[scudo] Avoid accessing inaccessible pages in unmap() in secondary (l…

…lvm#102367)

compiler-rt/lib/scudo/standalone/secondary.h

@@ -823,7 +823,11 @@ void MapAllocator<Config>::deallocate(const Options &Options, void *Ptr)
  Cache.store(Options, H->CommitBase, H->CommitSize,
  reinterpret_cast<uptr>(H + 1), H->MemMap);
  } else {
- unmap(H->MemMap);
+ // Note that the `H->MemMap` is stored on the pages managed by itself. Take
+ // over the ownership before unmap() so that any operation along with
+ // unmap() won't touch inaccessible pages.
+ MemMapT MemMap = H->MemMap;
+ unmap(MemMap);
  }
 }