diff mbox series

[v3,8/9] config API: add "string" version of *_value_multi(), fix segfaults

Message ID patch-v3-8.9-b45189b4624-20221125T093159Z-avarab@gmail.com (mailing list archive)
State New, archived
Headers show
Series config API: make "multi" safe, fix numerous segfaults | expand

Commit Message

Ævar Arnfjörð Bjarmason Nov. 25, 2022, 9:50 a.m. UTC 
Fix numerous and mostly long-standing segfaults in consumers of
the *_config_*value_multi() API. As discussed in the preceding commit
an empty key in the config syntax yields a "NULL" string, which these
users would give to strcmp() (or similar), resulting in segfaults.

As this change shows, most users users of the *_config_*value_multi()
API didn't really want such an an unsafe and low-level API, let's give
them something with the safety of git_config_get_string() instead.

This fix is similar to what the *_string() functions and others
acquired in[1] and [2]. Namely introducing and using a safer
"*_get_string_multi()" variant of the low-level "_*value_multi()"
function.

This fixes segfaults in code introduced in:

  - d811c8e17c6 (versionsort: support reorder prerelease suffixes, 2015-02-26)
  - c026557a373 (versioncmp: generalize version sort suffix reordering, 2016-12-08)
  - a086f921a72 (submodule: decouple url and submodule interest, 2017-03-17)
  - a6be5e6764a (log: add log.excludeDecoration config option, 2020-04-16)
  - 92156291ca8 (log: add default decoration filter, 2022-08-05)
  - 50a044f1e40 (gc: replace config subprocesses with API calls, 2022-09-27)

There are now three remaining files using the low-level API:

- Two cases in "builtin/submodule--helper.c", where it's used safely
  to see if any config exists.
- One in "builtin/for-each-repo.c", which we'll convert in a
  subsequent commit.
- The "t/helper/test-config.c" code added in [3].

As seen in the preceding commit we need to give the
"t/helper/test-config.c" caller these "NULL" entries.

We could also alter the underlying git_configset_get_value_multi()
function to be "string safe", but doing so would leave no room for
other variants of "*_get_value_multi()" that coerce to other types.

Such coercion can't be built on the string version, since as we've
established "NULL" is a true value in the boolean context, but if we
coerced it to "" for use in a list of strings it'll be subsequently
coerced to "false" as a boolean.

The callback pattern being used here will make it easy to introduce
e.g. a "multi" variant which coerces its values to "bool", "int",
"path" etc.

1. 40ea4ed9032 (Add config_error_nonbool() helper function,
   2008-02-11)
2. 6c47d0e8f39 (config.c: guard config parser from value=NULL,
   2008-02-11).
3. 4c715ebb96a (test-config: add tests for the config_set API,
   2014-07-28)

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 builtin/gc.c                   |  6 +++---
 builtin/log.c                  |  4 ++--
 config.c                       | 32 ++++++++++++++++++++++++++++++++
 config.h                       | 19 +++++++++++++++++++
 pack-bitmap.c                  |  2 +-
 submodule.c                    |  2 +-
 t/t4202-log.sh                 |  8 ++++++--
 t/t5310-pack-bitmaps.sh        |  8 ++++++--
 t/t7004-tag.sh                 |  9 +++++++--
 t/t7413-submodule-is-active.sh |  8 ++++++--
 t/t7900-maintenance.sh         | 22 +++++++++++++++++-----
 versioncmp.c                   |  4 ++--
 12 files changed, 102 insertions(+), 22 deletions(-)

Comments

Glen Choo Jan. 19, 2023, 1:03 a.m. UTC | #1 
Ævar Arnfjörð Bjarmason         <avarab@gmail.com> writes:

> Fix numerous and mostly long-standing segfaults in consumers of
> the *_config_*value_multi() API. As discussed in the preceding commit
> an empty key in the config syntax yields a "NULL" string, which these
> users would give to strcmp() (or similar), resulting in segfaults.
>
> As this change shows, most users users of the *_config_*value_multi()
> API didn't really want such an an unsafe and low-level API, let's give
> them something with the safety of git_config_get_string() instead.

