Reproduction steps

1. Build the tv-casting-app with AddressSanitizer (ASAN) enabled.

2. Open Terminal 1 and start the tv-casting-app:

   $ ./tv-casting-app

3. Open Terminal 2 and start the tv-app:

   $ ./tv-app

4. In the tv-casting-app shell, send a cast request:

   tv-casting-app > cast request 0

5. In the tv-app shell, respond with:

   tv-app > controller ux ok

6. In the tv-casting-app, print the list of fabrics and delete a specific fabric:

   tv-casting-app > cast print-fabrics
   tv-casting-app > cast delete-fabric <fabricId>

7. Observe the ASAN output in tv-casting-app indicating a heap-use-after-free issue.
   tv-casting-app UAF.txt

Summary

A heap-use-after-free (UAF) issue occurs in the tv-casting-app when the delete-fabric command is executed. After removing a fabric, the system attempts to access a freed ReadClient object.

Analysis and Description

The issue arises from a lifecycle mismatch between fabric cleanup and the ReadClient object references. The sequence of events leading to the issue is as follows:

1. Fabric Removal (FabricTable.cpp):

   • The Delete() method of FabricTable is called, which iterates through its delegates and invokes OnFabricRemoved():

     CHIP_ERROR FabricTable::Delete(FabricIndex fabricIndex)
     {
         if (mDelegateListRoot != nullptr)
         {
             FabricTable::Delegate * delegate = mDelegateListRoot;
             while (delegate)
             {
                 FabricTable::Delegate * nextDelegate = delegate->next;
                 delegate->OnFabricRemoved(*this, fabricIndex);
                 delegate = nextDelegate;
             }
         }
     }
     

2. ReadClient Cleanup (InteractionModelEngine.cpp):

   • The OnFabricRemoved() method loops through active ReadClient objects and calls Close():

     void InteractionModelEngine::OnFabricRemoved(const FabricTable & fabricTable, FabricIndex fabricIndex)
     {
         for (auto * readClient = mpActiveReadClientList; readClient != nullptr; readClient = readClient->GetNextClient())
         {
             if (readClient->GetFabricIndex() == fabricIndex)
             {
                 readClient->Close(CHIP_ERROR_IM_FABRIC_DELETED, false);
             }
         }
     }
     

3. ReadClient Deallocation (ReadClient.cpp):

   • The Close() method triggers the callback mpCallback.OnDone(this), marking the ReadClient for destruction:

     void ReadClient::Close(CHIP_ERROR aError, bool allowResubscription)
     {
         ...
         mpCallback.OnDone(this);
     }
     

4. Use of Freed Memory:

   • Despite being destroyed, the ReadClient remains in the mpActiveReadClientList. Subsequent iterations in OnFabricRemoved() access the dangling pointer. Specifically, the readClient->GetNextClient() call accesses the mpNext pointer of the destroyed ReadClient object, leading to a UAF:

     ReadClient * GetNextClient() { return mpNext; }

   • This happens because GetNextClient() does not verify the validity of the mpNext pointer, which now points to a deallocated memory region.

Bug prevalence

always

GitHub hash of the SDK that was being used

04e6a68

Platform

core

Platform Version(s)

all versions

Anything else?

No response