From: "Martin Ågren" <martin.agren@gmail.com>
To: Git Mailing List <git@vger.kernel.org>
Cc: "brian m. carlson" <sandals@crustytoothpaste.net>,
Junio C Hamano <gitster@pobox.com>
Subject: Re: What's cooking in git.git (Jan 2019, #01; Mon, 7)
Date: Wed, 9 Jan 2019 22:06:08 +0100 [thread overview]
Message-ID: <CAN0heSqLUWpwRdeUvYj2KnDX-QxSOnWOdKWz77RjHKJ3AFUGEQ@mail.gmail.com> (raw)
In-Reply-To: <CAN0heSoRYYS3-UAamE9nibhORPoD+_TRHu5-ZTeYxYMS4BAnrA@mail.gmail.com>
On Wed, 9 Jan 2019 at 08:37, Martin Ågren <martin.agren@gmail.com> wrote:
>
> On Tue, 8 Jan 2019 at 00:34, Junio C Hamano <gitster@pobox.com> wrote:
> > * bc/sha-256 (2018-11-14) 12 commits
> > - hash: add an SHA-256 implementation using OpenSSL
> > - sha256: add an SHA-256 implementation using libgcrypt
> > - Add a base implementation of SHA-256 support
> > - commit-graph: convert to using the_hash_algo
> > - t/helper: add a test helper to compute hash speed
> > - sha1-file: add a constant for hash block size
> > - t: make the sha1 test-tool helper generic
> > - t: add basic tests for our SHA-1 implementation
> > - cache: make hashcmp and hasheq work with larger hashes
> > - hex: introduce functions to print arbitrary hashes
> > - sha1-file: provide functions to look up hash algorithms
> > - sha1-file: rename algorithm to "sha1"
> >
> > Add sha-256 hash and plug it through the code to allow building Git
> > with the "NewHash".
>
> AddressSanitizer barks at current pu (855f98be272f19d16564e) for a
> handful of tests.
>
> One example is t5702-protocol-v2.sh. [...]
>
> ==1691823==ERROR: AddressSanitizer: heap-buffer-overflow on address
> 0x6040000004f2 at pc 0x0000004ea0fd bp 0x7ffc53082590 sp
> 0x7ffc53081d40
> READ of size 32 at 0x6040000004f2 thread T0
> #0 0x4ea0fc in __asan_memcpy
> llvm/projects/compiler-rt/lib/asan/asan_interceptors_memintrinsics.cc:23
> #1 0x8603ec in oidset_insert oidset.c
> #2 0x86c977 in add_promisor_object packfile.c:2129:4
> #3 0x86c07a in for_each_object_in_pack packfile.c:2070:7
> #4 0x86c535 in for_each_packed_object packfile.c:2095:7
> #5 0x86c651 in is_promisor_object packfile.c:2151:4
> 0x6040000004f2 is located 0 bytes to the right of 34-byte region
> [0x6040000004d0,0x6040000004f2)
> allocated by thread T0 here:
> #0 0x4eb4cf in malloc
> llvm/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:146
> #1 0x9fa1db in do_xmalloc wrapper.c:60:8
> #2 0x9fa2fd in do_xmallocz wrapper.c:100:8
> #3 0x9fa2fd in xmallocz_gently wrapper.c:113
> #4 0x86a877 in unpack_compressed_entry packfile.c:1588:11
> #5 0x86a02e in unpack_entry packfile.c:1737:11
> #6 0x867431 in cache_or_unpack_entry packfile.c:1439:10
> #7 0x867431 in packed_object_info packfile.c:1506
> #8 0x96b7be in oid_object_info_extended sha1-file.c:1394:10
> #9 0x96d7d0 in read_object sha1-file.c:1434:6
> #10 0x96d7d0 in read_object_file_extended sha1-file.c:1476
> #11 0x85cf40 in repo_read_object_file ./object-store.h:174:9
> #12 0x85cf40 in parse_object object.c:273
> #13 0x86c752 in add_promisor_object packfile.c:2108:23
> #14 0x86c07a in for_each_object_in_pack packfile.c:2070:7
> #15 0x86c535 in for_each_packed_object packfile.c:2095:7
> #16 0x86c651 in is_promisor_object packfile.c:2151:4
I found some more time to look into this.
It seems we have a buffer with raw data and we set up a `struct
object_id *` pointing into it, at a (supposed) OID value. Then
`update_tree_entry_internal()` verifies that the buffer contains
sufficiently many bytes, i.e., at least `the_hash_algo->rawsz` (=20).
