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Commit db620ef5 authored by Yi-Yo Chiang's avatar Yi-Yo Chiang
Browse files

fs_mgr_overlayfs: Fix "/" mount propagation type after remount 

If remounting "/system" caused "/" to be set to MS_PRIVATE, restore it
to MS_SHARED after remount.

Bug: 306124139
Test: adb-remount-test
Test: remount /system and verify /proc/self/mountinfo
Change-Id: I12bc2ccdaf7d2b2de330064b61a8533b96defe00
parent 686bff6e

fs_mgr/fs_mgr_overlayfs_mount.cpp

+15 −5
Original line number Diff line number Diff line
@@ -288,10 +288,6 @@ static bool fs_mgr_overlayfs_set_shared_mount(const std::string& mount_point, bo 
    if (ret) {

        PERROR << "__mount(target=" << mount_point

               << ",flag=" << (shared_flag ? "MS_SHARED" : "MS_PRIVATE") << ")=" << ret;

        // If "/system" doesn't look like a mountpoint, retry with "/".

        if (errno == EINVAL && mount_point == "/system") {

            return fs_mgr_overlayfs_set_shared_mount("/", shared_flag);

        }

        return false;

    }

    return true;
@@ -393,6 +389,8 @@ static bool fs_mgr_overlayfs_mount_one(const FstabEntry& fstab_entry) { 
    bool retval = true;

    bool move_dir_shared = true;

    bool parent_shared = true;

    bool root_shared = true;

    bool root_made_private = false;



    // There could be multiple mount entries with the same mountpoint.

    // Group these entries together with stable_sort, and keep only the last entry of a group.
@@ -419,6 +417,9 @@ static bool fs_mgr_overlayfs_mount_one(const FstabEntry& fstab_entry) { 
            (mount_point == "/system" && entry.mount_point == "/")) {

            parent_shared = entry.shared_flag;

        }

        if (entry.mount_point == "/") {

            root_shared = entry.shared_flag;

        }

    }



    // Precondition is that kMoveMountTempDir is MS_PRIVATE, otherwise don't try to move any
@@ -429,7 +430,13 @@ static bool fs_mgr_overlayfs_mount_one(const FstabEntry& fstab_entry) { 


    // Need to make the original mountpoint MS_PRIVATE, so that the overlayfs can be MS_MOVE.

    // This could happen if its parent mount is remounted later.

    fs_mgr_overlayfs_set_shared_mount(mount_point, false);

    if (!fs_mgr_overlayfs_set_shared_mount(mount_point, false)) {

        // If failed to set "/system" mount type, it might be due to "/system" not being a valid

        // mountpoint after switch root. Retry with "/" in this case.

        if (errno == EINVAL && mount_point == "/system") {

            root_made_private = fs_mgr_overlayfs_set_shared_mount("/", false);

        }

    }



    for (const auto& entry : mountinfo) {

        // Find all immediate submounts.
@@ -515,6 +522,9 @@ static bool fs_mgr_overlayfs_mount_one(const FstabEntry& fstab_entry) { 
    if (parent_shared) {

        fs_mgr_overlayfs_set_shared_mount(mount_point, true);

    }

    if (root_shared && root_made_private) {

        fs_mgr_overlayfs_set_shared_mount("/", true);

    }



    return retval;

}