From 5a4bf02ff57e4dd3453f2b868c72fe45f60033a3 Mon Sep 17 00:00:00 2001

From: Harald Hoyer <harald@redhat.com>

Date: Thu, 21 Aug 2014 16:21:26 +0200

Subject: [PATCH] use the switch_root function in shutdown

removes code duplication

also move switch-root to shared

---

 Makefile.am                        |  4 +-

 src/core/main.c                    |  4 +-

 src/core/shutdown.c                | 90 +++++++-------------------------------

 src/{core => shared}/switch-root.c | 35 +++++++--------

 src/{core => shared}/switch-root.h |  2 +-

 5 files changed, 39 insertions(+), 96 deletions(-)

 rename src/{core => shared}/switch-root.c (81%)

 rename src/{core => shared}/switch-root.h (88%)

diff --git a/Makefile.am b/Makefile.am

index e091febc1f..1facb8da43 100644

--- a/Makefile.am

+++ b/Makefile.am

@@ -868,6 +868,8 @@ libsystemd_shared_la_SOURCES = \

 	src/shared/memfd.h \

 	src/shared/uid-range.c \

 	src/shared/uid-range.h \

+	src/shared/switch-root.h \

+	src/shared/switch-root.c \

 	src/shared/nss-util.h

 nodist_libsystemd_shared_la_SOURCES = \

@@ -1109,8 +1111,6 @@ libsystemd_core_la_SOURCES = \

 	src/core/namespace.h \

 	src/core/build.h \

 	src/core/sysfs-show.h \

-	src/core/switch-root.h \

-	src/core/switch-root.c \

 	src/core/killall.h \

 	src/core/killall.c \

 	src/core/audit-fd.c \

diff --git a/src/core/main.c b/src/core/main.c

index 95ab40fffc..64c2b3f3a1 100644

--- a/src/core/main.c

+++ b/src/core/main.c

@@ -1853,8 +1853,8 @@ finish:

                          * deserializing. */

                         broadcast_signal(SIGTERM, false, true);

-                        /* And switch root */

-                        r = switch_root(switch_root_dir);

+                        /* And switch root with MS_MOVE, because we remove the old directory afterwards and detach it. */

+                        r = switch_root(switch_root_dir, "/mnt", true, MS_MOVE);

                         if (r < 0)

                                 log_error("Failed to switch root, ignoring: %s", strerror(-r));

                 }

diff --git a/src/core/shutdown.c b/src/core/shutdown.c

index 0e2ea5754f..1e88b05790 100644

--- a/src/core/shutdown.c

+++ b/src/core/shutdown.c

@@ -48,6 +48,7 @@

 #include "killall.h"

 #include "cgroup-util.h"

 #include "def.h"

+#include "switch-root.h"

 #define FINALIZE_ATTEMPTS 50

@@ -131,16 +132,7 @@ static int parse_argv(int argc, char *argv[]) {

         return 0;

 }

-static int prepare_new_root(void) {

-        static const char dirs[] =

-                "/run/initramfs/oldroot\0"

-                "/run/initramfs/proc\0"

-                "/run/initramfs/sys\0"

-                "/run/initramfs/dev\0"

-                "/run/initramfs/run\0";

-

-        const char *dir;

-

+static int switch_root_initramfs(void) {

         if (mount("/run/initramfs", "/run/initramfs", NULL, MS_BIND, NULL) < 0) {

                 log_error("Failed to mount bind /run/initramfs on /run/initramfs: %m");

                 return -errno;

@@ -151,66 +143,13 @@ static int prepare_new_root(void) {

                 return -errno;

         }

-        NULSTR_FOREACH(dir, dirs)

-                if (mkdir_p_label(dir, 0755) < 0 && errno != EEXIST) {

-                        log_error("Failed to mkdir %s: %m", dir);

-                        return -errno;

-                }

-

-        if (mount("/sys", "/run/initramfs/sys", NULL, MS_BIND, NULL) < 0) {

-                log_error("Failed to mount bind /sys on /run/initramfs/sys: %m");

-                return -errno;

-        }

-

-        if (mount("/proc", "/run/initramfs/proc", NULL, MS_BIND, NULL) < 0) {

-                log_error("Failed to mount bind /proc on /run/initramfs/proc: %m");

-                return -errno;

-        }

-

-        if (mount("/dev", "/run/initramfs/dev", NULL, MS_BIND, NULL) < 0) {

-                log_error("Failed to mount bind /dev on /run/initramfs/dev: %m");

-                return -errno;

-        }

-

-        if (mount("/run", "/run/initramfs/run", NULL, MS_BIND, NULL) < 0) {

-                log_error("Failed to mount bind /run on /run/initramfs/run: %m");

-                return -errno;

-        }

-

-        return 0;

+        /* switch_root with MS_BIND, because there might still be processes lurking around, which have open file desriptors.

+         * /run/initramfs/shutdown will take care of these.

+         * Also do not detach the old root, because /run/initramfs/shutdown needs to access it.

+         */

+        return switch_root("/run/initramfs", "/oldroot", false, MS_BIND);

 }

-static int pivot_to_new_root(void) {

-

-        if (chdir("/run/initramfs") < 0) {

-                log_error("Failed to change directory to /run/initramfs: %m");

-                return -errno;

-        }

-

-        /* Work-around for a kernel bug: for some reason the kernel

-         * refuses switching root if any file systems are mounted

-         * MS_SHARED. Hence remount them MS_PRIVATE here as a

-         * work-around.

