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Create a new MOUNT_EXTERNAL_LEGACY storage mode.

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Apps that are already installed on the device before isolated_storage
feature is enabled will be granted MOUNT_EXTERNAL_LEGACY mode. In this
mode, /mnt/runtime/write will be mounted at /storage giving them same
level of access as in P.

A new mount directory /mnt/runtime/full is also created which will be
used for mounting at /storage for apps started with MOUNT_EXTERNAL_FULL
mode. This will allow apps with WRITE_MEDIA_STORAGE permission to
read/write anywhere on the secondary devices without needing to bypass
sdcardfs.

Bug: 121277410
Test: manual
Test: atest android.appsecurity.cts.ExternalStorageHostTest
Change-Id: Icc1ff9da35545692daedef7173d7c89290dd2766
This commit is contained in:
Sudheer Shanka 2019-01-09 12:15:15 -08:00
parent 811de623a0
commit 5504901bf0
4 changed files with 29 additions and 38 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

22
VolumeManager.cpp
View file

@ -425,8 +425,13 @@ int VolumeManager::mountPkgSpecificDirsForRunningProcs(
return -1;
}
struct stat fullWriteSb;
if (TEMP_FAILURE_RETRY(stat("/mnt/runtime/write", &fullWriteSb)) == -1) {
struct stat mntFullSb;
struct stat mntWriteSb;
if (TEMP_FAILURE_RETRY(stat("/mnt/runtime/full", &mntFullSb)) == -1) {
PLOG(ERROR) << "Failed to stat /mnt/runtime/full";
return -1;
}
if (TEMP_FAILURE_RETRY(stat("/mnt/runtime/write", &mntWriteSb)) == -1) {
PLOG(ERROR) << "Failed to stat /mnt/runtime/write";
return -1;
}
@ -505,7 +510,8 @@ int VolumeManager::mountPkgSpecificDirsForRunningProcs(
int mountMode;
if (remountMode == -1) {
mountMode = getMountModeForRunningProc(packagesForUid, userId, fullWriteSb);
mountMode =
getMountModeForRunningProc(packagesForUid, userId, mntWriteSb, mntFullSb);
if (mountMode == -1) {
_exit(1);
}
@ -525,6 +531,7 @@ int VolumeManager::mountPkgSpecificDirsForRunningProcs(
}
}
if (mountMode == VoldNativeService::REMOUNT_MODE_FULL ||
mountMode == VoldNativeService::REMOUNT_MODE_LEGACY ||
mountMode == VoldNativeService::REMOUNT_MODE_NONE) {
// These mount modes are not going to change dynamically, so don't bother
// unmounting/remounting dirs.
@ -578,7 +585,8 @@ int VolumeManager::mountPkgSpecificDirsForRunningProcs(
}
int VolumeManager::getMountModeForRunningProc(const std::vector<std::string>& packagesForUid,
userid_t userId, struct stat& mntWriteStat) {
userid_t userId, struct stat& mntWriteStat,
struct stat& mntFullStat) {
struct stat storageSb;
if (TEMP_FAILURE_RETRY(stat("/storage", &storageSb)) == -1) {
PLOG(ERROR) << "Failed to stat /storage";
@ -586,9 +594,11 @@ int VolumeManager::getMountModeForRunningProc(const std::vector<std::string>& pa
}
// Some packages have access to full external storage, identify processes belonging
// to those packages by comparing inode no.s of /mnt/runtime/write and /storage
if (storageSb.st_dev == mntWriteStat.st_dev && storageSb.st_ino == mntWriteStat.st_ino) {
// to those packages by comparing inode no.s of /mnt/runtime/full and /storage
if (storageSb.st_dev == mntFullStat.st_dev && storageSb.st_ino == mntFullStat.st_ino) {
return VoldNativeService::REMOUNT_MODE_FULL;
} else if (storageSb.st_dev == mntWriteStat.st_dev && storageSb.st_ino == mntWriteStat.st_ino) {
return VoldNativeService::REMOUNT_MODE_LEGACY;
}
std::string obbMountFile =

2
VolumeManager.h
View file

@ -174,7 +174,7 @@ class VolumeManager {
int destroySandboxForAppOnVol(const std::string& packageName, const std::string& sandboxId,
userid_t userId, const std::string& volLabel);
int getMountModeForRunningProc(const std::vector<std::string>& packagesForUid, userid_t userId,
struct stat& mntWriteStat);
struct stat& mntWriteStat, struct stat& mntFullStat);
void handleDiskAdded(const std::shared_ptr<android::vold::Disk>& disk);
void handleDiskChanged(dev_t device);

5
binder/android/os/IVold.aidl
View file

@ -151,8 +151,9 @@ interface IVold {
const int REMOUNT_MODE_DEFAULT = 1;
const int REMOUNT_MODE_READ = 2;
const int REMOUNT_MODE_WRITE = 3;
const int REMOUNT_MODE_INSTALLER = 4;
const int REMOUNT_MODE_FULL = 5;
const int REMOUNT_MODE_LEGACY = 4;
const int REMOUNT_MODE_INSTALLER = 5;
const int REMOUNT_MODE_FULL = 6;
const int VOLUME_STATE_UNMOUNTED = 0;
const int VOLUME_STATE_CHECKING = 1;

38
model/PublicVolume.cpp
View file

@ -185,36 +185,16 @@ status_t PublicVolume::doMount() {
PLOG(ERROR) << "Failed to exec";
}
} else {
// In Pre-Q, apps have full read access to secondary storage devices but only
// write access for their package specific directories. In Q, they only have access
// to their own sandboxes and they can write anywhere inside the sandbox. Instead of
// updating sdcardfs to allow packages writing into their own sandboxes, we could
// just allow them to write anywhere by passing "-w".
// clang-format off
if (GetBoolProperty(kIsolatedStorage, false)) {
if (execl(kFusePath, kFusePath,
"-u", "1023", // AID_MEDIA_RW
"-g", "1023", // AID_MEDIA_RW
"-U", std::to_string(getMountUserId()).c_str(),
"-w",
mRawPath.c_str(),
stableName.c_str(),
NULL)) {
// clang-format on
PLOG(ERROR) << "Failed to exec";
}
} else {
// clang-format off
if (execl(kFusePath, kFusePath,
"-u", "1023", // AID_MEDIA_RW
"-g", "1023", // AID_MEDIA_RW
"-U", std::to_string(getMountUserId()).c_str(),
mRawPath.c_str(),
stableName.c_str(),
NULL)) {
// clang-format on
PLOG(ERROR) << "Failed to exec";
}
if (execl(kFusePath, kFusePath,
"-u", "1023", // AID_MEDIA_RW
"-g", "1023", // AID_MEDIA_RW
"-U", std::to_string(getMountUserId()).c_str(),
mRawPath.c_str(),
stableName.c_str(),
NULL)) {
// clang-format on
PLOG(ERROR) << "Failed to exec";
}
}