Fix segfault if gitmodules is invalid

The reload_all call could end up dereferencing a NULL pointer if
there was an error while attempting to load the submodules config
data (i.e. invalid content in the gitmodules file).  This fixes it.

Author: arrbee

include/git2/submodule.h

@@ -115,8 +115,8 @@ typedef enum {
  *
  * - The submodule is not mentioned in the HEAD, the index, and the config,
  *   but does "exist" in the working directory (i.e. there is a subdirectory
- *   that is a valid self-contained git repo).  In this case, this function
- *   returns GIT_EEXISTS to indicate the the submodule exists but not in a
+ *   that appears to be a Git repository).  In this case, this function
+ *   returns GIT_EEXISTS to indicate a sub-repository exists but not in a
  *   state where a git_submodule can be instantiated.
  * - The submodule is not mentioned in the HEAD, index, or config and the
  *   working directory doesn't contain a value git repo at that path.
@@ -129,7 +129,7 @@ typedef enum {
  * @param repo The parent repository
  * @param name The name of or path to the submodule; trailing slashes okay
  * @return 0 on success, GIT_ENOTFOUND if submodule does not exist,
- *         GIT_EEXISTS if submodule exists in working directory only,
+ *         GIT_EEXISTS if a repository is found in working directory only,
  *         -1 on other errors.
  */
 GIT_EXTERN(int) git_submodule_lookup(

src/submodule.c

@@ -156,7 +156,7 @@ int git_submodule_lookup(
 			if (git_buf_joinpath(&path, git_repository_workdir(repo), name) < 0)
 				return -1;
 
-			if (git_path_contains_dir(&path, DOT_GIT))
+			if (git_path_contains(&path, DOT_GIT))
 				error = GIT_EEXISTS;
 
 			git_buf_free(&path);
@@ -846,7 +846,8 @@ int git_submodule_reload_all(git_repository *repo, int force)
 	if (repo->submodules)
 		git_strmap_foreach_value(repo->submodules, sm, { sm->flags = 0; });
 
-	error = load_submodule_config(repo, true);
+	if ((error = load_submodule_config(repo, true)) < 0)
+		return error;
 
 	git_strmap_foreach_value(repo->submodules, sm, {
 		git_strmap *cache = repo->submodules;

tests/submodule/nosubs.c

@@ -0,0 +1,95 @@
+/* test the submodule APIs on repositories where there are no submodules */
+
+#include "clar_libgit2.h"
+#include "posix.h"
+
+void test_submodule_nosubs__cleanup(void)
+{
+	cl_git_sandbox_cleanup();
+}
+
+void test_submodule_nosubs__lookup(void)
+{
+	git_repository *repo = cl_git_sandbox_init("status");
+	git_submodule *sm = NULL;
+
+	p_mkdir("status/subrepo", 0777);
+	cl_git_mkfile("status/subrepo/.git", "gitdir: ../.git");
+
+	cl_assert_equal_i(GIT_ENOTFOUND, git_submodule_lookup(&sm, repo, "subdir"));
+
+	cl_assert_equal_i(GIT_EEXISTS, git_submodule_lookup(&sm, repo, "subrepo"));
+
+	cl_git_pass(git_submodule_reload_all(repo, 0));
+
+	cl_assert_equal_i(GIT_ENOTFOUND, git_submodule_lookup(&sm, repo, "subdir"));
+
+	cl_assert_equal_i(GIT_EEXISTS, git_submodule_lookup(&sm, repo, "subrepo"));
+}
+
+void test_submodule_nosubs__immediate_reload(void)
+{
+	git_repository *repo = cl_git_sandbox_init("status");
+	cl_git_pass(git_submodule_reload_all(repo, 0));
+}
+
+static int fake_submod_cb(git_submodule *sm, const char *n, void *p)
+{
+	GIT_UNUSED(sm); GIT_UNUSED(n); GIT_UNUSED(p);
+	return 0;
+}
+
+void test_submodule_nosubs__foreach(void)
+{
+	git_repository *repo = cl_git_sandbox_init("status");
+	cl_git_pass(git_submodule_foreach(repo, fake_submod_cb, NULL));
+}
+
+void test_submodule_nosubs__add(void)
+{
+	git_repository *repo = cl_git_sandbox_init("status");
+	git_submodule *sm, *sm2;
+
+	cl_git_pass(git_submodule_add_setup(&sm, repo, "https://github.com/libgit2/libgit2.git", "submodules/libgit2", 1));
+
+	cl_git_pass(git_submodule_lookup(&sm2, repo, "submodules/libgit2"));
+	git_submodule_free(sm2);
+
+	cl_git_pass(git_submodule_foreach(repo, fake_submod_cb, NULL));
+	cl_git_pass(git_submodule_reload_all(repo, 0));
+
+	git_submodule_free(sm);
+}
+
+void test_submodule_nosubs__reload_add_reload(void)
+{
+	git_repository *repo = cl_git_sandbox_init("status");
+	git_submodule *sm;
+
+	cl_git_pass(git_submodule_reload_all(repo, 0));
+
+	cl_git_pass(git_submodule_add_setup(&sm, repo, "https://github.com/libgit2/libgit2.git", "submodules/libgit2", 1));
+
+	cl_git_pass(git_submodule_reload_all(repo, 0));
+
+	cl_assert_equal_s("submodules/libgit2", git_submodule_name(sm));
+	git_submodule_free(sm);
+
+	cl_git_pass(git_submodule_lookup(&sm, repo, "submodules/libgit2"));
+	cl_assert_equal_s("submodules/libgit2", git_submodule_name(sm));
+	git_submodule_free(sm);
+}
+
+void test_submodule_nosubs__bad_gitmodules(void)
+{
+	git_repository *repo = cl_git_sandbox_init("status");
+
+	cl_git_mkfile("status/.gitmodules", "[submodule \"foobar\"]\tpath=blargle\n\turl=\n\tbranch=\n\tupdate=flooble\n\n");
+	cl_git_fail(git_submodule_reload_all(repo, 0));
+
+	cl_git_rewritefile("status/.gitmodules", "[submodule \"foobar\"]\tpath=blargle\n\turl=\n\tbranch=\n\tupdate=rebase\n\n");
+	cl_git_pass(git_submodule_reload_all(repo, 0));
+
+	cl_git_pass(git_submodule_lookup(NULL, repo, "foobar"));
+	cl_assert_equal_i(GIT_ENOTFOUND, git_submodule_lookup(NULL, repo, "subdir"));
+}