[PATCH v2] read-cache.c: fix writing "link" index ext with null base oid
- From
Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
- Date
- Feb 13, 2019, 09:51 UTC
- Message-ID
- <20190213095129.31272-1-pclouds@gmail.com>
- In-Reply-To
- <20190209112328.26317-1-pclouds@gmail.com>
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
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 || @@ -2794,7 +2795,7 @@ int write_locked_index(struct index_state *istate, struct lock_file *lock, ret = write_split_index(istate, lock, flags); /* Freshen the shared index only if the split-index was written */ - if (!ret && !new_shared_index) { + if (!ret && !new_shared_index && !is_null_oid(&si->base_oid)) { const char *shared_index = git_path("sharedindex.%s", oid_to_hex(&si->base_oid)); freshen_shared_index(shared_index, 1); diff --git a/split-index.c b/split-index.c index 5820412dc5..a9d13611a4 100644 --- a/split-index.c +++ b/split-index.c @@ -440,24 +440,26 @@ void add_split_index(struct index_state *istate) void remove_split_index(struct index_state *istate) { if (istate->split_index) { - /* - * When removing the split index, we need to move - * ownership of the mem_pool associated with the - * base index to the main index. There may be cache entries - * allocated from the base's memory pool that are shared with - * the_index.cache[]. - */ - mem_pool_combine(istate->ce_mem_pool, istate->split_index->base->ce_mem_pool); + if (istate->split_index->base) { + /* + * When removing the split index, we need to move + * ownership of the mem_pool associated with the + * base index to the main index. There may be cache entries + * allocated from the base's memory pool that are shared with + * the_index.cache[]. + */ + mem_pool_combine(istate->ce_mem_pool, + istate->split_index->base->ce_mem_pool); - /* - * The split index no longer owns the mem_pool backing - * its cache array. As we are discarding this index, - * mark the index as having no cache entries, so it - * will not attempt to clean up the cache entries or - * validate them. - */ - if (istate->split_index->base) + /* + * The split index no longer owns the mem_pool backing + * its cache array. As we are discarding this index, + * mark the index as having no cache entries, so it + * will not attempt to clean up the cache entries or + * validate them. + */ istate->split_index->base->cache_nr = 0; + } /* * We can discard the split index because its diff --git a/t/t1700-split-index.sh b/t/t1700-split-index.sh index f053bf83eb..ea5181aff9 100755 --- a/t/t1700-split-index.sh +++ b/t/t1700-split-index.sh @@ -447,4 +447,22 @@ test_expect_success 'writing split index with null sha1 does not write cache tre test_line_count = 0 cache-tree.out ' +test_expect_success 'do not refresh null base index' ' + test_create_repo merge && + ( + cd merge && + test_commit initial && + git checkout -b side-branch && + test_commit extra && + git checkout master && + git update-index --split-index && + test_commit more && + # must not write a new shareindex, or we wont catch the problem + git -c splitIndex.maxPercentChange=100 merge --no-edit side-branch 2>err && + # i.e. do not expect warnings like + # could not freshen shared index .../shareindex.00000... + test_must_be_empty err + ) +' + test_done
-- 2.21.0.rc0.328.g0e39304f8d