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shutdown: pivot_root to a tmpfs directory to properly umount root

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check for /run/initramfs/shutdown
mount bind all needed dirs to /run/initramfs
pivot_root to /run/initramfs
execute /run/initramfs/shutdown
This commit is contained in:
Harald Hoyer 2011-05-05 12:29:44 +02:00
parent 31657718f5
commit 7cb1094ace
2 changed files with 106 additions and 0 deletions
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4
src/missing.h
View File

@ -172,4 +172,8 @@ struct btrfs_ioctl_vol_args {
#define MS_MOVE 8192
#endif
#ifndef MS_PRIVATE
#define MS_PRIVATE (1 << 18)
#endif
#endif

102
src/shutdown.c
View File

@ -24,6 +24,11 @@
#include <sys/reboot.h>
#include <linux/reboot.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mount.h>
#include <sys/syscall.h>
#include <fcntl.h>
#include <dirent.h>
#include <errno.h>
#include <unistd.h>
@ -32,12 +37,14 @@
#include <stdlib.h>
#include <string.h>
#include "missing.h"
#include "log.h"
#include "umount.h"
#include "util.h"
#define TIMEOUT_USEC (5 * USEC_PER_SEC)
#define FINALIZE_ATTEMPTS 50
#define pivot_root(new_root,put_old) syscall(SYS_pivot_root,new_root,put_old)
static bool ignore_proc(pid_t pid) {
if (pid == 1)
@ -192,6 +199,90 @@ finish:
sigprocmask(SIG_SETMASK, &oldmask, NULL);
}
static bool prepare_new_root(void) {
int r = false;
const char *dirs[] = { "/run/initramfs/oldroot",
"/run/initramfs/proc",
"/run/initramfs/sys",
"/run/initramfs/dev",
"/run/initramfs/run",
NULL };
const char **dir;
const char *msg;
msg = "Failed to mount bind /run/initramfs on /run/initramfs";
if (mount("/run/initramfs", "/run/initramfs", NULL, MS_BIND, NULL) != 0)
goto out;
msg="Failed to make /run/initramfs private mount %m:";
if (mount(NULL, "/run/initramfs", NULL, MS_PRIVATE, NULL) != 0)
goto out;
for (dir = &dirs[0]; *dir != NULL; dir++) {
asprintf((char **) &msg, "mkdir %s: %%m", *dir);
if (mkdir(*dir, 0755) != 0) {
if (errno != EEXIST)
goto out;
}
free((char *) msg);
}
msg = "Failed to mount bind /sys on /run/initramfs/sys";
if (mount("/sys", "/run/initramfs/sys", NULL, MS_BIND, NULL) != 0)
goto out;
msg = "Failed to mount bind /proc on /run/initramfs/proc";
if (mount("/proc", "/run/initramfs/proc", NULL, MS_BIND, NULL) != 0)
goto out;
msg = "Failed to mount bind /dev on /run/initramfs/dev";
if (mount("/dev", "/run/initramfs/dev", NULL, MS_BIND, NULL) != 0)
goto out;
msg = "Failed to mount bind /run on /run/initramfs/run";
if (mount("/run", "/run/initramfs/run", NULL, MS_BIND, NULL) != 0)
goto out;
r = true;
out:
if (!r)
log_error("%s: %m", msg);
return r;
}
static bool pivot_to_new_root(void) {
int fd;
int r = 0;
chdir("/run/initramfs");
/*
In case some evil process made "/" MS_SHARED
It works for pivot_root, but the ref count for the root device
is not decreasing :-/
*/
if (mount(NULL, "/", NULL, MS_PRIVATE, NULL) != 0) {
log_error("Failed to make \"/\" private mount %m: ");
return false;
}
r = pivot_root(".", "oldroot");
if (r!=0) {
log_error("pivot failed: %m");
/* only chroot, if pivot root succeded */
return false;
}
chroot(".");
log_info("pivot rooted");
fd = open("dev/console", O_RDONLY);
dup2(fd, STDIN_FILENO);
close_nointr_nofail(fd);
fd = open("dev/console", O_WRONLY);
dup2(fd, STDOUT_FILENO);
close_nointr_nofail(fd);
fd = open("dev/console", O_WRONLY);
dup2(fd, STDERR_FILENO);
close_nointr_nofail(fd);
return true;
}
int main(int argc, char *argv[]) {
int cmd, r;
unsigned retries;
@ -330,6 +421,17 @@ int main(int argc, char *argv[]) {
sync();
if (access("/run/initramfs/shutdown", X_OK) == 0) {
char *new_argv[3];
new_argv[0] = strdup(argv[0]);
new_argv[1] = strdup(argv[1]);
new_argv[2] = NULL;
if (prepare_new_root() && pivot_to_new_root()) {
execv("/shutdown", new_argv);
log_error("Failed to execute shutdown binary: %m");
}
}
if (cmd == LINUX_REBOOT_CMD_KEXEC) {
/* We cheat and exec kexec to avoid doing all its work */
pid_t pid = fork();