Bug 1595470 - Prevent EnsureCorrectPermissions from making faulty assumptions about childBuffer r=rstrong

Differential Revision: https://phabricator.services.mozilla.com/D52604

--HG--
extra : moz-landing-system : lando

toolkit/mozapps/update/common/commonupdatedir.cpp

@@ -1510,12 +1510,6 @@ static HRESULT EnsureCorrectPermissions(SimpleAutoString& path,
     return returnValue;
   }
 
-  SimpleAutoString childBuffer;
-  if (!childBuffer.AllocEmpty(MAX_PATH)) {
-    // Fatal error. We need a buffer to put the path in.
-    return FAILED(returnValue) ? returnValue : E_OUTOFMEMORY;
-  }
-
   // Recurse into the directory.
   DIR directoryHandle(path.String());
   errno = 0;
@@ -1526,6 +1520,13 @@ static HRESULT EnsureCorrectPermissions(SimpleAutoString& path,
       continue;
     }
 
+    SimpleAutoString childBuffer;
+    if (!childBuffer.AllocEmpty(MAX_PATH)) {
+      // Just return on this failure rather than continuing. It is unlikely that
+      // this error will go away for the next path we try.
+      return FAILED(returnValue) ? returnValue : E_OUTOFMEMORY;
+    }
+
     childBuffer.AssignSprintf(MAX_PATH + 1, L"%s\\%s", path.String(),
                               entry->d_name);
     if (childBuffer.Length() == 0) {