diff --git a/src/com/android/providers/telephony/MmsProvider.java b/src/com/android/providers/telephony/MmsProvider.java
index a311788..da8f193 100644
--- a/src/com/android/providers/telephony/MmsProvider.java
+++ b/src/com/android/providers/telephony/MmsProvider.java
@@ -16,6 +16,7 @@
 
 package com.android.providers.telephony;
 
+import android.annotation.NonNull;
 import android.app.AppOpsManager;
 import android.content.ContentProvider;
 import android.content.ContentValues;
@@ -278,6 +279,11 @@
     @Override
     public Uri insert(Uri uri, ContentValues values) {
         // Don't let anyone insert anything with the _data column
+        // The _data column is filled internally in MmsProvider, so this check is just to avoid
+        // it from being inadvertently set. This is not supposed to be a protection against
+        // malicious attack, since sql injection could still be attempted to bypass the check. On
+        // the other hand, the MmsProvider does verify that the _data column has an allowed value
+        // before opening any uri/files.
         if (values != null && values.containsKey(Part._DATA)) {
             return null;
         }
@@ -702,9 +708,12 @@
     }
 
     @Override
-    public int update(Uri uri, ContentValues values,
-            String selection, String[] selectionArgs) {
-        // Don't let anyone update the _data column
+    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
+        // The _data column is filled internally in MmsProvider, so this check is just to avoid
+        // it from being inadvertently set. This is not supposed to be a protection against
+        // malicious attack, since sql injection could still be attempted to bypass the check. On
+        // the other hand, the MmsProvider does verify that the _data column has an allowed value
+        // before opening any uri/files.
         if (values != null && values.containsKey(Part._DATA)) {
             return 0;
         }
@@ -811,6 +820,12 @@
         }
 
         // Verify that the _data path points to mms data
+        return safeOpenFileHelper(uri, mode);
+    }
+
+    @NonNull
+    private ParcelFileDescriptor safeOpenFileHelper(
+           @NonNull Uri uri, @NonNull String mode) throws FileNotFoundException {
         Cursor c = query(uri, new String[]{"_data"}, null, null, null);
         int count = (c != null) ? c.getCount() : 0;
         if (count != 1) {
@@ -831,10 +846,15 @@
         c.close();
 
         if (path == null) {
-            return null;
+            throw new FileNotFoundException("Column _data not found.");
         }
+        File filePath = new File(path);
         try {
-            File filePath = new File(path);
+                // The MmsProvider shouldn't open a file that isn't MMS data, so we verify that the
+                // _data path actually points to MMS data. That safeguards ourselves from callers who
+                // inserted or updated a URI (more specifically the _data column) with disallowed paths.
+                // TODO(afurtado): provide a more robust mechanism to avoid disallowed _data paths to
+                // be inserted/updated in the first place, including via SQL injection.
             if (!filePath.getCanonicalPath()
                     .startsWith(getContext().getDir(PARTS_DIR_NAME, 0).getPath())) {
                 Log.e(TAG, "openFile: path "
@@ -842,7 +862,6 @@
                         + " does not start with "
                         + getContext().getDir(PARTS_DIR_NAME, 0).getPath());
                 // Don't care return value
-                filePath.delete();
                 return null;
             }
         } catch (IOException e) {
@@ -850,7 +869,8 @@
             return null;
         }
 
-        return openFileHelper(uri, mode);
+        int modeBits = ParcelFileDescriptor.parseMode(mode);
+        return ParcelFileDescriptor.open(filePath, modeBits);
     }
 
     private void filterUnsupportedKeys(ContentValues values) {