【fuzz】heap-buffer-overflow

[qweryzh]

we fuzz-test about latest 3.6.4 libsass and find a heap-buffer-overflow bug to be fixed：
steps:
1、build
python3 infra/helper.py build_fuzzers --sanitizer address libsass
2、run
python3 infra/helper.py run_fuzzer libsass data_context_fuzzer -rss_limit_mb=0
error messages listed:
==13==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000003815 at pc 0x0000005a3a27 bp 0x7ffcbbed05d0 sp 0x7ffcbbed05c8
READ of size 1 at 0x602000003815 thread T0
SCARINESS: 12 (1-byte-read-heap-buffer-overflow)
#0 0x5a3a26 in Sass::handle_error(Sass_Context*) /src/libsass/src/sass_context.cpp:81:28
#1 0x59d780 in handle_errors /src/libsass/src/sass_context.cpp:207:18
#2 0x59d780 in sass_parse_block /src/libsass/src/sass_context.cpp:253:19
#3 0x59d780 in sass_compiler_parse /src/libsass/src/sass_context.cpp:483:22
#4 0x59c744 in sass_compile_context(Sass_Context*, Sass::Context*) /src/libsass/src/sass_context.cpp:371:7
#5 0x599f86 in LLVMFuzzerTestOneInput /src/data_context_fuzzer.cc:26:3
#6 0x4a21d1 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:556:15
#7 0x4a1915 in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool*) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:470:3
#8 0x4a39e7 in fuzzer::Fuzzer::MutateAndTestOne() /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:698:19
#9 0x4a4465 in fuzzer::Fuzzer::Loop(std::__Fuzzer::vector<fuzzer::SizedFile, fuzzer::fuzzer_allocatorfuzzer::SizedFile >&) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:832:5
#10 0x49343e in fuzzer::FuzzerDriver(int*, char***, int ()(unsigned char const, unsigned long)) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:826:6
#11 0x4bbc12 in main /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerMain.cpp:19:10
#12 0x7f390c9c482f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
#13 0x467b48 in _start (/out/data_context_fuzzer+0x467b48)

0x602000003815 is located 2 bytes to the right of 3-byte region [0x602000003810,0x602000003813)
allocated by thread T0 here:
#0 0x56788d in malloc /src/llvm-project/compiler-rt/lib/asan/asan_malloc_linux.cpp:145:3
#1 0x599f00 in LLVMFuzzerTestOneInput /src/data_context_fuzzer.cc:4:29
#2 0x4a21d1 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:556:15
#3 0x4a1915 in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool*) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:470:3
#4 0x4a39e7 in fuzzer::Fuzzer::MutateAndTestOne() /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:698:19
#5 0x4a4465 in fuzzer::Fuzzer::Loop(std::__Fuzzer::vector<fuzzer::SizedFile, fuzzer::fuzzer_allocatorfuzzer::SizedFile >&) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:832:5
#6 0x49343e in fuzzer::FuzzerDriver(int*, char***, int ()(unsigned char const, unsigned long)) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:826:6
#7 0x4bbc12 in main /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerMain.cpp:19:10
#8 0x7f390c9c482f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)

SUMMARY: AddressSanitizer: heap-buffer-overflow /src/libsass/src/sass_context.cpp:81:28 in Sass::handle_error(Sass_Context*)
Shadow bytes around the buggy address:
0x0c047fff86b0: fa fa fd fd fa fa fd fa fa fa fd fa fa fa fd fd
0x0c047fff86c0: fa fa fd fa fa fa fd fa fa fa fd fd fa fa fd fa
0x0c047fff86d0: fa fa fd fd fa fa fd fa fa fa fd fd fa fa fd fa
0x0c047fff86e0: fa fa fd fa fa fa fd fa fa fa fd fa fa fa fd fa
0x0c047fff86f0: fa fa fd fa fa fa fd fd fa fa fd fa fa fa 02 fa
=>0x0c047fff8700: fa fa[03]fa fa fa 00 03 fa fa fd fa fa fa 06 fa
0x0c047fff8710: fa fa 00 03 fa fa fd fa fa fa 00 fa fa fa 00 00
0x0c047fff8720: fa fa 06 fa fa fa 06 fa fa fa 00 00 fa fa 06 fa
0x0c047fff8730: fa fa 00 00 fa fa fd fa fa fa fd fd fa fa fa fa
0x0c047fff8740: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff8750: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
Shadow gap: cc
==13==ABORTING
MS: 3 CopyPart-ChangeByte-EraseBytes-; base unit: 4662e92f9aaa70ce2da332d3fc09c7d20a7f5388
0xa,0xf1,
\x0a\xf1
artifact_prefix='./'; Test unit written to ./crash-1715e03e9b724d06393bbbe585848f6ec76509fd
Base64: CvE=

hope reply it as soon as possible,thank you very much!