From: Jeff King <peff@peff.net>
To: git@vger.kernel.org
Cc: Taylor Blau <me@ttaylorr.com>
Subject: [PATCH 10/20] midx: bounds-check large offset chunk
Date: Mon, 9 Oct 2023 17:05:30 -0400 [thread overview]
Message-ID: <20231009210530.GJ3282181@coredump.intra.peff.net> (raw)
In-Reply-To: <20231009205544.GA3281950@coredump.intra.peff.net>
When we see a large offset bit in the regular midx offset table, we
use the entry as an index into a separate large offset table (just like
a pack idx does). But we don't bounds-check the access to that large
offset table (nor even record its size when we parse the chunk!).
The equivalent code for a regular pack idx is in check_pack_index_ptr().
But things are a bit simpler here because of the chunked format: we can
just check our array index directly.
As a bonus, we can get rid of the st_mult() here. If our array
bounds-check is successful, then we know that the result will fit in a
size_t (and the bounds check uses a division to avoid overflow
entirely).
Signed-off-by: Jeff King <peff@peff.net>
---
midx.c | 8 +++++---
midx.h | 1 +
t/t5319-multi-pack-index.sh | 20 ++++++++++++++++++++
3 files changed, 26 insertions(+), 3 deletions(-)
diff --git a/midx.c b/midx.c
index 7b1b45f381..3e768d0df0 100644
--- a/midx.c
+++ b/midx.c
@@ -180,7 +180,8 @@ struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local
if (read_chunk(cf, MIDX_CHUNKID_OBJECTOFFSETS, midx_read_object_offsets, m))
die(_("multi-pack-index required object offsets chunk missing or corrupted"));
- pair_chunk_unsafe(cf, MIDX_CHUNKID_LARGEOFFSETS, &m->chunk_large_offsets);
+ pair_chunk(cf, MIDX_CHUNKID_LARGEOFFSETS, &m->chunk_large_offsets,
+ &m->chunk_large_offsets_len);
if (git_env_bool("GIT_TEST_MIDX_READ_RIDX", 1))
pair_chunk_unsafe(cf, MIDX_CHUNKID_REVINDEX, &m->chunk_revindex);
@@ -303,8 +304,9 @@ off_t nth_midxed_offset(struct multi_pack_index *m, uint32_t pos)
die(_("multi-pack-index stores a 64-bit offset, but off_t is too small"));
offset32 ^= MIDX_LARGE_OFFSET_NEEDED;
- return get_be64(m->chunk_large_offsets +
- st_mult(sizeof(uint64_t), offset32));
+ if (offset32 >= m->chunk_large_offsets_len / sizeof(uint64_t))
+ die(_("multi-pack-index large offset out of bounds"));
+ return get_be64(m->chunk_large_offsets + sizeof(uint64_t) * offset32);
}
return offset32;
diff --git a/midx.h b/midx.h
index 5b2a7da043..e8e8884d16 100644
--- a/midx.h
+++ b/midx.h
@@ -37,6 +37,7 @@ struct multi_pack_index {
const unsigned char *chunk_oid_lookup;
const unsigned char *chunk_object_offsets;
const unsigned char *chunk_large_offsets;
+ size_t chunk_large_offsets_len;
const unsigned char *chunk_revindex;
const char **pack_names;
diff --git a/t/t5319-multi-pack-index.sh b/t/t5319-multi-pack-index.sh
index 30687d5452..16050f39d9 100755
--- a/t/t5319-multi-pack-index.sh
+++ b/t/t5319-multi-pack-index.sh
@@ -1118,4 +1118,24 @@ test_expect_success 'reader notices too-small object offset chunk' '
test_cmp expect err
'
+test_expect_success 'reader bounds-checks large offset table' '
+ # re-use the objects64 dir here to cheaply get access to a midx
+ # with large offsets.
