[Mlir-commits] [mlir] [mlir] Fix use-after-free bugs in {RankedTensorType|VectorType}::Builder (PR #68969)

[Benjamin Maxwell]

https://github.com/MacDue created https://github.com/llvm/llvm-project/pull/68969

Previously, these would set their ArrayRef members to reference their storage SmallVectors after a copy-on-write operation. This leads to a use-after-free if the builder is copied and the original destroyed (as the new builder would still reference the old SmallVector).

The VectorType::Builder also set the ArrayRef<bool> scalableDims member to a temporary SmallVector when the provided scalableDims are empty. This again lead to a use-after-free, and is unnecessary as VectorType::get already handles being passed an empty scalableDims array.

These bugs were in-part caught by UBSAN, see:
https://lab.llvm.org/buildbot/#/builders/5/builds/37355

>From 081be10b57e31a785b2b8db84cb3447eababf36d Mon Sep 17 00:00:00 2001
From: Benjamin Maxwell <benjamin.maxwell at arm.com>
Date: Fri, 13 Oct 2023 09:33:25 +0000
Subject: [PATCH] [mlir] Fix use-after-free bugs in
 {RankedTensorType|VectorType}::Builder

Previously, these would set their ArrayRef members to reference their
storage SmallVectors after a copy-on-write operation. This leads to a
use-after-free if the builder is copied and the original destroyed (as
the new builder would still reference the old SmallVector).

The VectorType::Builder also set the ArrayRef<bool> scalableDims member
to a temporary SmallVector when the provided scalableDims are empty.
This again lead to a use-after-free, and is unnecessary as
VectorType::get already handles being passed an empty scalableDims
array.

These bugs were in-part caught by UBSAN, see:
https://lab.llvm.org/buildbot/#/builders/5/builds/37355
---
 mlir/include/mlir/IR/BuiltinTypes.h | 43 ++++++++++++++++-------------
 1 file changed, 24 insertions(+), 19 deletions(-)

diff --git a/mlir/include/mlir/IR/BuiltinTypes.h b/mlir/include/mlir/IR/BuiltinTypes.h
index 9df5548cd5d939c..13fbae90b68c6cb 100644
--- a/mlir/include/mlir/IR/BuiltinTypes.h
+++ b/mlir/include/mlir/IR/BuiltinTypes.h
@@ -277,7 +277,7 @@ class RankedTensorType::Builder {
     if (storage.empty())
       storage.append(shape.begin(), shape.end());
     storage.erase(storage.begin() + pos);
-    shape = {storage.data(), storage.size()};
+    shape = {};
     return *this;
   }
 
@@ -287,12 +287,17 @@ class RankedTensorType::Builder {
     if (storage.empty())
       storage.append(shape.begin(), shape.end());
     storage.insert(storage.begin() + pos, val);
-    shape = {storage.data(), storage.size()};
+    shape = {};
     return *this;
   }
 
+  /// Returns the current shape.
+  ArrayRef<int64_t> getShape() {
+    return shape.empty() ? ArrayRef(storage) : shape;
+  }
+
   operator RankedTensorType() {
-    return RankedTensorType::get(shape, elementType, encoding);
+    return RankedTensorType::get(getShape(), elementType, encoding);
   }
 
 private:
@@ -319,20 +324,11 @@ class VectorType::Builder {
   /// Build from scratch.
   Builder(ArrayRef<int64_t> shape, Type elementType,
           unsigned numScalableDims = 0, ArrayRef<bool> scalableDims = {})
-      : shape(shape), elementType(elementType) {
-    if (scalableDims.empty())
-      scalableDims = SmallVector<bool>(shape.size(), false);
-    else
-      this->scalableDims = scalableDims;
-  }
+      : shape(shape), elementType(elementType), scalableDims(scalableDims) {}
 
   Builder &setShape(ArrayRef<int64_t> newShape,
                     ArrayRef<bool> newIsScalableDim = {}) {
-    if (newIsScalableDim.empty())
-      scalableDims = SmallVector<bool>(shape.size(), false);
-    else
-      scalableDims = newIsScalableDim;
-
+    scalableDims = newIsScalableDim;
     shape = newShape;
     return *this;
   }
@@ -351,9 +347,8 @@ class VectorType::Builder {
       storageScalableDims.append(scalableDims.begin(), scalableDims.end());
     storage.erase(storage.begin() + pos);
     storageScalableDims.erase(storageScalableDims.begin() + pos);
-    shape = {storage.data(), storage.size()};
-    scalableDims =
-        ArrayRef<bool>(storageScalableDims.data(), storageScalableDims.size());
+    shape = {};
+    scalableDims = {};
     return *this;
   }
 
@@ -363,12 +358,22 @@ class VectorType::Builder {
       storage.append(shape.begin(), shape.end());
     assert(pos < storage.size() && "overflow");
     storage[pos] = val;
-    shape = {storage.data(), storage.size()};
+    shape = {};
     return *this;
   }
 
+  /// Returns the current shape.
+  ArrayRef<int64_t> getShape() {
+    return shape.empty() ? ArrayRef(storage) : shape;
+  }
+
+  /// Returns the current scalable dims.
+  ArrayRef<bool> getScalableDims() {
+    return scalableDims.empty() ? ArrayRef(storageScalableDims) : scalableDims;
+  }
+
   operator VectorType() {
-    return VectorType::get(shape, elementType, scalableDims);
+    return VectorType::get(getShape(), elementType, getScalableDims());
   }
 
 private: