Hi, We found a stack read out-of-bounds parsing object files using git 2.10.0. It was tested on ArchLinux x86_64. To reproduce, first recompile git with ASAN support and then execute:
$ git init ; mkdir -p .git/objects/b2 ; printf 'x' > .git/objects/b2/93584ddd61af21260be75ee9f73e9d53f08cd0 Finally you can trigger the bug using several commands from git (other commands that parses all objects will work too), for instance: $ git fsck The ASAN report is here: ==2763==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffe16e4a690 at pc 0x0000006fe5dc bp 0x7ffe16e4a530 sp 0x7ffe16e4a520 READ of size 1 at 0x7ffe16e4a690 thread T0 #0 0x6fe5db in parse_sha1_header_extended /home/g/Work/Code/git-2.10.0/sha1_file.c:1684 #1 0x702cd4 in sha1_loose_object_info /home/g/Work/Code/git-2.10.0/sha1_file.c:2660 #2 0x70332c in sha1_object_info_extended /home/g/Work/Code/git-2.10.0/sha1_file.c:2696 #3 0x7038e0 in sha1_object_info /home/g/Work/Code/git-2.10.0/sha1_file.c:2745 #4 0x648498 in parse_object /home/g/Work/Code/git-2.10.0/object.c:260 #5 0x48d46d in fsck_sha1 builtin/fsck.c:367 #6 0x48da47 in fsck_loose builtin/fsck.c:493 #7 0x707514 in for_each_file_in_obj_subdir /home/g/Work/Code/git-2.10.0/sha1_file.c:3477 #8 0x70775b in for_each_loose_file_in_objdir_buf /home/g/Work/Code/git-2.10.0/sha1_file.c:3512 #9 0x707885 in for_each_loose_file_in_objdir /home/g/Work/Code/git-2.10.0/sha1_file.c:3532 #10 0x48dc1d in fsck_object_dir builtin/fsck.c:521 #11 0x48e2e6 in cmd_fsck builtin/fsck.c:644 #12 0x407a8f in run_builtin /home/g/Work/Code/git-2.10.0/git.c:352 #13 0x407e35 in handle_builtin /home/g/Work/Code/git-2.10.0/git.c:539 #14 0x408175 in run_argv /home/g/Work/Code/git-2.10.0/git.c:593 #15 0x408458 in cmd_main /home/g/Work/Code/git-2.10.0/git.c:665 #16 0x53fc70 in main /home/g/Work/Code/git-2.10.0/common-main.c:40 #17 0x7f0f46d43290 in __libc_start_main (/usr/lib/libc.so.6+0x20290) #18 0x405209 in _start (/home/g/Work/Code/git-2.10.0/git+0x405209) Address 0x7ffe16e4a690 is located in stack of thread T0 at offset 192 in frame #0 0x702834 in sha1_loose_object_info /home/g/Work/Code/git-2.10.0/sha1_file.c:2614 This frame has 5 object(s): [32, 40) 'mapsize' [96, 120) 'hdrbuf' [160, 192) 'hdr' <== Memory access at offset 192 overflows this variable [224, 368) 'st' [416, 576) 'stream' HINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext (longjmp and C++ exceptions *are* supported) SUMMARY: AddressSanitizer: stack-buffer-overflow /home/g/Work/Code/git-2.10.0/sha1_file.c:1684 in parse_sha1_header_extended Shadow bytes around the buggy address: 0x100042dc1480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x100042dc1490: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x100042dc14a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x100042dc14b0: 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 f4 0x100042dc14c0: f4 f4 f2 f2 f2 f2 00 00 00 f4 f2 f2 f2 f2 00 00 =>0x100042dc14d0: 00 00[f2]f2 f2 f2 00 00 00 00 00 00 00 00 00 00 0x100042dc14e0: 00 00 00 00 00 00 00 00 f4 f4 f2 f2 f2 f2 00 00 0x100042dc14f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x100042dc1500: 00 00 f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 0x100042dc1510: 00 00 00 00 f1 f1 f1 f1 04 f4 f4 f4 f2 f2 f2 f2 0x100042dc1520: 00 00 00 00 00 f4 f4 f4 f3 f3 f3 f3 00 00 00 00 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 Heap right redzone: fb Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack partial redzone: f4 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 Regards, Gustavo.