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authorLibravatar Andrzej Hunt <ajrhunt@google.com>2021-03-15 16:39:23 +0000
committerLibravatar Junio C Hamano <gitster@pobox.com>2021-03-17 10:00:20 -0700
commit097ea2c8486e9fc8c6c11bad8688434edeeda3f2 (patch)
treefef7231efd63627cdcc676e9fb73e053a487e287 /object.c
parentfsmonitor: refactor initialization of fsmonitor_last_update token (diff)
downloadtgif-097ea2c8486e9fc8c6c11bad8688434edeeda3f2.tar.xz
fsmonitor: avoid global-buffer-overflow READ when checking trivial response
query_result can be be an empty strbuf (STRBUF_INIT) - in that case trying to read 3 bytes triggers a buffer overflow read (as query_result.buf = '\0'). Therefore we need to check query_result's length before trying to read 3 bytes. This overflow was introduced in: 940b94f35c (fsmonitor: log invocation of FSMonitor hook to trace2, 2021-02-03) It was found when running the test-suite against ASAN, and can be most easily reproduced with the following command: make GIT_TEST_OPTS="-v" DEFAULT_TEST_TARGET="t7519-status-fsmonitor.sh" \ SANITIZE=address DEVELOPER=1 test ==2235==ERROR: AddressSanitizer: global-buffer-overflow on address 0x0000019e6e5e at pc 0x00000043745c bp 0x7fffd382c520 sp 0x7fffd382bcc8 READ of size 3 at 0x0000019e6e5e thread T0 #0 0x43745b in MemcmpInterceptorCommon(void*, int (*)(void const*, void const*, unsigned long), void const*, void const*, unsigned long) /home/abuild/rpmbuild/BUILD/llvm-11.0.0.src/build/../projects/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc:842:7 #1 0x43786d in bcmp /home/abuild/rpmbuild/BUILD/llvm-11.0.0.src/build/../projects/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc:887:10 #2 0x80b146 in fsmonitor_is_trivial_response /home/ahunt/oss-fuzz/git/fsmonitor.c:192:10 #3 0x80b146 in query_fsmonitor /home/ahunt/oss-fuzz/git/fsmonitor.c:175:7 #4 0x80a749 in refresh_fsmonitor /home/ahunt/oss-fuzz/git/fsmonitor.c:267:21 #5 0x80bad1 in tweak_fsmonitor /home/ahunt/oss-fuzz/git/fsmonitor.c:429:4 #6 0x90f040 in read_index_from /home/ahunt/oss-fuzz/git/read-cache.c:2321:3 #7 0x8e5d08 in repo_read_index_preload /home/ahunt/oss-fuzz/git/preload-index.c:164:15 #8 0x52dd45 in prepare_index /home/ahunt/oss-fuzz/git/builtin/commit.c:363:6 #9 0x52a188 in cmd_commit /home/ahunt/oss-fuzz/git/builtin/commit.c:1588:15 #10 0x4ce77e in run_builtin /home/ahunt/oss-fuzz/git/git.c:453:11 #11 0x4ccb18 in handle_builtin /home/ahunt/oss-fuzz/git/git.c:704:3 #12 0x4cb01c in run_argv /home/ahunt/oss-fuzz/git/git.c:771:4 #13 0x4cb01c in cmd_main /home/ahunt/oss-fuzz/git/git.c:902:19 #14 0x6aca8d in main /home/ahunt/oss-fuzz/git/common-main.c:52:11 #15 0x7fb027bf5349 in __libc_start_main (/lib64/libc.so.6+0x24349) #16 0x4206b9 in _start /home/abuild/rpmbuild/BUILD/glibc-2.26/csu/../sysdeps/x86_64/start.S:120 0x0000019e6e5e is located 2 bytes to the left of global variable 'strbuf_slopbuf' defined in 'strbuf.c:51:6' (0x19e6e60) of size 1 'strbuf_slopbuf' is ascii string '' 0x0000019e6e5e is located 126 bytes to the right of global variable 'signals' defined in 'sigchain.c:11:31' (0x19e6be0) of size 512 SUMMARY: AddressSanitizer: global-buffer-overflow /home/abuild/rpmbuild/BUILD/llvm-11.0.0.src/build/../projects/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc:842:7 in MemcmpInterceptorCommon(void*, int (*)(void const*, void const*, unsigned long), void const*, void const*, unsigned long) Shadow bytes around the buggy address: 0x000080334d70: f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9 00 00 00 00 0x000080334d80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x000080334d90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x000080334da0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x000080334db0: 00 00 00 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9 =>0x000080334dc0: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9[f9]01 f9 f9 f9 0x000080334dd0: f9 f9 f9 f9 03 f9 f9 f9 f9 f9 f9 f9 02 f9 f9 f9 0x000080334de0: f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9 04 f9 f9 f9 0x000080334df0: f9 f9 f9 f9 01 f9 f9 f9 f9 f9 f9 f9 00 00 00 00 0x000080334e00: f9 f9 f9 f9 00 00 00 00 f9 f9 f9 f9 01 f9 f9 f9 0x000080334e10: f9 f9 f9 f9 04 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9 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 Signed-off-by: Andrzej Hunt <ajrhunt@google.com> Acked-by: Jeff Hostetler <jeffhost@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'object.c')
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