-         *

-         * https://bugzilla.redhat.com/show_bug.cgi?id=847418 */

-        if (mount(NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0)

-                log_warning("Failed to make \"/\" private mount: %m");

-

-        if (pivot_root(".", "oldroot") < 0) {

-                log_error("pivot failed: %m");

-                /* only chroot if pivot root succeeded */

-                return -errno;

-        }

-

-        chroot(".");

-

-        setsid();

-        make_console_stdio();

-

-        log_info("Successfully changed into root pivot.");

-

-        return 0;

-}

 int main(int argc, char *argv[]) {

         bool need_umount, need_swapoff, need_loop_detach, need_dm_detach;

@@ -372,16 +311,21 @@ int main(int argc, char *argv[]) {

         if (!in_container && !in_initrd() &&

             access("/run/initramfs/shutdown", X_OK) == 0) {

-

-                if (prepare_new_root() >= 0 &&

-                    pivot_to_new_root() >= 0) {

+                r = switch_root_initramfs();

+                if (r >= 0) {

                         arguments[0] = (char*) "/shutdown";

-                        log_info("Returning to initrd...");

+                        setsid();

+                        make_console_stdio();

+

+                        log_info("Successfully changed into root pivot.\n"

+                                 "Returning to initrd...");

                         execv("/shutdown", arguments);

                         log_error("Failed to execute shutdown binary: %m");

-                }

+                } else

+                        log_error("Failed to switch root to \"/run/initramfs\": %s", strerror(-r));

+

         }

         if (need_umount || need_swapoff || need_loop_detach || need_dm_detach)

diff --git a/src/core/switch-root.c b/src/shared/switch-root.c

similarity index 81%

rename from src/core/switch-root.c

rename to src/shared/switch-root.c

index 0ea61dbb29..5f075e6003 100644

--- a/src/core/switch-root.c

+++ b/src/shared/switch-root.c

@@ -34,7 +34,7 @@

 #include "base-filesystem.h"

 #include "missing.h"

-int switch_root(const char *new_root) {

+int switch_root(const char *new_root, const char *oldroot, bool detach_oldroot,  unsigned long mountflags) {

         /*  Don't try to unmount/move the old "/", there's no way to do it. */

         static const char move_mounts[] =

@@ -52,14 +52,8 @@ int switch_root(const char *new_root) {

         if (path_equal(new_root, "/"))

                 return 0;

-        /* When using pivot_root() we assume that /mnt exists as place

-         * we can temporarily move the old root to. As we immediately

-         * unmount it from there it doesn't matter much which

-         * directory we choose for this, but it should be more likely

-         * than not that /mnt exists and is suitable as mount point

-         * and is on the same fs as the old root dir */

-        temporary_old_root = strappenda(new_root, "/mnt");

-        mkdir_p(temporary_old_root, 0755);

+        temporary_old_root = strappenda(new_root, oldroot);

+        mkdir_p_label(temporary_old_root, 0755);

         old_root_remove = in_initrd();

@@ -84,7 +78,7 @@ int switch_root(const char *new_root) {

                 snprintf(new_mount, sizeof(new_mount), "%s%s", new_root, i);

                 char_array_0(new_mount);

-                mkdir_p(new_mount, 0755);

+                mkdir_p_label(new_mount, 0755);

                 if ((stat(new_mount, &sb) < 0) ||

                     sb.st_dev != new_root_stat.st_dev) {

@@ -97,11 +91,16 @@ int switch_root(const char *new_root) {

                         continue;

                 }

-                if (mount(i, new_mount, NULL, MS_MOVE, NULL) < 0) {

-                        log_error("Failed to move mount %s to %s, forcing unmount: %m", i, new_mount);

+                if (mount(i, new_mount, NULL, mountflags, NULL) < 0) {

+                        if (mountflags & MS_MOVE) {

+                                log_error("Failed to move mount %s to %s, forcing unmount: %m", i, new_mount);

+

+                                if (umount2(i, MNT_FORCE) < 0)

+                                        log_warning("Failed to unmount %s: %m", i);

+                        }

+                        if (mountflags & MS_BIND)

+                                log_error("Failed to bind mount %s to %s: %m", i, new_mount);

-                        if (umount2(i, MNT_FORCE) < 0)

-                                log_warning("Failed to unmount %s: %m", i);

                 }

         }

@@ -127,10 +126,10 @@ int switch_root(const char *new_root) {

          * not possible however, and hence we simply overmount root */

         if (pivot_root(new_root, temporary_old_root) >= 0) {

-                /* Immediately get rid of the old root. Since we are

-                 * running off it we need to do this lazily. */

-                if (umount2("/mnt", MNT_DETACH) < 0) {

-                        log_error("Failed to umount old root dir /mnt: %m");

+                /* Immediately get rid of the old root, if detach_oldroot is set.

+                 * Since we are running off it we need to do this lazily. */

+                if (detach_oldroot && umount2(oldroot, MNT_DETACH) < 0) {

+                        log_error("Failed to umount old root dir %s: %m", oldroot);

                         return -errno;

                 }

diff --git a/src/core/switch-root.h b/src/shared/switch-root.h

similarity index 88%

rename from src/core/switch-root.h

rename to src/shared/switch-root.h

index ab493b5fb1..adf893a922 100644

--- a/src/core/switch-root.h

+++ b/src/shared/switch-root.h

@@ -21,4 +21,4 @@

   along with systemd; If not, see <http://www.gnu.org/licenses/>.

 ***/

-int switch_root(const char *switch_root);

+int switch_root(const char *new_root, const char *oldroot, bool detach_oldroot, unsigned long mountflags);