diff --git a/cmds/installd/InstalldNativeService.cpp b/cmds/installd/InstalldNativeService.cpp
index c6132e8..b302f52 100644
--- a/cmds/installd/InstalldNativeService.cpp
+++ b/cmds/installd/InstalldNativeService.cpp
@@ -236,6 +236,16 @@
     }                                                       \
 }
 
+// we could have tighter checks, but this is only to avoid hard errors. Negative values are defined
+// in UserHandle.java and carry specific meanings that may not be handled by certain APIs here.
+#define ENFORCE_VALID_USER(userId)                                     \
+    {                                                                  \
+        if (static_cast<uid_t>(std::abs(userId)) >=                    \
+            std::numeric_limits<uid_t>::max() / AID_USER_OFFSET) {     \
+            return error("userId invalid: " + std::to_string(userId)); \
+        }                                                              \
+    }
+
 #define CHECK_ARGUMENT_UUID(uuid) {                         \
     binder::Status status = checkArgumentUuid((uuid));      \
     if (!status.isOk()) {                                   \
@@ -696,6 +706,7 @@
         int32_t flags, int32_t appId, int32_t previousAppId, const std::string& seInfo,
         int32_t targetSdkVersion, int64_t* _aidl_return) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     CHECK_ARGUMENT_PACKAGE_NAME(packageName);
 
@@ -790,6 +801,8 @@
 binder::Status InstalldNativeService::createSdkSandboxDataPackageDirectory(
         const std::optional<std::string>& uuid, const std::string& packageName, int32_t userId,
         int32_t appId, int32_t flags) {
+    ENFORCE_VALID_USER(userId);
+
     int32_t sdkSandboxUid = multiuser_get_sdk_sandbox_uid(userId, appId);
     if (sdkSandboxUid == -1) {
         // There no valid sdk sandbox process for this app. Skip creation of data directory
@@ -828,6 +841,7 @@
         int32_t flags, int32_t appId, int32_t previousAppId, const std::string& seInfo,
         int32_t targetSdkVersion, int64_t* _aidl_return) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     CHECK_ARGUMENT_PACKAGE_NAME(packageName);
     LOCK_PACKAGE_USER();
@@ -839,6 +853,7 @@
         const android::os::CreateAppDataArgs& args,
         android::os::CreateAppDataResult* _aidl_return) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(args.userId);
     // Locking is performed depeer in the callstack.
 
     int64_t ceDataInode = -1;
@@ -854,6 +869,10 @@
         const std::vector<android::os::CreateAppDataArgs>& args,
         std::vector<android::os::CreateAppDataResult>* _aidl_return) {
     ENFORCE_UID(AID_SYSTEM);
+    for (const auto& arg : args) {
+        ENFORCE_VALID_USER(arg.userId);
+    }
+
     // Locking is performed depeer in the callstack.
 
     std::vector<android::os::CreateAppDataResult> results;
@@ -868,6 +887,7 @@
 
 binder::Status InstalldNativeService::reconcileSdkData(
         const android::os::ReconcileSdkDataArgs& args) {
+    ENFORCE_VALID_USER(args.userId);
     // Locking is performed depeer in the callstack.
 
     return reconcileSdkData(args.uuid, args.packageName, args.subDirNames, args.userId, args.appId,
@@ -891,6 +911,7 @@
                                                        int userId, int appId, int previousAppId,
                                                        const std::string& seInfo, int flags) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     CHECK_ARGUMENT_PACKAGE_NAME(packageName);
     LOCK_PACKAGE_USER();
@@ -974,6 +995,7 @@
 binder::Status InstalldNativeService::migrateAppData(const std::optional<std::string>& uuid,
         const std::string& packageName, int32_t userId, int32_t flags) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     CHECK_ARGUMENT_PACKAGE_NAME(packageName);
     LOCK_PACKAGE_USER();
@@ -1041,6 +1063,7 @@
 binder::Status InstalldNativeService::clearAppData(const std::optional<std::string>& uuid,
         const std::string& packageName, int32_t userId, int32_t flags, int64_t ceDataInode) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     CHECK_ARGUMENT_PACKAGE_NAME(packageName);
     LOCK_PACKAGE_USER();
@@ -1132,6 +1155,7 @@
 binder::Status InstalldNativeService::clearSdkSandboxDataPackageDirectory(
         const std::optional<std::string>& uuid, const std::string& packageName, int32_t userId,
         int32_t flags) {
+    ENFORCE_VALID_USER(userId);
     const char* uuid_ = uuid ? uuid->c_str() : nullptr;
     const char* pkgname = packageName.c_str();
 
@@ -1218,6 +1242,7 @@
 binder::Status InstalldNativeService::destroyAppData(const std::optional<std::string>& uuid,
         const std::string& packageName, int32_t userId, int32_t flags, int64_t ceDataInode) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     CHECK_ARGUMENT_PACKAGE_NAME(packageName);
     LOCK_PACKAGE_USER();
@@ -1288,6 +1313,8 @@
 binder::Status InstalldNativeService::destroySdkSandboxDataPackageDirectory(
         const std::optional<std::string>& uuid, const std::string& packageName, int32_t userId,
         int32_t flags) {
+    ENFORCE_VALID_USER(userId);
+
     const char* uuid_ = uuid ? uuid->c_str() : nullptr;
     const char* pkgname = packageName.c_str();
 
