src/core/killall.c

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