I think the low-level API argument makes sense. All of the other
*_get_*() functions perform some kind of validation, e.g.
config_parse_*() for non-string types and config_error_nonbool() for
strings. In effect, *_get_value_multi() was returning raw output from
the config parser without any concern for the caller.

> This fix is similar to what the *_string() functions and others
> acquired in[1] and [2]. Namely introducing and using a safer
> "*_get_string_multi()" variant of the low-level "_*value_multi()"
> function.

This suggests to me that we should really get rid of
*_get_value_multi(), since nobody outside of config.c should need it. I
don't think we'd ever end up in a situation where the caller wants the
raw strings from the config parser (unless we had a config
key which accepted values of different types? but that sounds like a
terrible mistake).

> There are now three remaining files using the low-level API:
>
> - Two cases in "builtin/submodule--helper.c", where it's used safely
>   to see if any config exists.
> - One in "builtin/for-each-repo.c", which we'll convert in a
>   subsequent commit.
> - The "t/helper/test-config.c" code added in [3].

As you noted, the only remaining non-test caller of the low-level API is
builtin/submodule--helper.c, which maybe we could safely convert anyway
and get rid of the API altogether. I'm okay with that being a leftover
bit, but maybe that's worth noting in the CL.

> The callback pattern being used here will make it easy to introduce
> e.g. a "multi" variant which coerces its values to "bool", "int",
> "path" etc.

I like that this is quite easily extensible, e.g.

> diff --git a/config.c b/config.c
> index 0b07045ed8c..9bd43189c02 100644
> --- a/config.c
> +++ b/config.c
> @@ -2437,6 +2437,25 @@ int git_configset_get_value_multi(struct config_set *cs, const char *key,
>  	return 0;
>  }
>  
> +static int check_multi_string(struct string_list_item *item, void *util)
> +{
> +	return item->string ? 0 : config_error_nonbool(util);
> +}
> +
> +int git_configset_get_string_multi(struct config_set *cs, const char *key,
> +				   const struct string_list **dest)
> +{
> +	int ret;
> +
> +	if ((ret = git_configset_get_value_multi(cs, key, dest)))
> +		return ret;
> +	if ((ret = for_each_string_list((struct string_list *)*dest,
> +					check_multi_string, (void *)key)))
> +		return ret;
> +
> +	return 0;
> +}

we could just use config_parse_<typename>() if we want to add, e.g.
*_get_bool_multi().

And as a reasonableness check, config_error_nonbool() is what we use to
validate the *_get_string() functions, so it makes sense to reuse it for
the string list version.
diff mbox series

Patch

diff --git a/builtin/gc.c b/builtin/gc.c
index 69503e0a023..2d95c5b29aa 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -1513,7 +1513,7 @@  static int maintenance_register(int argc, const char **argv, const char *prefix)
 	else
 		git_config_set("maintenance.strategy", "incremental");
 
-	if (!git_config_get_value_multi(key, &list)) {
+	if (!git_config_get_string_multi(key, &list)) {
 		for_each_string_list_item(item, list) {
 			if (!strcmp(maintpath, item->string)) {
 				found = 1;
@@ -1581,8 +1581,8 @@  static int maintenance_unregister(int argc, const char **argv, const char *prefi
 		git_configset_add_file(&cs, config_file);
 	}
 	if (!(config_file
-	      ? git_configset_get_value_multi(&cs, key, &list)
-	      : git_config_get_value_multi(key, &list))) {
+	      ? git_configset_get_string_multi(&cs, key, &list)
+	      : git_config_get_string_multi(key, &list))) {
 		for_each_string_list_item(item, list) {
 			if (!strcmp(maintpath, item->string)) {
 				found = 1;
diff --git a/builtin/log.c b/builtin/log.c
index cc9d92f95da..cd17f311712 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -184,8 +184,8 @@  static void set_default_decoration_filter(struct decoration_filter *decoration_f
 	struct string_list *include = decoration_filter->include_ref_pattern;
 	const struct string_list *config_exclude;
 