+ git init repo &&
+ test_when_finished "rm -rf repo" &&
+ (
+ cd repo &&
+ (cd ../objects64 && pwd) >.git/objects/info/alternates &&
+ git multi-pack-index --object-dir=../objects64 write &&
+ midx=../objects64/pack/multi-pack-index &&
+ corrupt_chunk_file $midx LOFF clear &&
+ test_must_fail git cat-file \
+ --batch-check --batch-all-objects 2>err &&
+ cat >expect <<-\EOF &&
+ fatal: multi-pack-index large offset out of bounds
+ EOF
+ test_cmp expect err
+ )
+'
+
test_done
--
2.42.0.884.g35e1fe1a6a
next prev parent reply other threads:[~2023-10-09 21:05 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-09 20:55 [PATCH 0/20] bounds-checks for chunk-based files Jeff King
2023-10-09 20:58 ` [PATCH 01/20] chunk-format: note that pair_chunk() is unsafe Jeff King
2023-10-10 23:45 ` Taylor Blau
2023-10-11 22:49 ` Jeff King
2023-10-09 20:58 ` [PATCH 02/20] t: add library for munging chunk-format files Jeff King
2023-10-10 23:47 ` Taylor Blau
2023-10-09 20:59 ` [PATCH 03/20] midx: stop ignoring malformed oid fanout chunk Jeff King
2023-10-10 23:50 ` Taylor Blau
2023-10-11 22:52 ` Jeff King
2023-10-09 20:59 ` [PATCH 04/20] commit-graph: check size of " Jeff King
2023-10-11 0:08 ` Taylor Blau
2023-10-11 1:24 ` Taylor Blau
2023-10-11 23:01 ` Jeff King
2023-10-09 21:02 ` [PATCH 05/20] midx: check size of oid lookup chunk Jeff King
2023-10-09 21:04 ` [PATCH 06/20] commit-graph: check consistency of fanout table Jeff King
2023-10-11 14:45 ` Taylor Blau
2023-10-09 21:05 ` [PATCH 07/20] midx: check size of pack names chunk Jeff King
2023-10-11 14:52 ` Taylor Blau
2023-10-11 23:06 ` Jeff King
2023-10-09 21:05 ` [PATCH 08/20] midx: enforce chunk alignment on reading Jeff King
2023-10-11 14:56 ` Taylor Blau
2023-10-11 15:01 ` Taylor Blau
2023-10-11 23:09 ` Jeff King
2023-10-09 21:05 ` [PATCH 09/20] midx: check size of object offset chunk Jeff King
2023-10-11 18:31 ` Taylor Blau
2023-10-09 21:05 ` Jeff King [this message]
2023-10-11 18:38 ` [PATCH 10/20] midx: bounds-check large " Taylor Blau
2023-10-11 23:18 ` Jeff King
2023-10-09 21:05 ` [PATCH 11/20] midx: check size of revindex chunk Jeff King
2023-10-11 18:41 ` Taylor Blau
2023-10-09 21:05 ` [PATCH 12/20] commit-graph: check size of commit data chunk Jeff King
2023-10-11 18:46 ` Taylor Blau
2023-10-11 23:22 ` Jeff King
2023-10-09 21:05 ` [PATCH 13/20] commit-graph: detect out-of-bounds extra-edges pointers Jeff King
2023-10-11 19:02 ` Taylor Blau
2023-10-09 21:05 ` [PATCH 14/20] commit-graph: bounds-check base graphs chunk Jeff King
2023-10-11 19:05 ` Taylor Blau
2023-10-09 21:05 ` [PATCH 15/20] commit-graph: check size of generations chunk Jeff King
2023-10-09 21:05 ` [PATCH 16/20] commit-graph: bounds-check generation overflow chunk Jeff King
2023-10-09 21:05 ` [PATCH 17/20] commit-graph: check bounds when accessing BDAT chunk Jeff King
2023-10-11 19:11 ` Taylor Blau
2023-10-11 23:27 ` Jeff King
2023-10-09 21:05 ` [PATCH 18/20] commit-graph: check bounds when accessing BIDX chunk Jeff King
2023-10-11 19:15 ` Taylor Blau
2023-10-09 21:05 ` [PATCH 19/20] commit-graph: detect out-of-order BIDX offsets Jeff King
2023-10-11 19:16 ` Taylor Blau
2023-10-09 21:06 ` [PATCH 20/20] chunk-format: drop pair_chunk_unsafe() Jeff King
2023-10-11 19:19 ` [PATCH 0/20] bounds-checks for chunk-based files Taylor Blau
2023-10-11 23:31 ` Jeff King
2023-10-13 19:25 ` [PATCH 0/8] chunk-format: introduce `pair_chunk_expect()` convenience API Taylor Blau
2023-10-13 19:25 ` [PATCH 1/8] chunk-format: introduce `pair_chunk_expect()` helper Taylor Blau
2023-10-13 19:25 ` [PATCH 2/8] commit-graph: read `OIDF` chunk with `pair_chunk_expect()` Taylor Blau
2023-10-13 19:25 ` [PATCH 3/8] commit-graph: read `CDAT` " Taylor Blau
2023-10-13 19:25 ` [PATCH 4/8] commit-graph: read `GDAT` " Taylor Blau
2023-10-13 19:25 ` [PATCH 5/8] commit-graph: read `BIDX` " Taylor Blau
2023-10-13 19:49 ` Taylor Blau
2023-10-14 16:10 ` Junio C Hamano
2023-10-20 10:31 ` Jeff King
2023-10-13 19:25 ` [PATCH 6/8] midx: read `OIDF` " Taylor Blau
2023-10-13 21:04 ` Junio C Hamano
2023-10-13 19:25 ` [PATCH 7/8] midx: read `OIDL` " Taylor Blau
2023-10-13 19:25 ` [PATCH 8/8] midx: read `OOFF` " Taylor Blau
2023-10-20 10:23 ` [PATCH 0/8] chunk-format: introduce `pair_chunk_expect()` convenience API Jeff King
2023-10-14 0:43 ` [PATCH 21/20] t5319: make corrupted large-offset test more robust Jeff King
2023-10-14 19:42 ` Junio C Hamano
2023-10-15 3:17 ` Jeff King
2023-10-15 17:04 ` Junio C Hamano
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