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fs_mgr: overlay drop redundant check

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fs_mgr_update_verity_state() provides the needed result, we do not
need to check verity state manually.

Caveat:

The open-coded verity check is not 100% redundant, as it ensures
that if /vendor is not mounted, where the device mount table resides
to aid in a correct enumeration of all verity-enabled mount points,
that /system is not accidentally overlay mounted on a verity checked
volume.  This is a unlikely corner condition.  A fix for this
condition in the future is to instead migrate this redundant
checking into fs_mgr_update_verity_state() since system is
considered ever present and can be blindly performed without the
required /system or / mount point entries in fstab.  Note that
the overlay logic is #ifdef'd out on user builds, so it is not
really a security or reliability issue on a release build.

Test: manual
Bug: 109821005
Change-Id: Ib4a7f9438b2a3cb008e263605a7a7647737c40f2
This commit is contained in:
Mark Salyzyn 2018-08-29 10:44:33 -07:00
parent 4c67290da6
commit 21afa1693f
1 changed files with 5 additions and 11 deletions
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16
fs_mgr/fs_mgr_overlayfs.cpp
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@ -556,17 +556,11 @@ std::vector<std::string> fs_mgr_candidate_list(const fstab* fstab,
return mounts;
}
// Manually check dm state because stunted fstab (w/o system as root) borken
auto& dm = DeviceMapper::Instance();
auto found = false;
for (auto& system : {"system", "vroot"}) {
if (dm.GetState(system) == DmDeviceState::INVALID) continue;
std::vector<DeviceMapper::TargetInfo> table;
found = !dm.GetTableStatus(system, &table) || table.empty() || table[0].data.empty() ||
(table[0].data[0] == 'C') || (table[0].data[0] == 'V');
if (found) break;
}
if (!found) mounts.emplace_back("/system");
// 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;
}