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The "log" reftable block stores reflog information. This information is
compressed using zlib. The inflated size is stored in the block header
so that callers can easily learn ahead of time how large of a buffer
they have to allocate to inflate the data in a single pass. So to
reconstruct the full inflated block we:
- Copy over the header as-is, as it's not deflated.
- Append the inflated data to the buffer.
The inflated block size stored in the header also includes the length of
the header itself. So to figure out the bytes that should be inflated by
zlib we need to subtract the header size, which is trusted data, from
the block size, which is untrusted data derived from the block header.
While we do verify that we were able to inflate all data as expected, we
don't verify ahead of time that the encoded block length is larger than
the header length. This can lead to an underflow, which makes zlib
assume that it can write more data into the target buffer than we have
allocated. The result is an out-of-bounds write:
==1422297==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7c1ff6de5231 at pc 0x55555579a628 bp 0x7fffffff4f10 sp 0x7fffffff46d0
WRITE of size 4 at 0x7c1ff6de5231 thread T0
#0 0x55555579a627 in __asan_memcpy (./build/t/unit-tests+0x246627)
#1 0x55555598b093 in reftable_block_init ./build/../reftable/block.c:277:3
#2 0x555555813701 in test_reftable_block__corrupt_log_block_size ./build/../t/unit-tests/u-reftable-block.c:495:20
#3 0x5555557f684e in clar_run_test ./build/../t/unit-tests/clar/clar.c:335:3
#4 0x5555557f2e69 in clar_run_suite ./build/../t/unit-tests/clar/clar.c:431:3
#5 0x5555557f2882 in clar_test_run ./build/../t/unit-tests/clar/clar.c:636:4
#6 0x5555557f375f in clar_test ./build/../t/unit-tests/clar/clar.c:687:11
#7 0x5555557fa49d in cmd_main ./build/../t/unit-tests/unit-test.c:62:8
#8 0x55555584af4a in main ./build/../common-main.c:9:11
#9 0x7ffff7a2b284 in __libc_start_call_main (/nix/store/57iz36553175g3178pvxjij8z5rcsd4n-glibc-2.42-61/lib/libc.so.6+0x2b284) (BuildId: 8ae0b698f2d4e727f569f64bb166e08ae30bd077)
#10 0x7ffff7a2b337 in __libc_start_main@GLIBC_2.2.5 (/nix/store/57iz36553175g3178pvxjij8z5rcsd4n-glibc-2.42-61/lib/libc.so.6+0x2b337) (BuildId: 8ae0b698f2d4e727f569f64bb166e08ae30bd077)
#11 0x555555694c24 in _start (./build/t/unit-tests+0x140c24)
0x7c1ff6de5231 is located 0 bytes after 1-byte region [0x7c1ff6de5230,0x7c1ff6de5231)
allocated by thread T0 here:
#0 0x55555579db1b in realloc.part.0 asan_malloc_linux.cpp.o
#1 0x5555559868d7 in reftable_realloc ./build/../reftable/basics.c:36:9
#2 0x55555598a98f in reftable_alloc_grow ./build/../reftable/basics.h:229:10
#3 0x55555598ae58 in reftable_block_init ./build/../reftable/block.c:269:3
#4 0x555555813701 in test_reftable_block__corrupt_log_block_size ./build/../t/unit-tests/u-reftable-block.c:495:20
#5 0x5555557f684e in clar_run_test ./build/../t/unit-tests/clar/clar.c:335:3
#6 0x5555557f2e69 in clar_run_suite ./build/../t/unit-tests/clar/clar.c:431:3
#7 0x5555557f2882 in clar_test_run ./build/../t/unit-tests/clar/clar.c:636:4
#8 0x5555557f375f in clar_test ./build/../t/unit-tests/clar/clar.c:687:11
#9 0x5555557fa49d in cmd_main ./build/../t/unit-tests/unit-test.c:62:8
#10 0x55555584af4a in main ./build/../common-main.c:9:11
#11 0x7ffff7a2b284 in __libc_start_call_main (/nix/store/57iz36553175g3178pvxjij8z5rcsd4n-glibc-2.42-61/lib/libc.so.6+0x2b284) (BuildId: 8ae0b698f2d4e727f569f64bb166e08ae30bd077)
#12 0x7ffff7a2b337 in __libc_start_main@GLIBC_2.2.5 (/nix/store/57iz36553175g3178pvxjij8z5rcsd4n-glibc-2.42-61/lib/libc.so.6+0x2b337) (BuildId: 8ae0b698f2d4e727f569f64bb166e08ae30bd077)
#13 0x555555694c24 in _start (./build/t/unit-tests+0x140c24)
SUMMARY: AddressSanitizer: heap-buffer-overflow (./build/t/unit-tests+0x246627) in __asan_memcpy
Shadow bytes around the buggy address:
0x7c1ff6de4f80: fa fa fd fd fa fa fd fd fa fa fd fd fa fa fd fd
0x7c1ff6de5000: fa fa fd fd fa fa fd fd fa fa fd fd fa fa fd fd
0x7c1ff6de5080: fa fa fd fd fa fa fd fd fa fa fd fd fa fa fd fd
0x7c1ff6de5100: fa fa fd fd fa fa fd fd fa fa fd fd fa fa fd fd
0x7c1ff6de5180: fa fa fd fd fa fa fd fd fa fa fd fa fa fa fd fd
=>0x7c1ff6de5200: fa fa 04 fa fa fa[01]fa fa fa fa fa fa fa fa fa
0x7c1ff6de5280: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x7c1ff6de5300: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x7c1ff6de5380: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x7c1ff6de5400: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x7c1ff6de5480: 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
Fix the bug by adding a sanity check and add a unit test.
Reported-by: oxsignal <awo@kakao.com>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an unusually rich command set that provides both high-level operations and full access to internals.
Git is an Open Source project covered by the GNU General Public License version 2 (some parts of it are under different licenses, compatible with the GPLv2). It was originally written by Linus Torvalds with help of a group of hackers around the net.
Please read the file INSTALL for installation instructions.
Many Git online resources are accessible from https://git-scm.com/ including full documentation and Git related tools.
See Documentation/gittutorial.adoc to get started, then see
Documentation/giteveryday.adoc for a useful minimum set of commands, and
Documentation/git-<commandname>.adoc for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
documentation of each command with man git-<commandname> or git help <commandname>.
CVS users may also want to read Documentation/gitcvs-migration.adoc
(man gitcvs-migration or git help cvs-migration if git is
installed).
The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org (read Documentation/SubmittingPatches for instructions on patch submission and Documentation/CodingGuidelines).
Those wishing to help with error message, usage and informational message
string translations (localization l10) should see po/README.md
(a po file is a Portable Object file that holds the translations).
To subscribe to the list, send an email to git+subscribe@vger.kernel.org (see https://subspace.kernel.org/subscribing.html for details). The mailing list archives are available at https://lore.kernel.org/git/, https://marc.info/?l=git and other archival sites.
Issues which are security relevant should be disclosed privately to the Git Security mailing list git-security@googlegroups.com.
The maintainer frequently sends the "What's cooking" reports that list the current status of various development topics to the mailing list. The discussion following them give a good reference for project status, development direction and remaining tasks.
The name "git" was given by Linus Torvalds when he wrote the very first version. He described the tool as "the stupid content tracker" and the name as (depending on your mood):
- random three-letter combination that is pronounceable, and not actually used by any common UNIX command. The fact that it is a mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the dictionary of slang.
- "global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks