Fix invalid function pointer cast in cpuinfo.c #275
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While casting function pointers is allowed in C, the function must
ultimately be called through a pointer with the same type signature as
the function itself. Type signature mismatches, even decaying T* to
void* is undefined behavior.
UBSan flags this with -fsanitize=function. The easiest way I found to
repro this was:
CC=clang-18 CXX=clang++-18 \
CFLAGS="-fsanitize=function -fno-sanitize-recover=function" \
CXXFLAGS="-fsanitize=function -fno-sanitize-recover=function" \
cmake -GNinja -B build -DCPUINFO_BUILD_BENCHMARKS=OFF
ninja -C build
./build/cpu-info
That gives the following error:
[...]/src/linux/multiline.c:85:11: runtime error: call to function parse_line through pointer to incorrect function type 'bool (*)(const char *, const char *, void *, unsigned long)'
cpuinfo.c: note: parse_line defined here
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior [...]/src/linux/multiline.c:85:11
The fix is fairly straightforward: just keep the function at the type
signature the expected, and cast void* instead the function instead.
|
friendly ping |
digantdesai
approved these changes
Mar 21, 2025
|
This broke clang-format, @digantdesai why did you merge it before requesting fixes to the format? |
Merged
malfet
added a commit
that referenced
this pull request
May 22, 2025
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While casting function pointers is allowed in C, the function must ultimately be called through a pointer with the same type signature as the function itself. Type signature mismatches, even decaying T* to void* is undefined behavior.
UBSan flags this with -fsanitize=function. The easiest way I found to repro this was:
That gives the following error:
The fix is fairly straightforward: just keep the function at the type signature the expected, and cast void* instead the function instead.