[flang-commits] [flang] cf63261 - [flang] Don't crash attempting to fold absurdly large TRANSFER()

[Peter Klausler via flang-commits]

Author: Peter Klausler
Date: 2022-12-16T11:43:14-08:00
New Revision: cf63261b7789ba42ca6db04cfec54a8524d7487b

URL: https://github.com/llvm/llvm-project/commit/cf63261b7789ba42ca6db04cfec54a8524d7487b
DIFF: https://github.com/llvm/llvm-project/commit/cf63261b7789ba42ca6db04cfec54a8524d7487b.diff

LOG: [flang] Don't crash attempting to fold absurdly large TRANSFER()

Apply some sanity checking to the type size and SIZE= values and
avoid crashing on stress tests that attempt to create excessively
large results.

Differential Revision: https://reviews.llvm.org/D140138

Added: 
    

Modified: 
    flang/lib/Evaluate/fold.cpp

Removed: 
    


################################################################################
diff  --git a/flang/lib/Evaluate/fold.cpp b/flang/lib/Evaluate/fold.cpp
index c78a0aa4c9ad..6f61a6829484 100644
--- a/flang/lib/Evaluate/fold.cpp
+++ b/flang/lib/Evaluate/fold.cpp
@@ -261,14 +261,21 @@ std::optional<Expr<SomeType>> FoldTransfer(
     }
   }
   if (sourceBytes && IsActuallyConstant(*source) && moldType && extents) {
-    InitialImage image{*sourceBytes};
-    InitialImage::Result imageResult{
-        image.Add(0, *sourceBytes, *source, context)};
-    CHECK(imageResult == InitialImage::Ok);
-    return image.AsConstant(context, *moldType, *extents, true /*pad with 0*/);
-  } else {
-    return std::nullopt;
+    std::size_t elements{
+        extents->empty() ? 1 : static_cast<std::size_t>((*extents)[0])};
+    std::size_t totalBytes{*sourceBytes * elements};
+    // Don't fold intentional overflow cases from sneaky tests
+    if (totalBytes < std::size_t{1000000} &&
+        (elements == 0 || totalBytes / elements == *sourceBytes)) {
+      InitialImage image{*sourceBytes};
+      InitialImage::Result imageResult{
+          image.Add(0, *sourceBytes, *source, context)};
+      CHECK(imageResult == InitialImage::Ok);
+      return image.AsConstant(
+          context, *moldType, *extents, true /*pad with 0*/);
+    }
   }
+  return std::nullopt;
 }
 
 template class ExpressionBase<SomeDerived>;