We immediately call `oidset_insert()` which copies an entire struct,
i.e., we copy sizeof(struct object_id) (=32) bytes. Which is 12 more
than what is known to be safe. For this particular input data, we read
outside allocated memory.
I can think of three possible approaches:
* Allocate with a margin (GIT_MAX_RAWSZ - the_hash_algo->rawsz) where
"necessary" (TM). Maybe not so maintainable.
* Teach `oidset_insert()` (i.e., khash) to only copy
`the_hash_algo->rawsz` bytes. Maybe not so good for performance.
* Ignore.
I wonder which of these is the least awful, or if there are other ideas.
Martin
next prev parent reply other threads:[~2019-01-09 21:06 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-07 23:34 What's cooking in git.git (Jan 2019, #01; Mon, 7) Junio C Hamano
2019-01-08 9:50 ` tg/checkout-no-overlay, was " Thomas Gummerer
2019-01-08 17:51 ` Junio C Hamano
2019-01-08 17:30 ` ag/sequencer-reduce-rewriting-todo " Alban Gruin
2019-01-08 21:20 ` sb/more-repo-in-api, was " Jonathan Tan
2019-01-08 21:35 ` Junio C Hamano
2019-01-09 21:28 ` Stefan Beller
2019-01-09 7:37 ` Martin Ågren
2019-01-09 21:06 ` Martin Ågren [this message]
2019-01-10 1:02 ` brian m. carlson
2019-01-10 18:55 ` Junio C Hamano
2019-01-10 19:03 ` Martin Ågren
2019-01-10 4:25 ` [PATCH 0/5] tree-walk object_id refactor brian m. carlson
2019-01-10 4:25 ` [PATCH 1/5] tree-walk: copy object ID before use brian m. carlson
2019-01-10 4:25 ` [PATCH 2/5] match-trees: compute buffer offset correctly when splicing brian m. carlson
2019-01-10 4:25 ` [PATCH 3/5] match-trees: use hashcpy to splice trees brian m. carlson
2019-01-10 6:45 ` Jeff King
2019-01-10 23:55 ` brian m. carlson
2019-01-11 14:51 ` Jeff King
2019-01-11 14:54 ` Jeff King
2019-01-14 1:30 ` brian m. carlson
2019-01-14 15:40 ` Jeff King
2019-01-10 4:25 ` [PATCH 4/5] tree-walk: store object_id in a separate member brian m. carlson
2019-01-10 6:49 ` Jeff King
2019-01-10 23:57 ` brian m. carlson
2019-01-10 4:25 ` [PATCH 5/5] cache: make oidcpy always copy GIT_MAX_RAWSZ bytes brian m. carlson
2019-01-10 6:50 ` Jeff King
2019-01-10 6:40 ` [PATCH 0/5] tree-walk object_id refactor Jeff King
2019-01-11 0:17 ` brian m. carlson
2019-01-11 14:17 ` Jeff King
2019-01-15 0:39 ` [PATCH v2 " brian m. carlson
2019-01-15 0:39 ` [PATCH v2 1/5] tree-walk: copy object ID before use brian m. carlson
2019-01-15 0:39 ` [PATCH v2 2/5] match-trees: compute buffer offset correctly when splicing brian m. carlson
2019-01-15 0:39 ` [PATCH v2 3/5] match-trees: use hashcpy to splice trees brian m. carlson
2019-01-15 0:39 ` [PATCH v2 4/5] tree-walk: store object_id in a separate member brian m. carlson
2019-01-15 0:39 ` [PATCH v2 5/5] cache: make oidcpy always copy GIT_MAX_RAWSZ bytes brian m. carlson
2019-01-15 17:51 ` [PATCH v2 0/5] tree-walk object_id refactor Junio C Hamano
2019-01-09 10:28 ` What's cooking in git.git (Jan 2019, #01; Mon, 7) Jeff King
2019-01-10 19:05 ` Junio C Hamano
2019-01-10 19:46 ` Junio C Hamano
2019-01-10 18:02 ` Stefan Beller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAN0heSqLUWpwRdeUvYj2KnDX-QxSOnWOdKWz77RjHKJ3AFUGEQ@mail.gmail.com \
--to=martin.agren@gmail.com \
--cc=git@vger.kernel.org \
--cc=gitster@pobox.com \
--cc=sandals@crustytoothpaste.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).