From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: "Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>
Cc: christian.couder@gmail.com, git@vger.kernel.org,
gitster@pobox.com, luke@diamand.org, newren@gmail.com
Subject: Re: [PATCH v2] read-cache.c: fix writing "link" index ext with null base oid
Date: Wed, 13 Feb 2019 13:14:52 +0100 [thread overview]
Message-ID: <87imxnkhqb.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <20190213095129.31272-1-pclouds@gmail.com>
On Wed, Feb 13 2019, Nguyễn Thái Ngọc Duy wrote:
> Since commit 7db118303a (unpack_trees: fix breakage when o->src_index !=
> o->dst_index - 2018-04-23) and changes in merge code to use separate
> index_state for source and destination, when doing a merge with split
> index activated, we may run into this line in unpack_trees():
>
> o->result.split_index = init_split_index(&o->result);
>
> This is by itself not wrong. But this split index information is not
> fully populated (and it's only so when move_cache_to_base_index() is
> called, aka force splitting the index, or loading index_state from a
> file). Both "base_oid" and "base" in this case remain null.
>
> So when writing the main index down, we link to this index with null
> oid (default value after init_split_index()), which also means "no split
> index" internally. This triggers an incorrect base index refresh:
>
> warning: could not freshen shared index '.../sharedindex.0{40}'
>
> This patch makes sure we will not refresh null base_oid (because the
> file is never there). It also makes sure not to write "link" extension
> with null base_oid in the first place (no point having it at
> all). Read code already has protection against null base_oid.
>
> There is also another side fix in remove_split_index() that causes a
> crash when doing "git update-index --no-split-index" when base_oid in
> the index file is null. In this case we will not load
> istate->split_index->base but we dereference it anyway and are rewarded
> with a segfault. This should not happen anymore, but it's still wrong to
> dereference a potential NULL pointer, especially when we do check for
> NULL pointer in the next code.
>
> Reported-by: Luke Diamand <luke@diamand.org>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
> v2 added a new test
This round looks good to me. Passes all tests with/without
GIT_TEST_SPLIT_INDEX=true
> read-cache.c | 5 +++--
> split-index.c | 34 ++++++++++++++++++----------------
> t/t1700-split-index.sh | 18 ++++++++++++++++++
> 3 files changed, 39 insertions(+), 18 deletions(-)
>
> diff --git a/read-cache.c b/read-cache.c
> index 8f644f68b4..d140b44f8f 100644
> --- a/read-cache.c
> +++ b/read-cache.c
> @@ -2520,7 +2520,8 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
> return err;
>
> /* Write extension data here */
> - if (!strip_extensions && istate->split_index) {
> + if (!strip_extensions && istate->split_index &&
> + !is_null_oid(&istate->split_index->base_oid)) {
> struct strbuf sb = STRBUF_INIT;
>
> err = write_link_extension(&sb, istate) < 0 ||
However, it looks like you based this on a pre-2.20.0 version of
git. This conflicts with read-cache.c earlier than 3b1d9e045e ("eoie:
add End of Index Entry (EOIE) extension", 2018-10-10).
I fixed that manually, and pushed it out to github.com/avar/git.git
duy-read-cache-null-split-index-fix, that's what I've tested on top of
current "master".
next prev parent reply other threads:[~2019-02-13 12:15 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-06 10:25 could not freshen shared index ..../sharedindex.0000000000000000000000000000000000000000' Luke Diamand
2019-02-06 13:17 ` Christian Couder
2019-02-08 10:02 ` Duy Nguyen
2019-02-08 16:38 ` Luke Diamand
2019-02-09 5:00 ` Duy Nguyen
2019-02-09 9:57 ` Luke Diamand
2019-02-09 10:36 ` Duy Nguyen
2019-02-09 11:23 ` [PATCH] unpack-trees.c: fix writing "link" index ext with null base oid Nguyễn Thái Ngọc Duy
2019-02-09 14:14 ` Luke Diamand
2019-02-12 5:43 ` Elijah Newren
2019-02-12 16:49 ` Junio C Hamano
2019-02-12 9:36 ` Ævar Arnfjörð Bjarmason
2019-02-13 9:51 ` [PATCH v2] read-cache.c: " Nguyễn Thái Ngọc Duy
2019-02-13 12:14 ` Ævar Arnfjörð Bjarmason [this message]
2019-02-08 17:23 ` could not freshen shared index ..../sharedindex.0000000000000000000000000000000000000000' Junio C Hamano
2019-02-09 4:56 ` Duy Nguyen
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