[SampleProfile] Fix UB in Demangler invocation. #137659
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Currently the backing buffer of a std::vector<char> is passed[1] to Demangler.getFunctionBaseName. However, deeply inside the call stack OutputBuffer::grow will call[2] std::realloc if it needs to grow the buffer, leading to UB. The demangler APIs specify[3] that "Buf and N behave like the second and third parameters to __cxa_demangle" and the docs for the latter say[4] that the output buffer must be allocated with malloc (but can also be NULL and will then be realloced accordingly). [1]: https://github.com/llvm/llvm-project/blob/d7e631c7cd6d9c13b9519991ec6becf08bc6b8aa/llvm/lib/Transforms/IPO/SampleProfileMatcher.cpp#L744 [2]: https://github.com/llvm/llvm-project/blob/d7e631c7cd6d9c13b9519991ec6becf08bc6b8aa/llvm/include/llvm/Demangle/Utility.h#L50 [3]: https://github.com/llvm/llvm-project/blob/d7e631c7cd6d9c13b9519991ec6becf08bc6b8aa/llvm/include/llvm/Demangle/Demangle.h#L92-L93 [4]: https://gcc.gnu.org/onlinedocs/libstdc++/libstdc++-html-USERS-4.3/a01696.html
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@llvm/pr-subscribers-pgo @llvm/pr-subscribers-llvm-transforms Author: Krzysztof Pszeniczny (amharc) ChangesCurrently the backing buffer of a The demangler APIs specify3 that " Note: PR #135863 changed this from a stack array to a Full diff: https://github.com/llvm/llvm-project/pull/137659.diff 1 Files Affected:
diff --git a/llvm/lib/Transforms/IPO/SampleProfileMatcher.cpp b/llvm/lib/Transforms/IPO/SampleProfileMatcher.cpp
index 963c321772d6e..fdb5631f415a0 100644
--- a/llvm/lib/Transforms/IPO/SampleProfileMatcher.cpp
+++ b/llvm/lib/Transforms/IPO/SampleProfileMatcher.cpp
@@ -737,14 +737,13 @@ bool SampleProfileMatcher::functionMatchesProfileHelper(
auto FunctionName = FName.str();
if (Demangler.partialDemangle(FunctionName.c_str()))
return std::string();
- constexpr size_t MaxBaseNameSize = 65536;
- std::vector<char> BaseNameBuf(MaxBaseNameSize, 0);
- size_t BaseNameSize = MaxBaseNameSize;
- char *BaseNamePtr =
- Demangler.getFunctionBaseName(BaseNameBuf.data(), &BaseNameSize);
- return (BaseNamePtr && BaseNameSize)
- ? std::string(BaseNamePtr, BaseNameSize)
- : std::string();
+ size_t BaseNameSize = 0;
+ char *BaseNamePtr = Demangler.getFunctionBaseName(nullptr, &BaseNameSize);
+ std::string Result = (BaseNamePtr && BaseNameSize)
+ ? std::string(BaseNamePtr, BaseNameSize)
+ : std::string();
+ free(BaseNamePtr);
+ return Result;
};
auto IRBaseName = GetBaseName(IRFunc.getName());
auto ProfBaseName = GetBaseName(ProfFunc.stringRef());
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wlei-llvm
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Apr 28, 2025
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LGTM, thanks for the fix!
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/88/builds/11019 Here is the relevant piece of the build log for the reference |
IanWood1
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May 6, 2025
Currently the backing buffer of a `std::vector<char>` is passed[1] to `Demangler.getFunctionBaseName`. However, deeply inside the call stack `OutputBuffer::grow` will call[2] `std::realloc` if it needs to grow the buffer, leading to UB. The demangler APIs specify[3] that "`Buf` and `N` behave like the second and third parameters to `__cxa_demangle`" and the docs for the latter say[4] that the output buffer must be allocated with `malloc` (but can also be `NULL` and will then be realloced accordingly). Note: PR llvm#135863 changed this from a stack array to a `std::vector` and increased the size to 65K, but this can still lead to a crash if the demangled name is longer than that - yes, I'm surprised that a >65K-long function name happens in practice... [1]: https://github.com/llvm/llvm-project/blob/d7e631c7cd6d9c13b9519991ec6becf08bc6b8aa/llvm/lib/Transforms/IPO/SampleProfileMatcher.cpp#L744 [2]: https://github.com/llvm/llvm-project/blob/d7e631c7cd6d9c13b9519991ec6becf08bc6b8aa/llvm/include/llvm/Demangle/Utility.h#L50 [3]: https://github.com/llvm/llvm-project/blob/d7e631c7cd6d9c13b9519991ec6becf08bc6b8aa/llvm/include/llvm/Demangle/Demangle.h#L92-L93 [4]: https://gcc.gnu.org/onlinedocs/libstdc++/libstdc++-html-USERS-4.3/a01696.html
GeorgeARM
pushed a commit
to GeorgeARM/llvm-project
that referenced
this pull request
May 7, 2025
Currently the backing buffer of a `std::vector<char>` is passed[1] to `Demangler.getFunctionBaseName`. However, deeply inside the call stack `OutputBuffer::grow` will call[2] `std::realloc` if it needs to grow the buffer, leading to UB. The demangler APIs specify[3] that "`Buf` and `N` behave like the second and third parameters to `__cxa_demangle`" and the docs for the latter say[4] that the output buffer must be allocated with `malloc` (but can also be `NULL` and will then be realloced accordingly). Note: PR llvm#135863 changed this from a stack array to a `std::vector` and increased the size to 65K, but this can still lead to a crash if the demangled name is longer than that - yes, I'm surprised that a >65K-long function name happens in practice... [1]: https://github.com/llvm/llvm-project/blob/d7e631c7cd6d9c13b9519991ec6becf08bc6b8aa/llvm/lib/Transforms/IPO/SampleProfileMatcher.cpp#L744 [2]: https://github.com/llvm/llvm-project/blob/d7e631c7cd6d9c13b9519991ec6becf08bc6b8aa/llvm/include/llvm/Demangle/Utility.h#L50 [3]: https://github.com/llvm/llvm-project/blob/d7e631c7cd6d9c13b9519991ec6becf08bc6b8aa/llvm/include/llvm/Demangle/Demangle.h#L92-L93 [4]: https://gcc.gnu.org/onlinedocs/libstdc++/libstdc++-html-USERS-4.3/a01696.html
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Currently the backing buffer of a
std::vector<char>is passed1 toDemangler.getFunctionBaseName. However, deeply inside the call stackOutputBuffer::growwill call2std::reallocif it needs to grow the buffer, leading to UB.The demangler APIs specify3 that "
BufandNbehave like the second and third parameters to__cxa_demangle" and the docs for the latter say4 that the output buffer must be allocated withmalloc(but can also beNULLand will then be realloced accordingly).Note: PR #135863 changed this from a stack array to a
std::vectorand increased the size to 65K, but this can still lead to a crash if the demangled name is longer than that - yes, I'm surprised that a >65K-long function name happens in practice...