midx: report checksum mismatches during 'verify'

'git multi-pack-index verify' inspects the data in an existing MIDX for
correctness by checking that the recorded object offsets are correct,
and so on.

But it does not check that the file's trailing checksum matches the data
that it records. So, if an on-disk corruption happened to occur in the
final few bytes (and all other data was recorded correctly), we would:

  - get a clean result from 'git multi-pack-index verify', but
  - be unable to reuse the existing MIDX when writing a new one (since
    we now check for checksum mismatches before reusing a MIDX)

Teach the 'verify' sub-command to recognize corruption in the checksum
by calling midx_checksum_valid().

Suggested-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Taylor Blau 2021-06-23 14:39:15 -04:00 committed by Junio C Hamano
parent ec1e28ef9c
commit f89ecf7988
2 changed files with 8 additions and 0 deletions

3
midx.c
View File

@ -1228,6 +1228,9 @@ int verify_midx_file(struct repository *r, const char *object_dir, unsigned flag
return result;
}
if (!midx_checksum_valid(m))
midx_report(_("incorrect checksum"));
if (flags & MIDX_PROGRESS)
progress = start_delayed_progress(_("Looking for referenced packfiles"),
m->num_packs);

View File

@ -418,6 +418,11 @@ test_expect_success 'corrupt MIDX is not reused' '
git multi-pack-index verify
'
test_expect_success 'verify incorrect checksum' '
pos=$(($(wc -c <$objdir/pack/multi-pack-index) - 1)) &&
corrupt_midx_and_verify $pos "\377" $objdir "incorrect checksum"
'
test_expect_success 'repack progress off for redirected stderr' '
GIT_PROGRESS_DELAY=0 git multi-pack-index --object-dir=$objdir repack 2>err &&
test_line_count = 0 err