRCH)
 223                 log_warning_errno(errno, "kill(-1, SIGSTOP) failed: %m");
 224
 225         killall(sig, pids, send_sighup);
 226
 227         if (kill(-1, SIGCONT) < 0 && errno != ESRCH)
 228                 log_warning_errno(errno, "kill(-1, SIGCONT) failed: %m");
 229
 230         if (wait_for_exit)
 231                 wait_for_children(pids, &mask, timeout);
 232
 233         assert_se(sigprocmask(SIG_SETMASK, &oldmask, NULL) == 0);
 234 }