Fix null pointer dereference in logging in mlir TransformOps

[apach301]

Hi,

I found with static analysis a possible null pointer overflow during error logging at mlir IR/TransformOps.cpp:

llvm-project/mlir/lib/Dialect/Transform/IR/TransformOps.cpp

Lines 653 to 657 in b2c5e9b

	if (!typeConverterOp) {
	InFlightDiagnostic diag = emitOpError()
	<< "expected default converter child op to "
	"implement TypeConverterBuilderOpInterface";
	diag.attachNote(typeConverterOp->getLoc()) << "op without interface";

A variable typeConverterOp may be nullptr after dynamic cast. There is a security guard for this, but during logging error message the variable getting dereferenced.

[github-actions]

Thank you for submitting a Pull Request (PR) to the LLVM Project!

This PR will be automatically labeled and the relevant teams will be
notified.

If you wish to, you can add reviewers by using the "Reviewers" section on this page.

If this is not working for you, it is probably because you do not have write
permissions for the repository. In which case you can instead tag reviewers by
name in a comment by using @ followed by their GitHub username.

If you have received no comments on your PR for a week, you can request a review
by "ping"ing the PR by adding a comment “Ping”. The common courtesy "ping" rate
is once a week. Please remember that you are asking for valuable time from other developers.

If you have further questions, they may be answered by the LLVM GitHub User Guide.

You can also ask questions in a comment on this PR, on the LLVM Discord or on the forums.

[llvmbot]

@llvm/pr-subscribers-mlir

Author: Daniel Kuts (apach301)

Changes

Hi,

I found with static analysis a possible null pointer overflow during error logging at mlir IR/TransformOps.cpp:

llvm-project/mlir/lib/Dialect/Transform/IR/TransformOps.cpp

Lines 653 to 657 in b2c5e9b

	if (!typeConverterOp) {
	InFlightDiagnostic diag = emitOpError()
	<< "expected default converter child op to "
	"implement TypeConverterBuilderOpInterface";
	diag.attachNote(typeConverterOp->getLoc()) << "op without interface";

A variable typeConverterOp may be nullptr after dynamic cast. There is a security guard for this, but during logging error message the variable getting dereferenced.

---

Full diff: https://github.com/llvm/llvm-project/pull/92237.diff

1 Files Affected:

• (modified) mlir/lib/Dialect/Transform/IR/TransformOps.cpp (+4-3)

diff --git a/mlir/lib/Dialect/Transform/IR/TransformOps.cpp b/mlir/lib/Dialect/Transform/IR/TransformOps.cpp
index eb09f007fbca8..5a9996dde48f7 100644
--- a/mlir/lib/Dialect/Transform/IR/TransformOps.cpp
+++ b/mlir/lib/Dialect/Transform/IR/TransformOps.cpp
@@ -648,13 +648,14 @@ LogicalResult transform::ApplyConversionPatternsOp::verify() {
     if (!llvm::hasSingleElement(typeConverterRegion.front()))
       return emitOpError()
              << "expected exactly one op in default type converter region";
-    auto typeConverterOp = dyn_cast<transform::TypeConverterBuilderOpInterface>(
-        &typeConverterRegion.front().front());
+
+    Operation *maybeTypeConverter = &typeConverterRegion.front().front();
+    auto typeConverterOp = dyn_cast<transform::TypeConverterBuilderOpInterface>(maybeTypeConverter);
     if (!typeConverterOp) {
       InFlightDiagnostic diag = emitOpError()
                                 << "expected default converter child op to "
                                    "implement TypeConverterBuilderOpInterface";
-      diag.attachNote(typeConverterOp->getLoc()) << "op without interface";
+      diag.attachNote(maybeTypeConverter->getLoc()) << "op without interface";
       return diag;
     }
     // Check default type converter type.

[ftynse]

Thanks!

[apach301]

Discussion on these changes: #92125

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff ca4a405232cf170f20a2f111bf72beab82095935 a06d869bdff05ade316e42b68983110ca6a93510 -- mlir/lib/Dialect/Transform/IR/TransformOps.cpp

View the diff from clang-format here.

diff --git a/mlir/lib/Dialect/Transform/IR/TransformOps.cpp b/mlir/lib/Dialect/Transform/IR/TransformOps.cpp
index 648fd33f8c..247759e21e 100644
--- a/mlir/lib/Dialect/Transform/IR/TransformOps.cpp
+++ b/mlir/lib/Dialect/Transform/IR/TransformOps.cpp
@@ -649,8 +649,8 @@ LogicalResult transform::ApplyConversionPatternsOp::verify() {
       return emitOpError()
              << "expected exactly one op in default type converter region";
     Operation *maybeTypeConverter = &typeConverterRegion.front().front();
-    auto typeConverterOp =
-        dyn_cast<transform::TypeConverterBuilderOpInterface>(maybeTypeConverter);
+    auto typeConverterOp = dyn_cast<transform::TypeConverterBuilderOpInterface>(
+        maybeTypeConverter);
     if (!typeConverterOp) {
       InFlightDiagnostic diag = emitOpError()
                                 << "expected default converter child op to "

[github-actions]

@apach301 Congratulations on having your first Pull Request (PR) merged into the LLVM Project!

Your changes will be combined with recent changes from other authors, then tested
by our build bots. If there is a problem with a build, you may receive a report in an email or a comment on this PR.

Please check whether problems have been caused by your change specifically, as
the builds can include changes from many authors. It is not uncommon for your
change to be included in a build that fails due to someone else's changes, or
infrastructure issues.

How to do this, and the rest of the post-merge process, is covered in detail here.

If your change does cause a problem, it may be reverted, or you can revert it yourself.
This is a normal part of LLVM development. You can fix your changes and open a new PR to merge them again.

If you don't get any reports, no action is required from you. Your changes are working as expected, well done!