mirrors/git
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

midx: bounds-check large offset chunk

Browse Source 
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>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King
2023-10-09 17:05:30 -04:00
committed by Junio C Hamano
parent 0924869b4e
commit 2abd56e9b2
3 changed files with 26 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
midx.c
View File

@ -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;