[clang] Fix a use-after free in ASTContext::getSubstBuiltinTemplatePack #160970
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ASTContext::getSubstBuiltinTemplatePack finds InsertPos and then calls itself recursively, which may lead to rehashing and invalidation of all pointers to buckets. The function then proceeds with using the potentially invalid InsertPos, leading to use-after-free. I didn't manage to produce a reasonably-sized test case yet.
llvmbot
added
clang
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@llvm/pr-subscribers-clang Author: Alexander Kornienko (alexfh) ChangesASTContext::getSubstBuiltinTemplatePack finds InsertPos and then calls itself I didn't manage to produce a reasonably-sized test case yet. Full diff: https://github.com/llvm/llvm-project/pull/160970.diff 1 Files Affected:
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 07d42e7e2f3b3..e9d3e58f81cf2 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -5873,8 +5873,14 @@ ASTContext::getSubstBuiltinTemplatePack(const TemplateArgument &ArgPack) {
QualType Canon;
TemplateArgument CanonArgPack = getCanonicalTemplateArgument(ArgPack);
- if (!CanonArgPack.structurallyEquals(ArgPack))
+ if (!CanonArgPack.structurallyEquals(ArgPack)) {
Canon = getSubstBuiltinTemplatePack(CanonArgPack);
+ // Refresh InsertPos, in case the recursive call above caused rehashing,
+ // which would invalidate the bucket pointer.
+ if (auto *T =
+ SubstBuiltinTemplatePackTypes.FindNodeOrInsertPos(ID, InsertPos))
+ return QualType(T, 0);
+ }
auto *PackType = new (*this, alignof(SubstBuiltinTemplatePackType))
SubstBuiltinTemplatePackType(Canon, ArgPack);
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mizvekov
reviewed
Sep 27, 2025
Assert that a node is not found when refreshing InsertPos.
mizvekov
approved these changes
Sep 27, 2025
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/59/builds/24848 Here is the relevant piece of the build log for the reference |
mahesh-attarde
pushed a commit
to mahesh-attarde/llvm-project
that referenced
this pull request
Oct 3, 2025
…ck (llvm#160970) ASTContext::getSubstBuiltinTemplatePack finds InsertPos and then calls itself recursively, which may lead to rehashing and invalidation of all pointers to buckets. The function then proceeds with using the potentially invalid InsertPos, leading to use-after-free. The issue goes back to llvm#157662. I didn't manage to produce a reasonably-sized test case yet.
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ASTContext::getSubstBuiltinTemplatePack finds InsertPos and then calls itself
recursively, which may lead to rehashing and invalidation of all pointers to
buckets. The function then proceeds with using the potentially invalid
InsertPos, leading to use-after-free.
The issue goes back to #157662.
I didn't manage to produce a reasonably-sized test case yet.