Adding public volume mounts for clone user.

Public SdCard Volumes are mounted only for user 0
(foreground user). This gives ENONT if the cloned
user tries to access the files in SdCard with
paths like "/storage/AB02-G212/DCIM/"

This change adds SdCard Volume mnt under
/mnt/usr/<cloned-user>/ which allows cloned apps
access to SdCard via direct file paths.

Bug: 203395175
Test: Manual by building and flashing device.
Change-Id: I091c40d3cb19915145cd5af40d1e79d5a9ecfa02

VolumeManager.cpp

@@ -68,6 +68,7 @@
 #include "model/EmulatedVolume.h"
 #include "model/ObbVolume.h"
 #include "model/PrivateVolume.h"
+#include "model/PublicVolume.h"
 #include "model/StubVolume.h"
 
 using android::OK;
@@ -88,6 +89,7 @@ using android::vold::IsVirtioBlkDevice;
 using android::vold::PrepareAndroidDirs;
 using android::vold::PrepareAppDirFromRoot;
 using android::vold::PrivateVolume;
+using android::vold::PublicVolume;
 using android::vold::Symlink;
 using android::vold::Unlink;
 using android::vold::UnmountTree;
@@ -457,6 +459,31 @@ int VolumeManager::onUserStarted(userid_t userId) {
 
     if (mStartedUsers.find(userId) == mStartedUsers.end()) {
         createEmulatedVolumesForUser(userId);
+        std::list<std::string> public_vols;
+        listVolumes(VolumeBase::Type::kPublic, public_vols);
+        for (const std::string& id : public_vols) {
+            PublicVolume* pvol = static_cast<PublicVolume*>(findVolume(id).get());
+            if (pvol->getState() != VolumeBase::State::kMounted) {
+                continue;
+            }
+            if (pvol->isVisible() == 0) {
+                continue;
+            }
+            userid_t mountUserId = pvol->getMountUserId();
+            if (userId == mountUserId) {
+                // No need to bind mount for the user that owns the mount
+                continue;
+            }
+            if (mountUserId != VolumeManager::Instance()->getSharedStorageUser(userId)) {
+                // No need to bind if the user does not share storage with the mount owner
+                continue;
+            }
+            auto bindMountStatus = pvol->bindMountForUser(userId);
+            if (bindMountStatus != OK) {
+                LOG(ERROR) << "Bind Mounting Public Volume: " << pvol << " for user: " << userId
+                           << "Failed. Error: " << bindMountStatus;
+            }
+        }
     }
 
     mStartedUsers.insert(userId);

model/PublicVolume.cpp

@@ -257,9 +257,45 @@ status_t PublicVolume::doMount() {
     // See comment in model/EmulatedVolume.cpp
     ConfigureMaxDirtyRatioForFuse(GetFuseMountPathForUser(user_id, stableName), 40u);
 
+    auto vol_manager = VolumeManager::Instance();
+    // Create bind mounts for all running users
+    for (userid_t started_user : vol_manager->getStartedUsers()) {
+        userid_t mountUserId = getMountUserId();
+        if (started_user == mountUserId) {
+            // No need to bind mount for the user that owns the mount
+            continue;
+        }
+        if (mountUserId != VolumeManager::Instance()->getSharedStorageUser(started_user)) {
+            // No need to bind if the user does not share storage with the mount owner
+            continue;
+        }
+        auto bindMountStatus = bindMountForUser(started_user);
+        if (bindMountStatus != OK) {
+            LOG(ERROR) << "Bind Mounting Public Volume: " << stableName
+                       << " for user: " << started_user << "Failed. Error: " << bindMountStatus;
+        }
+    }
     return OK;
 }
 
+status_t PublicVolume::bindMountForUser(userid_t user_id) {
+    userid_t mountUserId = getMountUserId();
+    std::string stableName = getId();
+    if (!mFsUuid.empty()) {
+        stableName = mFsUuid;
+    }
+
+    LOG(INFO) << "Bind Mounting Public Volume for user: " << user_id
+              << ".Mount owner: " << mountUserId;
+    auto sourcePath = GetFuseMountPathForUser(mountUserId, stableName);
+    auto destPath = GetFuseMountPathForUser(user_id, stableName);
+    PrepareDir(destPath, 0770, AID_ROOT, AID_MEDIA_RW);
+    auto mountRes = BindMount(sourcePath, destPath);
+    LOG(INFO) << "Mount status: " << mountRes;
+
+    return mountRes;
+}
+
 status_t PublicVolume::doUnmount() {
     // Unmount the storage before we kill the FUSE process. If we kill
     // the FUSE process first, most file system operations will return
@@ -274,6 +310,20 @@ status_t PublicVolume::doUnmount() {
             stableName = mFsUuid;
         }
 
+        // Unmount bind mounts for running users
+        auto vol_manager = VolumeManager::Instance();
+        int user_id = getMountUserId();
+        for (int started_user : vol_manager->getStartedUsers()) {
+            if (started_user == user_id) {
+                // No need to remove bind mount for the user that owns the mount
+                continue;
+            }
+            LOG(INFO) << "Removing Public Volume Bind Mount for: " << started_user;
+            auto mountPath = GetFuseMountPathForUser(started_user, stableName);
+            ForceUnmount(mountPath);
+            rmdir(mountPath.c_str());
+        }
+
         if (UnmountUserFuse(getMountUserId(), getInternalPath(), stableName) != OK) {
             PLOG(INFO) << "UnmountUserFuse failed on public fuse volume";
             return -errno;

model/PublicVolume.h

@@ -42,6 +42,8 @@ class PublicVolume : public VolumeBase {
     explicit PublicVolume(dev_t device);
     virtual ~PublicVolume();
 
+    status_t bindMountForUser(userid_t user_id);
+
   protected:
     status_t doCreate() override;
     status_t doDestroy() override;