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c/r: use /proc/self/tid/children instead of pidfile

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All we really needed a unique temp file for was passing the pid. Since CRIU
opened this with O_EXCL | O_CREAT, this was "safe" (users could still
overwrite it afterwards, but the monitor would immediately die since the
only valid number in there was the init process).

In any case, we can just read /proc/self/tid/children, which lists the
child process.

Closes #1150

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
This commit is contained in:
Tycho Andersen 2016-08-26 16:07:19 +00:00
parent e854c5e315
commit 75d219f0cc
1 changed files with 15 additions and 25 deletions
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40
src/lxc/criu.c
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@ -69,7 +69,6 @@ struct criu_opts {
char tty_id[32]; /* the criu tty id for /dev/console, i.e. "tty[${rdev}:${dev}]" */
/* restore: the file to write the init process' pid into */
char *pidfile;
const char *cgroup_path;
int console_fd;
/* The path that is bind mounted from /dev/console, if any. We don't
@ -176,10 +175,10 @@ static void exec_criu(struct criu_opts *opts)
static_args += 2;
} else if (strcmp(opts->action, "restore") == 0) {
/* --root $(lxc_mount_point) --restore-detached
* --restore-sibling --pidfile $foo --cgroup-root $foo
* --restore-sibling --cgroup-root $foo
* --lsm-profile apparmor:whatever
*/
static_args += 10;
static_args += 8;
tty_info[0] = 0;
if (load_tty_major_minor(opts->user->directory, tty_info, sizeof(tty_info)))
@ -330,8 +329,6 @@ static void exec_criu(struct criu_opts *opts)
DECLARE_ARG(opts->c->lxc_conf->rootfs.mount);
DECLARE_ARG("--restore-detached");
DECLARE_ARG("--restore-sibling");
DECLARE_ARG("--pidfile");
DECLARE_ARG(opts->pidfile);
DECLARE_ARG("--cgroup-root");
DECLARE_ARG(opts->cgroup_path);
@ -604,13 +601,8 @@ static void do_restore(struct lxc_container *c, int status_pipe, struct migrate_
{
pid_t pid;
struct lxc_handler *handler;
int fd, status;
int status;
int pipes[2] = {-1, -1};
char pidfile[] = "criu_restore_XXXXXX";
fd = mkstemp(pidfile);
if (fd < 0)
goto out;
handler = lxc_init(c->name, c->lxc_conf, c->config_path);
if (!handler)
@ -690,7 +682,6 @@ static void do_restore(struct lxc_container *c, int status_pipe, struct migrate_
os.action = "restore";
os.user = opts;
os.c = c;
os.pidfile = pidfile;
os.cgroup_path = cgroup_canonical_path(handler);
os.console_fd = c->lxc_conf->console.slave;
os.criu_version = criu_version;
@ -742,8 +733,9 @@ static void do_restore(struct lxc_container *c, int status_pipe, struct migrate_
}
if (WIFEXITED(status)) {
if (WEXITSTATUS(status)) {
char buf[4096];
if (WEXITSTATUS(status)) {
int n;
n = read(pipes[0], buf, sizeof(buf));
@ -758,18 +750,21 @@ static void do_restore(struct lxc_container *c, int status_pipe, struct migrate_
goto out_fini_handler;
} else {
int ret;
FILE *f = fdopen(fd, "r");
if (!f) {
SYSERROR("couldn't read restore's init pidfile %s\n", pidfile);
ret = snprintf(buf, sizeof(buf), "/proc/self/task/%" PRId64 "/children", syscall(__NR_gettid));
if (ret < 0 || ret >= sizeof(buf)) {
ERROR("snprintf'd too many characters: %d", ret);
goto out_fini_handler;
}
FILE *f = fopen(buf, "r");
if (!f) {
SYSERROR("couldn't read restore's children file %s\n", buf);
goto out_fini_handler;
}
fd = -1;
ret = fscanf(f, "%d", (int*) &handler->pid);
fclose(f);
if (unlink(pidfile) < 0 && errno != ENOENT)
SYSERROR("unlinking pidfile failed");
if (ret != 1) {
ERROR("reading restore pid failed");
goto out_fini_handler;
@ -809,8 +804,6 @@ out_fini_handler:
close(pipes[1]);
lxc_fini(c->name, handler);
if (unlink(pidfile) < 0 && errno != ENOENT)
SYSERROR("unlinking pidfile failed");
out:
if (status_pipe >= 0) {
@ -821,9 +814,6 @@ out:
close(status_pipe);
}
if (fd > 0)
close(fd);
exit(1);
}