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Commit 6576e139 authored by Tom Cherry's avatar Tom Cherry
Browse files

Remove logic to fake /system in overlayfs 

It is better to guarantee that a /system or / entry will be present in
first stage mount than it is to maintain the code to fake an entry if
its not present in the input fstab.

Test: adb-remount-test.sh on blueline
Change-Id: I8aa3e704903b8abf06b1c63be071913a9de58eb3
parent 2210f80e

fs_mgr/fs_mgr_overlayfs.cpp

+0 −20
Original line number Diff line number Diff line
@@ -565,26 +565,6 @@ std::vector<std::string> fs_mgr_candidate_list(Fstab* fstab, const char* mount_p 
        if (!duplicate_or_more_specific) mounts.emplace_back(new_mount_point);

    }



    // if not itemized /system or /, system as root, fake one up?



    // do we want or need to?

    if (mount_point && ("/system"s != mount_point)) return mounts;

    if (std::find(mounts.begin(), mounts.end(), "/system") != mounts.end()) return mounts;



    // fs_mgr_overlayfs_verity_enabled_list says not to?

    if (std::find(verity.begin(), verity.end(), "system") != verity.end()) return mounts;



    // confirm that fstab is missing system

    if (GetEntryForMountPoint(fstab, "/") != nullptr ||

        GetEntryForMountPoint(fstab, "/system") != nullptr) {

        return mounts;

    }



    // We have a stunted fstab (w/o system or / ) passed in by the caller,

    // verity claims are assumed accurate because they are collected internally

    // from fs_mgr_fstab_default() from within fs_mgr_update_verity_state(),

    // Can (re)evaluate /system with impunity since we know it is ever-present.

    mounts.emplace_back("/system");

    return mounts;

}

init/first_stage_mount.cpp

+47 −1
Original line number Diff line number Diff line
@@ -157,6 +157,37 @@ static Fstab ReadFirstStageFstab() { 
    return fstab;

}



static bool GetRootEntry(FstabEntry* root_entry) {

    Fstab proc_mounts;

    if (!ReadFstabFromFile("/proc/mounts", &proc_mounts)) {

        LOG(ERROR) << "Could not read /proc/mounts and /system not in fstab, /system will not be "

                      "available for overlayfs";

        return false;

    }



    auto entry = std::find_if(proc_mounts.begin(), proc_mounts.end(), [](const auto& entry) {

        return entry.mount_point == "/" && entry.fs_type != "rootfs";

    });



    if (entry == proc_mounts.end()) {

        LOG(ERROR) << "Could not get mount point for '/' in /proc/mounts, /system will not be "

                      "available for overlayfs";

        return false;

    }



    *root_entry = std::move(*entry);



    // We don't know if we're avb or not, so we query device mapper as if we are avb.  If we get a

    // success, then mark as avb, otherwise default to verify.

    auto& dm = android::dm::DeviceMapper::Instance();

    if (dm.GetState("vroot") != android::dm::DmDeviceState::INVALID) {

        root_entry->fs_mgr_flags.avb = true;

    } else {

        root_entry->fs_mgr_flags.verify = true;

    }

    return true;

}



// Class Definitions

// -----------------

FirstStageMount::FirstStageMount(Fstab fstab)
@@ -443,7 +474,7 @@ bool FirstStageMount::TrySwitchSystemAsRoot() { 


    if (system_partition == fstab_.end()) return true;



    if (MountPartition(system_partition, true /* erase_used_fstab_entry */)) {

    if (MountPartition(system_partition, false)) {

        SwitchRoot("/system");

    } else {

        PLOG(ERROR) << "Failed to mount /system";
@@ -487,6 +518,12 @@ bool FirstStageMount::MountPartitions() { 
    if (!TrySkipMountingPartitions()) return false;



    for (auto current = fstab_.begin(); current != fstab_.end();) {

        // We've already mounted /system above.

        if (current->mount_point == "/system") {

            ++current;

            continue;

        }



        Fstab::iterator end;

        if (!MountPartition(current, false, &end)) {

            if (current->fs_mgr_flags.no_fail) {
@@ -503,6 +540,15 @@ bool FirstStageMount::MountPartitions() { 
        current = end;

    }



    // If we don't see /system or / in the fstab, then we need to create an root entry for

    // overlayfs.

    if (!GetEntryForMountPoint(&fstab_, "/system") && !GetEntryForMountPoint(&fstab_, "/")) {

        FstabEntry root_entry;

        if (GetRootEntry(&root_entry)) {

            fstab_.emplace_back(std::move(root_entry));

        }

    }



    // heads up for instantiating required device(s) for overlayfs logic

    const auto devices = fs_mgr_overlayfs_required_devices(&fstab_);

    for (auto const& device : devices) {