-	if (!git_config_get_value_multi("log.excludeDecoration",
-					&config_exclude)) {
+	if (!git_config_get_string_multi("log.excludeDecoration",
+					 &config_exclude)) {
 		struct string_list_item *item;
 		for_each_string_list_item(item, config_exclude)
 			string_list_append(decoration_filter->exclude_ref_config_pattern,
diff --git a/config.c b/config.c
index 0b07045ed8c..9bd43189c02 100644
--- a/config.c
+++ b/config.c
@@ -2437,6 +2437,25 @@  int git_configset_get_value_multi(struct config_set *cs, const char *key,
 	return 0;
 }
 
+static int check_multi_string(struct string_list_item *item, void *util)
+{
+	return item->string ? 0 : config_error_nonbool(util);
+}
+
+int git_configset_get_string_multi(struct config_set *cs, const char *key,
+				   const struct string_list **dest)
+{
+	int ret;
+
+	if ((ret = git_configset_get_value_multi(cs, key, dest)))
+		return ret;
+	if ((ret = for_each_string_list((struct string_list *)*dest,
+					check_multi_string, (void *)key)))
+		return ret;
+
+	return 0;
+}
+
 int git_configset_get_string(struct config_set *cs, const char *key, char **dest)
 {
 	const char *value;
@@ -2587,6 +2606,13 @@  int repo_config_get_value_multi(struct repository *repo, const char *key,
 	return git_configset_get_value_multi(repo->config, key, dest);
 }
 
+int repo_config_get_string_multi(struct repository *repo, const char *key,
+				 const struct string_list **dest)
+{
+	git_config_check_init(repo);
+	return git_configset_get_string_multi(repo->config, key, dest);
+}
+
 int repo_config_get_string(struct repository *repo,
 			   const char *key, char **dest)
 {
@@ -2697,6 +2723,12 @@  int git_config_get_value_multi(const char *key, const struct string_list **dest)
 	return repo_config_get_value_multi(the_repository, key, dest);
 }
 
+int git_config_get_string_multi(const char *key,
+				const struct string_list **dest)
+{
+	return repo_config_get_string_multi(the_repository, key, dest);
+}
+
 int git_config_get_string(const char *key, char **dest)
 {
 	return repo_config_get_string(the_repository, key, dest);
diff --git a/config.h b/config.h
index 7f6ce6f2fb5..3079d60a860 100644
--- a/config.h
+++ b/config.h
@@ -472,6 +472,19 @@  RESULT_MUST_BE_USED
 int git_configset_get_value_multi(struct config_set *cs, const char *key,
 				  const struct string_list **dest);
 
+/**
+ * A validation wrapper for git_configset_get_value_multi() which does
+ * for it what git_configset_get_string() does for
+ * git_configset_get_value().
+ *
+ * The configuration syntax allows for "[section] key", which will
+ * give us a NULL entry in the "struct string_list", as opposed to
+ * "[section] key =" which is the empty string. Most users of the API
+ * are not prepared to handle NULL in a "struct string_list".
+ */
+int git_configset_get_string_multi(struct config_set *cs, const char *key,
+				   const struct string_list **dest);
+
 /**
  * Clears `config_set` structure, removes all saved variable-value pairs.
  */
@@ -507,6 +520,9 @@  int repo_config_get_value(struct repository *repo,
 RESULT_MUST_BE_USED
 int repo_config_get_value_multi(struct repository *repo, const char *key,
 				const struct string_list **dest);
+RESULT_MUST_BE_USED
+int repo_config_get_string_multi(struct repository *repo, const char *key,
+				 const struct string_list **dest);
 int repo_config_get_string(struct repository *repo,
 			   const char *key, char **dest);
 int repo_config_get_string_tmp(struct repository *repo,
@@ -561,6 +577,9 @@  int git_config_get_value(const char *key, const char **value);
 RESULT_MUST_BE_USED
 int git_config_get_value_multi(const char *key,
 			       const struct string_list **dest);
+RESULT_MUST_BE_USED
+int git_config_get_string_multi(const char *key,
+				const struct string_list **dest);
 