@@ -1435,6 +1462,7 @@
                                                       int32_t userId, int32_t snapshotId,
                                                       int32_t storageFlags, int64_t* _aidl_return) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID_IS_TEST_OR_NULL(volumeUuid);
     CHECK_ARGUMENT_PACKAGE_NAME(packageName);
     LOCK_PACKAGE_USER();
@@ -1569,6 +1597,7 @@
         const int32_t appId, const std::string& seInfo, const int32_t userId,
         const int32_t snapshotId, int32_t storageFlags) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID_IS_TEST_OR_NULL(volumeUuid);
     CHECK_ARGUMENT_PACKAGE_NAME(packageName);
     LOCK_PACKAGE_USER();
@@ -1641,6 +1670,7 @@
         const int32_t userId, const int64_t ceSnapshotInode, const int32_t snapshotId,
         int32_t storageFlags) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID_IS_TEST_OR_NULL(volumeUuid);
     CHECK_ARGUMENT_PACKAGE_NAME(packageName);
     LOCK_PACKAGE_USER();
@@ -1674,6 +1704,7 @@
         const std::optional<std::string>& volumeUuid, const int32_t userId,
         const std::vector<int32_t>& retainSnapshotIds) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID_IS_TEST_OR_NULL(volumeUuid);
     LOCK_USER();
 
@@ -1864,6 +1895,7 @@
 binder::Status InstalldNativeService::createUserData(const std::optional<std::string>& uuid,
         int32_t userId, int32_t userSerial ATTRIBUTE_UNUSED, int32_t flags) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     LOCK_USER();
 
@@ -1884,6 +1916,7 @@
 binder::Status InstalldNativeService::destroyUserData(const std::optional<std::string>& uuid,
         int32_t userId, int32_t flags) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     LOCK_USER();
 
@@ -2671,6 +2704,7 @@
         int32_t userId, int32_t flags, const std::vector<int32_t>& appIds,
         std::vector<int64_t>* _aidl_return) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     // NOTE: Locking is relaxed on this method, since it's limited to
     // read-only measurements without mutation.
@@ -2806,6 +2840,7 @@
         int32_t userId, int32_t flags, const std::vector<int32_t>& appIds,
         std::vector<int64_t>* _aidl_return) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     // NOTE: Locking is relaxed on this method, since it's limited to
     // read-only measurements without mutation.
@@ -2926,6 +2961,7 @@
         const std::vector<std::string>& packageNames, int32_t userId,
         std::optional<std::vector<std::optional<CrateMetadata>>>* _aidl_return) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     for (const auto& packageName : packageNames) {
         CHECK_ARGUMENT_PACKAGE_NAME(packageName);
@@ -2975,6 +3011,7 @@
         const std::optional<std::string>& uuid, int32_t userId,
         std::optional<std::vector<std::optional<CrateMetadata>>>* _aidl_return) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
 #ifdef ENABLE_STORAGE_CRATES
     LOCK_USER();
@@ -3018,6 +3055,7 @@
 binder::Status InstalldNativeService::setAppQuota(const std::optional<std::string>& uuid,
         int32_t userId, int32_t appId, int64_t cacheQuota) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     std::lock_guard<std::recursive_mutex> lock(mQuotasLock);
 
@@ -3261,6 +3299,7 @@
         const std::string& packageName, int32_t userId, int32_t flags, int32_t appId,
         const std::string& seInfo) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     CHECK_ARGUMENT_PACKAGE_NAME(packageName);
     LOCK_PACKAGE_USER();
@@ -3271,6 +3310,7 @@
         const std::optional<std::string>& uuid, const std::string& packageName, int32_t userId,
         int32_t flags, int32_t appId, const std::string& seInfo) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     CHECK_ARGUMENT_PACKAGE_NAME(packageName);
 
@@ -3302,6 +3342,7 @@
         const std::optional<std::string>& uuid, const std::string& packageName, int32_t userId,
         int32_t flags, int32_t appId, const std::string& seInfo) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_UUID(uuid);
     CHECK_ARGUMENT_PACKAGE_NAME(packageName);
 
@@ -3753,6 +3794,7 @@
         int32_t userId, int32_t appId, const std::string& profileName, const std::string& codePath,
         const std::optional<std::string>& dexMetadata, bool* _aidl_return) {
     ENFORCE_UID(AID_SYSTEM);
+    ENFORCE_VALID_USER(userId);
     CHECK_ARGUMENT_PACKAGE_NAME(packageName);
     CHECK_ARGUMENT_PATH(codePath);
     LOCK_PACKAGE_USER();
@@ -3775,6 +3817,7 @@
 
 binder::Status InstalldNativeService::cleanupInvalidPackageDirs(
         const std::optional<std::string>& uuid, int32_t userId, int32_t flags) {
+    ENFORCE_VALID_USER(userId);
     const char* uuid_cstr = uuid ? uuid->c_str() : nullptr;
 
     if (flags & FLAG_STORAGE_CE) {