core: go on a killing spree when transitioning from initrd to main system

1 files changed, 176 insertions, 0 deletions

diff --git a/src/core/killall.c b/src/core/killall.c
new file mode 100644
index 000000000..5f589eaf4
--- /dev/null
+++ b/src/core/killall.c
@@ -0,0 +1,176 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 ProFUSION embedded systems
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <sys/wait.h>
+#include <signal.h>
+#include <errno.h>
+
+#include "util.h"
+#include "def.h"
+#include "killall.h"
+
+#define TIMEOUT_USEC (5 * USEC_PER_SEC)
+
+static bool ignore_proc(pid_t pid) {
+        char buf[PATH_MAX];
+        FILE *f;
+        char c;
+        size_t count;
+        uid_t uid;
+        int r;
+
+        /* We are PID 1, let's not commit suicide */
+        if (pid == 1)
+                return true;
+
+        r = get_process_uid(pid, &uid);
+        if (r < 0)
+                return true; /* not really, but better safe than sorry */
+
+        /* Non-root processes otherwise are always subject to be killed */
+        if (uid != 0)
+                return false;
+
+        snprintf(buf, sizeof(buf), "/proc/%lu/cmdline", (unsigned long) pid);
+        char_array_0(buf);
+
+        f = fopen(buf, "re");
+        if (!f)
+                return true; /* not really, but has the desired effect */
+
+        count = fread(&c, 1, 1, f);
+        fclose(f);
+
+        /* Kernel threads have an empty cmdline */
+        if (count <= 0)
+                return true;
+
+        /* Processes with argv[0][0] = '@' we ignore from the killing
+         * spree.
+         *
+         * http://www.freedesktop.org/wiki/Software/systemd/RootStorageDaemons */
+        if (count == 1 && c == '@')
+                return true;
+
+        return false;
+}
+
+static void wait_for_children(int n_processes, sigset_t *mask) {
+        usec_t until;
+
+        assert(mask);
+
+        until = now(CLOCK_MONOTONIC) + TIMEOUT_USEC;
+        for (;;) {
+                struct timespec ts;
+                int k;
+                usec_t n;
+
+                for (;;) {
+                        pid_t pid = waitpid(-1, NULL, WNOHANG);
+
+                        if (pid == 0)
+                                break;
+
+                        if (pid < 0 && errno == ECHILD)
+                                return;
+
+                        if (n_processes > 0)
+                                if (--n_processes == 0)
+                                        return;
+                }
+
+                n = now(CLOCK_MONOTONIC);
+                if (n >= until)
+                        return;
+
+                timespec_store(&ts, until - n);
+
+                if ((k = sigtimedwait(mask, NULL, &ts)) != SIGCHLD) {
+
+                        if (k < 0 && errno != EAGAIN) {
+                                log_error("sigtimedwait() failed: %m");
+                                return;
+                        }
+
+                        if (k >= 0)
+                                log_warning("sigtimedwait() returned unexpected signal.");
+                }
+        }
+}
+
+static int killall(int sig) {
+        DIR *dir;
+        struct dirent *d;
+        unsigned int n_processes = 0;
+
+        dir = opendir("/proc");
+        if (!dir)
+                return -errno;
+
+        while ((d = readdir(dir))) {
+                pid_t pid;
+
+                if (d->d_type != DT_DIR &&
+                    d->d_type != DT_UNKNOWN)
+                        continue;
+
+                if (parse_pid(d->d_name, &pid) < 0)
+                        continue;
+
+                if (ignore_proc(pid))
+                        continue;
+
+                if (kill(pid, sig) >= 0)
+                        n_processes++;
+                else if (errno != ENOENT)
+                        log_warning("Could not kill %d: %m", pid);
+        }
+
+        closedir(dir);
+
+        return n_processes;
+}
+
+void broadcast_signal(int sig) {
+        sigset_t mask, oldmask;
+        int n_processes;
+
+        assert_se(sigemptyset(&mask) == 0);
+        assert_se(sigaddset(&mask, SIGCHLD) == 0);
+        assert_se(sigprocmask(SIG_BLOCK, &mask, &oldmask) == 0);
+
+        if (kill(-1, SIGSTOP) < 0 && errno != ESRCH)
+                log_warning("kill(-1, SIGSTOP) failed: %m");
+
+        n_processes = killall(sig);
+
+        if (kill(-1, SIGCONT) < 0 && errno != ESRCH)
+                log_warning("kill(-1, SIGCONT) failed: %m");
+
+        if (n_processes <= 0)
+                goto finish;
+
+        wait_for_children(n_processes, &mask);
+
+finish:
+        sigprocmask(SIG_SETMASK, &oldmask, NULL);
+}