 /**
  * Resets and invalidates the config cache.
diff --git a/pack-bitmap.c b/pack-bitmap.c
index 81f0c0e016b..dd05ab03ca0 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -2303,7 +2303,7 @@  const struct string_list *bitmap_preferred_tips(struct repository *r)
 {
 	const struct string_list *dest;
 
-	if (!repo_config_get_value_multi(r, "pack.preferbitmaptips", &dest))
+	if (!repo_config_get_string_multi(r, "pack.preferbitmaptips", &dest))
 		return dest;
 	return NULL;
 }
diff --git a/submodule.c b/submodule.c
index e43c4230ba3..0f6cf864ed9 100644
--- a/submodule.c
+++ b/submodule.c
@@ -274,7 +274,7 @@  int is_tree_submodule_active(struct repository *repo,
 	free(key);
 
 	/* submodule.active is set */
-	if (!repo_config_get_value_multi(repo, "submodule.active", &sl)) {
+	if (!repo_config_get_string_multi(repo, "submodule.active", &sl)) {
 		struct pathspec ps;
 		struct strvec args = STRVEC_INIT;
 		const struct string_list_item *item;
diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index e4f02d8208b..ae73aef922f 100755
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh
@@ -835,7 +835,7 @@  test_expect_success 'log.decorate configuration' '
 
 '
 
-test_expect_failure 'parse log.excludeDecoration with no value' '
+test_expect_success 'parse log.excludeDecoration with no value' '
 	cp .git/config .git/config.orig &&
 	test_when_finished mv .git/config.orig .git/config &&
 
@@ -843,7 +843,11 @@  test_expect_failure 'parse log.excludeDecoration with no value' '
 	[log]
 		excludeDecoration
 	EOF
-	git log --decorate=short
+	cat >expect <<-\EOF &&
+	error: missing value for '\''log.excludeDecoration'\''
+	EOF
+	git log --decorate=short 2>actual &&
+	test_cmp expect actual
 '
 
 test_expect_success 'decorate-refs with glob' '
diff --git a/t/t5310-pack-bitmaps.sh b/t/t5310-pack-bitmaps.sh
index 2e65c8139c4..894c750080c 100755
--- a/t/t5310-pack-bitmaps.sh
+++ b/t/t5310-pack-bitmaps.sh
@@ -404,7 +404,7 @@  test_bitmap_cases () {
 		)
 	'
 
-	test_expect_failure 'pack.preferBitmapTips' '
+	test_expect_success 'pack.preferBitmapTips' '
 		git init repo &&
 		test_when_finished "rm -rf repo" &&
 		(
@@ -416,7 +416,11 @@  test_bitmap_cases () {
 			[pack]
 				preferBitmapTips
 			EOF
-			git repack -adb
+			cat >expect <<-\EOF &&
+			error: missing value for '\''pack.preferbitmaptips'\''
+			EOF
+			git repack -adb 2>actual &&
+			test_cmp expect actual
 		)
 	'
 
diff --git a/t/t7004-tag.sh b/t/t7004-tag.sh
index f343551a7d4..f4a31ada79a 100755
--- a/t/t7004-tag.sh
+++ b/t/t7004-tag.sh
@@ -1843,7 +1843,7 @@  test_expect_success 'invalid sort parameter in configuratoin' '
 	test_must_fail git tag -l "foo*"
 '
 
-test_expect_failure 'version sort handles empty value for versionsort.{prereleaseSuffix,suffix}' '
+test_expect_success 'version sort handles empty value for versionsort.{prereleaseSuffix,suffix}' '
 	cp .git/config .git/config.orig &&
 	test_when_finished mv .git/config.orig .git/config &&
 
