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submodule add: sanity check existing .gitmodules

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"git submodule add" tries to find if a submodule with the same name
already exists at a different path, by looking up an entry in the
.gitmodules file.  If the entry in the file is incomplete, e.g.,
when the submodule.<name>.something variable is defined but there is
no definition of submodule.<name>.path variable, it accesses the
missing .path member of the submodule structure and triggers a
segfault.

A brief audit was done to make sure that the code does not assume
members other than those that are absolutely certain to exist: a
submodule obtained by submodule_from_name() should have .name
member, while a submodule obtained by submodule_from_path() should
also have .path as well as .name member, and we cannot assume
anything else.  Luckily, the module_add() codepath was the only
problematic one.  It is fairly recent code that comes from 1fa06ced
(submodule: prevent overwriting .gitmodules on path reuse,
2025-07-24).

A helper used by update_submodule() seems to assume that its call to
submodule_from_path() always yields a submodule object without a
failure, which seems to rely on the caller making sure it is the
case.  Leave an assert() with a NEEDSWORK comment there for future
developers to make sure the assumption actually holds.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Junio C Hamano
2025-11-15 23:02:57 -08:00
parent bb5c624209
commit dd8e8c786e
2 changed files with 29 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
builtin/submodule--helper.c
View File

@@ -1913,6 +1913,13 @@ static int determine_submodule_update_strategy(struct repository *r,
const char *val;
int ret;
/*
* NEEDSWORK: audit and ensure that update_submodule() has right
* to assume that submodule_from_path() above will always succeed.
*/
if (!sub)
BUG("update_submodule assumes a submodule exists at path (%s)",
path);
key = xstrfmt("submodule.%s.update", sub->name);
if (update) {
@@ -3537,14 +3544,15 @@ static int module_add(int argc, const char **argv, const char *prefix,
}
}
if(!add_data.sm_name)
if (!add_data.sm_name)
add_data.sm_name = add_data.sm_path;
existing = submodule_from_name(the_repository,
null_oid(the_hash_algo),
add_data.sm_name);
if (existing && strcmp(existing->path, add_data.sm_path)) {
if (existing && existing->path &&
strcmp(existing->path, add_data.sm_path)) {
if (!force) {
die(_("submodule name '%s' already used for path '%s'"),
add_data.sm_name, existing->path);

19
t/t7400-submodule-basic.sh
View File

@@ -48,6 +48,25 @@ test_expect_success 'submodule deinit works on empty repository' '
git submodule deinit --all
'
test_expect_success 'submodule add with incomplete .gitmodules' '
test_when_finished "rm -f expect actual" &&
test_when_finished "git config remove-section submodule.one" &&
test_when_finished "git rm -f one .gitmodules" &&
git init one &&
git -C one commit --allow-empty -m one-initial &&
git config -f .gitmodules submodule.one.ignore all &&
git submodule add ./one &&
for var in ignore path url
do
git config -f .gitmodules --get "submodule.one.$var" ||
return 1
done >actual &&
test_write_lines all one ./one >expect &&
test_cmp expect actual
'
test_expect_success 'setup - initial commit' '
>t &&
git add t &&