Do not allow a script to attach a prim if its being sat upon.

This prevents a stack overflow where a get position on the avatar will refer to the attachment which will in turn refer back to the avatar.
This required recording of all sitting avatars on a prim which is done separately from recording the sit target avatar.
Recording HashSet is null if there are no sitting avatars in order to save memory.

2 files changed, 40 insertions, 1 deletions

diff --git a/OpenSim/Region/CoreModules/Avatar/Attachments/AttachmentsModule.cs b/OpenSim/Region/CoreModules/Avatar/Attachments/AttachmentsModule.cs
index 9eb0e38..eccf7a6 100644
--- a/OpenSim/Region/CoreModules/Avatar/Attachments/AttachmentsModule.cs
+++ b/OpenSim/Region/CoreModules/Avatar/Attachments/AttachmentsModule.cs
@@ -251,6 +251,15 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
 //                m_log.DebugFormat(
 //                    "[ATTACHMENTS MODULE]: Attaching object {0} {1} to {2} point {3} from ground (silent = {4})",
 //                    group.Name, group.LocalId, sp.Name, attachmentPt, silent);
+
+                if (group.GetSittingAvatarsCount() != 0)
+                {
+//                    m_log.WarnFormat(
+//                        "[ATTACHMENTS MODULE]: Ignoring request to attach {0} {1} to {2} on {3} since {4} avatars are still sitting on it",
+//                        group.Name, group.LocalId, sp.Name, attachmentPt, group.GetSittingAvatarsCount());
+    
+                    return false;
+                }
     
                 if (sp.GetAttachments(attachmentPt).Contains(group))
                 {
diff --git a/OpenSim/Region/CoreModules/Avatar/Attachments/Tests/AttachmentsModuleTests.cs b/OpenSim/Region/CoreModules/Avatar/Attachments/Tests/AttachmentsModuleTests.cs
index 5dcbd28..3e06900 100644
--- a/OpenSim/Region/CoreModules/Avatar/Attachments/Tests/AttachmentsModuleTests.cs
+++ b/OpenSim/Region/CoreModules/Avatar/Attachments/Tests/AttachmentsModuleTests.cs
@@ -118,7 +118,7 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments.Tests
 
             Scene scene = CreateDefaultTestScene();
             UserAccount ua1 = UserAccountHelpers.CreateUserWithInventory(scene, 0x1);
-            ScenePresence sp = SceneHelpers.AddScenePresence(scene, ua1.PrincipalID);
+            ScenePresence sp = SceneHelpers.AddScenePresence(scene, ua1);
 
             string attName = "att";
 
@@ -154,6 +154,36 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments.Tests
 //            TestHelpers.DisableLogging();
         }
 
+        /// <summary>
+        /// Test that we do not attempt to attach an in-world object that someone else is sitting on.
+        /// </summary>
+        [Test]
+        public void TestAddSatOnAttachmentFromGround()
+        {
+            TestHelpers.InMethod();
+//            TestHelpers.EnableLogging();
+
+            Scene scene = CreateDefaultTestScene();
+            UserAccount ua1 = UserAccountHelpers.CreateUserWithInventory(scene, 0x1);
+            ScenePresence sp = SceneHelpers.AddScenePresence(scene, ua1);
+
+            string attName = "att";
+
+            SceneObjectGroup so = SceneHelpers.AddSceneObject(scene, attName, sp.UUID);
+
+            UserAccount ua2 = UserAccountHelpers.CreateUserWithInventory(scene, 0x2);
+            ScenePresence sp2 = SceneHelpers.AddScenePresence(scene, ua2);
+
+            // Put avatar within 10m of the prim so that sit doesn't fail.
+            sp2.AbsolutePosition = new Vector3(0, 0, 0);
+            sp2.HandleAgentRequestSit(sp2.ControllingClient, sp2.UUID, so.UUID, Vector3.Zero);
+
+            scene.AttachmentsModule.AttachObject(sp, so, (uint)AttachmentPoint.Chest, false);
+
+            Assert.That(sp.HasAttachments(), Is.False);
+            Assert.That(scene.GetSceneObjectGroups().Count, Is.EqualTo(1));
+        }
+
         [Test]
         public void TestAddAttachmentFromInventory()
         {