@@ -1852,7 +1852,12 @@  test_expect_failure 'version sort handles empty value for versionsort.{prereleas
 		prereleaseSuffix
 		suffix
 	EOF
-	git tag -l --sort=version:refname
+	cat >expect <<-\EOF &&
+	error: missing value for '\''versionsort.suffix'\''
+	error: missing value for '\''versionsort.prereleasesuffix'\''
+	EOF
+	git tag -l --sort=version:refname 2>actual &&
+	test_cmp expect actual
 '
 
 test_expect_success 'version sort with prerelease reordering' '
diff --git a/t/t7413-submodule-is-active.sh b/t/t7413-submodule-is-active.sh
index bfe27e50732..887d181b72e 100755
--- a/t/t7413-submodule-is-active.sh
+++ b/t/t7413-submodule-is-active.sh
@@ -51,7 +51,7 @@  test_expect_success 'is-active works with submodule.<name>.active config' '
 	test-tool -C super submodule is-active sub1
 '
 
-test_expect_failure 'is-active handles submodule.active config missing a value' '
+test_expect_success 'is-active handles submodule.active config missing a value' '
 	cp super/.git/config super/.git/config.orig &&
 	test_when_finished mv super/.git/config.orig super/.git/config &&
 
@@ -60,7 +60,11 @@  test_expect_failure 'is-active handles submodule.active config missing a value'
 		active
 	EOF
 
-	test-tool -C super submodule is-active sub1
+	cat >expect <<-\EOF &&
+	error: missing value for '\''submodule.active'\''
+	EOF
+	test-tool -C super submodule is-active sub1 2>actual &&
+	test_cmp expect actual
 '
 
 test_expect_success 'is-active works with basic submodule.active config' '
diff --git a/t/t7900-maintenance.sh b/t/t7900-maintenance.sh
index 2dbac07be83..487e326b3fa 100755
--- a/t/t7900-maintenance.sh
+++ b/t/t7900-maintenance.sh
@@ -524,7 +524,7 @@  test_expect_success 'register and unregister' '
 	git maintenance unregister --config-file ./other --force
 '
 
-test_expect_failure 'register with no value for maintenance.repo' '
+test_expect_success 'register with no value for maintenance.repo' '
 	cp .git/config .git/config.orig &&
 	test_when_finished mv .git/config.orig .git/config &&
 
@@ -532,10 +532,15 @@  test_expect_failure 'register with no value for maintenance.repo' '
 	[maintenance]
 		repo
 	EOF
-	git maintenance register
+	cat >expect <<-\EOF &&
+	error: missing value for '\''maintenance.repo'\''
+	EOF
+	git maintenance register 2>actual &&
+	test_cmp expect actual &&
+	git config maintenance.repo
 '
 
-test_expect_failure 'unregister with no value for maintenance.repo' '
+test_expect_success 'unregister with no value for maintenance.repo' '
 	cp .git/config .git/config.orig &&
 	test_when_finished mv .git/config.orig .git/config &&
 
@@ -546,8 +551,15 @@  test_expect_failure 'unregister with no value for maintenance.repo' '
 	cat >expect <<-\EOF &&
 	error: missing value for '\''maintenance.repo'\''
 	EOF
-	git maintenance unregister &&
-	git maintenance unregister --force
+	test_expect_code 128 git maintenance unregister 2>actual.raw &&
+	grep ^error actual.raw >actual &&
+	test_cmp expect actual &&
+	git config maintenance.repo &&
+
+	git maintenance unregister --force 2>actual.raw &&
+	grep ^error actual.raw >actual &&
+	test_cmp expect actual &&
+	git config maintenance.repo
 '
 
 test_expect_success !MINGW 'register and unregister with regex metacharacters' '
diff --git a/versioncmp.c b/versioncmp.c
index 60c3a517122..7498da96e0e 100644
--- a/versioncmp.c
+++ b/versioncmp.c
@@ -164,8 +164,8 @@  int versioncmp(const char *s1, const char *s2)
 		const char *const oldk = "versionsort.prereleasesuffix";
 		const struct string_list *newl;
 		const struct string_list *oldl;
-		int new = git_config_get_value_multi(newk, &newl);
-		int old = git_config_get_value_multi(oldk, &oldl);
+		int new = git_config_get_string_multi(newk, &newl);
+		int old = git_config_get_string_multi(oldk, &oldl);
 
 		if (!new && !old)
 			warning("ignoring %s because %s is set", oldk, newk);