builtin/sparse-checkout: fix leaking sanitized patterns

Both `git sparse-checkout add` and `git sparse-checkout set` accept a
list of additional directories or patterns. These get massaged via calls
to `sanitize_paths()`, which may end up modifying the passed-in array by
updating its pointers to be prefixed paths. This allocates memory that
we never free.

Refactor the code to instead use a `struct strvec`, which makes it way
easier for us to track the lifetime correctly. The couple of extra
memory allocations likely do not matter as we only ever populate it with
command line arguments.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

builtin/sparse-checkout.c

@@ -669,7 +669,7 @@ static void add_patterns_literal(int argc, const char **argv,
 	add_patterns_from_input(pl, argc, argv, use_stdin ? stdin : NULL);
 }
 
-static int modify_pattern_list(int argc, const char **argv, int use_stdin,
+static int modify_pattern_list(struct strvec *args, int use_stdin,
 			       enum modify_type m)
 {
 	int result;
@@ -679,13 +679,13 @@ static int modify_pattern_list(int argc, const char **argv, int use_stdin,
 	switch (m) {
 	case ADD:
 		if (core_sparse_checkout_cone)
-			add_patterns_cone_mode(argc, argv, pl, use_stdin);
+			add_patterns_cone_mode(args->nr, args->v, pl, use_stdin);
 		else
-			add_patterns_literal(argc, argv, pl, use_stdin);
+			add_patterns_literal(args->nr, args->v, pl, use_stdin);
 		break;
 
 	case REPLACE:
-		add_patterns_from_input(pl, argc, argv,
+		add_patterns_from_input(pl, args->nr, args->v,
 					use_stdin ? stdin : NULL);
 		break;
 	}
@@ -706,12 +706,12 @@ static int modify_pattern_list(int argc, const char **argv, int use_stdin,
 	return result;
 }
 
-static void sanitize_paths(int argc, const char **argv,
+static void sanitize_paths(struct strvec *args,
 			   const char *prefix, int skip_checks)
 {
 	int i;
 
-	if (!argc)
+	if (!args->nr)
 		return;
 
 	if (prefix && *prefix && core_sparse_checkout_cone) {
@@ -721,8 +721,11 @@ static void sanitize_paths(int argc, const char **argv,
 		 */
 		int prefix_len = strlen(prefix);
 
-		for (i = 0; i < argc; i++)
-			argv[i] = prefix_path(prefix, prefix_len, argv[i]);
+		for (i = 0; i < args->nr; i++) {
+			char *prefixed_path = prefix_path(prefix, prefix_len, args->v[i]);
+			strvec_replace(args, i, prefixed_path);
+			free(prefixed_path);
+		}
 	}
 
 	if (skip_checks)
@@ -732,20 +735,20 @@ static void sanitize_paths(int argc, const char **argv,
 		die(_("please run from the toplevel directory in non-cone mode"));
 
 	if (core_sparse_checkout_cone) {
-		for (i = 0; i < argc; i++) {
-			if (argv[i][0] == '/')
+		for (i = 0; i < args->nr; i++) {
+			if (args->v[i][0] == '/')
 				die(_("specify directories rather than patterns (no leading slash)"));
-			if (argv[i][0] == '!')
+			if (args->v[i][0] == '!')
 				die(_("specify directories rather than patterns.  If your directory starts with a '!', pass --skip-checks"));
-			if (strpbrk(argv[i], "*?[]"))
+			if (strpbrk(args->v[i], "*?[]"))
 				die(_("specify directories rather than patterns.  If your directory really has any of '*?[]\\' in it, pass --skip-checks"));
 		}
 	}
 
-	for (i = 0; i < argc; i++) {
+	for (i = 0; i < args->nr; i++) {
 		struct cache_entry *ce;
 		struct index_state *index = the_repository->index;
-		int pos = index_name_pos(index, argv[i], strlen(argv[i]));
+		int pos = index_name_pos(index, args->v[i], strlen(args->v[i]));
 
 		if (pos < 0)
 			continue;
@@ -754,9 +757,9 @@ static void sanitize_paths(int argc, const char **argv,
 			continue;
 
 		if (core_sparse_checkout_cone)
-			die(_("'%s' is not a directory; to treat it as a directory anyway, rerun with --skip-checks"), argv[i]);
+			die(_("'%s' is not a directory; to treat it as a directory anyway, rerun with --skip-checks"), args->v[i]);
 		else
-			warning(_("pass a leading slash before paths such as '%s' if you want a single file (see NON-CONE PROBLEMS in the git-sparse-checkout manual)."), argv[i]);
+			warning(_("pass a leading slash before paths such as '%s' if you want a single file (see NON-CONE PROBLEMS in the git-sparse-checkout manual)."), args->v[i]);
 	}
 }
 
@@ -780,6 +783,8 @@ static int sparse_checkout_add(int argc, const char **argv, const char *prefix)
 			 N_("read patterns from standard in")),
 		OPT_END(),
 	};
+	struct strvec patterns = STRVEC_INIT;
+	int ret;
 
 	setup_work_tree();
 	if (!core_apply_sparse_checkout)
@@ -791,9 +796,14 @@ static int sparse_checkout_add(int argc, const char **argv, const char *prefix)
 			     builtin_sparse_checkout_add_options,
 			     builtin_sparse_checkout_add_usage, 0);
 
-	sanitize_paths(argc, argv, prefix, add_opts.skip_checks);
+	for (int i = 0; i < argc; i++)
+		strvec_push(&patterns, argv[i]);
+	sanitize_paths(&patterns, prefix, add_opts.skip_checks);
 
-	return modify_pattern_list(argc, argv, add_opts.use_stdin, ADD);
+	ret = modify_pattern_list(&patterns, add_opts.use_stdin, ADD);
+
+	strvec_clear(&patterns);
+	return ret;
 }
 
 static char const * const builtin_sparse_checkout_set_usage[] = {
@@ -826,6 +836,8 @@ static int sparse_checkout_set(int argc, const char **argv, const char *prefix)
 			   PARSE_OPT_NONEG),
 		OPT_END(),
 	};
+	struct strvec patterns = STRVEC_INIT;
+	int ret;
 
 	setup_work_tree();
 	repo_read_index(the_repository);
@@ -846,13 +858,18 @@ static int sparse_checkout_set(int argc, const char **argv, const char *prefix)
 	 * top-level directory (much as 'init' would do).
 	 */
 	if (!core_sparse_checkout_cone && !set_opts.use_stdin && argc == 0) {
-		argv = default_patterns;
-		argc = default_patterns_nr;
+		for (int i = 0; i < default_patterns_nr; i++)
+			strvec_push(&patterns, default_patterns[i]);
 	} else {
-		sanitize_paths(argc, argv, prefix, set_opts.skip_checks);
+		for (int i = 0; i < argc; i++)
+			strvec_push(&patterns, argv[i]);
+		sanitize_paths(&patterns, prefix, set_opts.skip_checks);
 	}
 
-	return modify_pattern_list(argc, argv, set_opts.use_stdin, REPLACE);
+	ret = modify_pattern_list(&patterns, set_opts.use_stdin, REPLACE);
+
+	strvec_clear(&patterns);
+	return ret;
 }
 
 static char const * const builtin_sparse_checkout_reapply_usage[] = {