Subject: Re: [PATCH] config: remove unneeded struct field

From: Junio C Hamano <[email-masked]>
Date: Thu, 17 Jul 2025 10:31:32 -0700

Phillip Wood <[email-masked]> writes:

> I stumbled across this use-after-free while working on the deprecation
> of core.commentChar=auto.

And that other topic also adds more uses of "is kvi->path set?", so
we'd need a bit of semantic conflict resolution, which was fun ;-)

FYI, here is what I'd be using as merge-fix, a change that would be
squashed in when the named branch is merged in.

I expect that this part would change a lot anyway, to make it fail
when "auto" is used under WITH_BREAKING_CHANGES, so the conflict
resolution for the current/previous round may not matter all that
much.

--- >8 ---
Subject: [PATCH] merge-fix/pw/3.0-commentchar-auto-deprecation

Conflicts with pw/config-kvi-remove-path that removes kvi->path
field.  Checking if kvi->path is set should be done by inspecting
kvi->origin_type and seeing if it is CONFIG_ORIGIN_FILE instead, and
otherwise kvi->filename is usable when it is CONFIG_ORIGIN_FILE.
---
 builtin/commit.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/builtin/commit.c b/builtin/commit.c
index a513709a51..04440fbd3f 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -771,10 +771,10 @@ static int comment_char_config_cb(const char *key, const char *value,
 		return 0;
 
 	cfg->last_key_id = key_id;
-	if (!kvi->path) {
+	if (kvi->origin_type != CONFIG_ORIGIN_FILE) {
 		return 0;
-	} else if (get_comment_key_flags(cfg, kvi->path, key_id)) {
-		set_comment_key_flags(cfg, kvi->path, key_id, KEY_SEEN_TWICE);
+	} else if (get_comment_key_flags(cfg, kvi->filename, key_id)) {
+		set_comment_key_flags(cfg, kvi->filename, key_id, KEY_SEEN_TWICE);
 	} else {
 		struct comment_char_cfg_item *item;
 
@@ -782,8 +782,8 @@ static int comment_char_config_cb(const char *key, const char *value,
 		item = &cfg->item[cfg->nr - 1];
 		item->key_id = key_id;
 		item->scope = kvi->scope;
-		item->path = xstrdup(kvi->path);
-		set_comment_key_flags(cfg, kvi->path, key_id, KEY_SEEN_ONCE);
+		item->path = xstrdup(kvi->filename);
+		set_comment_key_flags(cfg, kvi->filename, key_id, KEY_SEEN_ONCE);
 	}
 	cfg->auto_set_in_file =	value && !strcmp(value, "auto");
 
-- 
2.50.1-441-gd7f68e2bd5