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ASan now detects dereferences of zero-sized allocations (llvm#155943). This appears to have detected a bug in CrossOverTest.cpp, which this patch fixes. Buildbot: https://lab.llvm.org/buildbot/#/builders/4/builds/8732 7: ==949882==ERROR: AddressSanitizer: heap-buffer-overflow on address 0xf169cfbe0010 at pc 0xb5f45efc6d1c bp 0xffffd933e460 sp 0xffffd933e458 check:20'0 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8: READ of size 1 at 0xf169cfbe0010 thread T0 check:20'0 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9: #0 0xb5f45efc6d18 in LLVMFuzzerTestOneInput /home/tcwg-buildbot/worker/clang-aarch64-sve-vls-2stage/llvm/compiler-rt/test/fuzzer/CrossOverTest.cpp:48:7 check:20'0 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ check:20'1 ? possible intended match 10: #1 0xb5f45eec7288 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /home/tcwg-buildbot/worker/clang-aarch64-sve-vls-2stage/llvm/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:619:13 check:20'0 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 11: llvm#2 0xb5f45eec85d4 in fuzzer::Fuzzer::ReadAndExecuteSeedCorpora(std::vector<fuzzer::SizedFile, std::allocator<fuzzer::SizedFile>>&) /home/tcwg-buildbot/worker/clang-aarch64-sve-vls-2stage/llvm/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:812:3 check:20'0 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 12: llvm#3 0xb5f45eec8c60 in fuzzer::Fuzzer::Loop(std::vector<fuzzer::SizedFile, std::allocator<fuzzer::SizedFile>>&) /home/tcwg-buildbot/worker/clang-aarch64-sve-vls-2stage/llvm/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:872:3 check:20'0 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 13: llvm#4 0xb5f45eeb5c64 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /home/tcwg-buildbot/worker/clang-aarch64-sve-vls-2stage/llvm/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:923:6 check:20'0 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 14: llvm#5 0xb5f45eee09d0 in main /home/tcwg-buildbot/worker/clang-aarch64-sve-vls-2stage/llvm/compiler-rt/lib/fuzzer/FuzzerMain.cpp:20:10 check:20'0 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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@llvm/pr-subscribers-compiler-rt-sanitizer Author: Thurston Dang (thurstond) ChangesASan now detects dereferences of zero-sized allocations (#155943; the corresponding MSan change is #155944). This appears to have detected a bug in CrossOverTest.cpp, causing a buildbot breakage. This patch fixes the test. Buildbot report: https://lab.llvm.org/buildbot/#/builders/4/builds/8732 Full diff: https://github.com/llvm/llvm-project/pull/156103.diff 1 Files Affected:
diff --git a/compiler-rt/test/fuzzer/CrossOverTest.cpp b/compiler-rt/test/fuzzer/CrossOverTest.cpp
index b4506f665dc76..6d764d0b6a6bd 100644
--- a/compiler-rt/test/fuzzer/CrossOverTest.cpp
+++ b/compiler-rt/test/fuzzer/CrossOverTest.cpp
@@ -45,6 +45,9 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
// fprintf(stderr, "ExpectedHash: %x\n", ExpectedHash);
if (Size == 10 && ExpectedHash == simple_hash(Data, Size))
*NullPtr = 0;
+ // It's UB to read *Data when Size == 0
+ if (Size == 0)
+ return;
if (*Data == 'A')
Sink++;
if (*Data == 'Z')
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vitalybuka
approved these changes
Aug 29, 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/51/builds/22569 Here is the relevant piece of the build log for the reference |
thurstond
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Aug 29, 2025
#156103 was missing the return value
llvm-sync bot
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llvm/llvm-project#156103 was missing the return value
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/66/builds/18616 Here is the relevant piece of the build log for the reference |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/52/builds/10780 Here is the relevant piece of the build log for the reference |
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ASan now detects dereferences of zero-sized allocations (#155943; the corresponding MSan change is #155944). This appears to have detected a bug in CrossOverTest.cpp, causing a buildbot breakage. This patch fixes the test.
Buildbot report: https://lab.llvm.org/buildbot/#/builders/4/builds/8732
For context, FuzzerLoop.cpp:812 tries empty input: