Unmount in-place instead of using MS_MOVE.

To support multi-user emulated storage, we mount rootfs as MS_SHARED,
which means we can't MS_MOVE existing mount points rooted in the
shared subtree.  Initial staging is still able to MS_MOVE, since it's
rooted in a MS_PRIVATE tmpfs rooted at /mnt/secure.

This change fixes unmounting by operating in-place instead of trying
(and failing) to MS_MOVE back to staging.

Bug: 7127564
Change-Id: I4783db4319b61c0915da39361cbc7e8f4943d094

1 files changed, 10 insertions, 22 deletions

diff --git a/Volume.cpp b/Volume.cpp
index a71000e..0be2e81 100644
--- a/Volume.cpp
+++ b/Volume.cpp
@@ -608,41 +608,29 @@ int Volume::unmountVol(bool force, bool revert) {
     usleep(1000 * 1000); // Give the framework some time to react
 
     /*
-     * First move the mountpoint back to our internal staging point
-     * so nobody else can muck with it while we work.
+     * Remove the bindmount we were using to keep a reference to
+     * the previously obscured directory.
      */
-    if (doMoveMount(getMountpoint(), SEC_STGDIR, force)) {
-        SLOGE("Failed to move mount %s => %s (%s)", getMountpoint(), SEC_STGDIR, strerror(errno));
-        setState(Volume::State_Mounted);
-        return -1;
+    if (doUnmount(Volume::SEC_ASECDIR_EXT, force)) {
+        SLOGE("Failed to remove bindmount on %s (%s)", SEC_ASECDIR_EXT, strerror(errno));
+        goto fail_remount_tmpfs;
     }
 
-    protectFromAutorunStupidity();
-
     /*
      * Unmount the tmpfs which was obscuring the asec image directory
      * from non root users
      */
-
-    if (doUnmount(Volume::SEC_STG_SECIMGDIR, force)) {
-        SLOGE("Failed to unmount tmpfs on %s (%s)", SEC_STG_SECIMGDIR, strerror(errno));
+    char secure_dir[PATH_MAX];
+    snprintf(secure_dir, PATH_MAX, "%s/.android_secure", getMountpoint());
+    if (doUnmount(secure_dir, force)) {
+        SLOGE("Failed to unmount tmpfs on %s (%s)", secure_dir, strerror(errno));
         goto fail_republish;
     }
 
     /*
-     * Remove the bindmount we were using to keep a reference to
-     * the previously obscured directory.
-     */
-
-    if (doUnmount(Volume::SEC_ASECDIR_EXT, force)) {
-        SLOGE("Failed to remove bindmount on %s (%s)", SEC_ASECDIR_EXT, strerror(errno));
-        goto fail_remount_tmpfs;
-    }
-
-    /*
      * Finally, unmount the actual block device from the staging dir
      */
-    if (doUnmount(Volume::SEC_STGDIR, force)) {
+    if (doUnmount(getMountpoint(), force)) {
         SLOGE("Failed to unmount %s (%s)", SEC_STGDIR, strerror(errno));
         goto fail_recreate_bindmount;
     }