Subject: [PATCH v12 01/13] fsmonitor: fix khash memory leak in do_handle_client

From: "Paul Tarjan via GitGitGadget" <[email-masked]>
Date: Tue, 31 Mar 2026 06:19:06 +0000

From: Paul Tarjan <[email-masked]>

The `shown` kh_str_t was freed with kh_release_str() at a point in
the code only reachable in the non-trivial response path.  When the
client receives a trivial response, the code jumps to the `cleanup`
label, skipping the kh_release_str() call entirely and leaking the
hash table.

Fix this by initializing `shown` to NULL and moving the cleanup to the
`cleanup` label using kh_destroy_str(), which is safe to call on NULL.
This ensures the hash table is freed regardless of which code path is
taken.

Signed-off-by: Paul Tarjan <[email-masked]>
---
 builtin/fsmonitor--daemon.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/builtin/fsmonitor--daemon.c b/builtin/fsmonitor--daemon.c
index 242c594646..bc4571938c 100644
--- a/builtin/fsmonitor--daemon.c
+++ b/builtin/fsmonitor--daemon.c
@@ -671,7 +671,7 @@ static int do_handle_client(struct fsmonitor_daemon_state *state,
 	const struct fsmonitor_batch *batch;
 	struct fsmonitor_batch *remainder = NULL;
 	intmax_t count = 0, duplicates = 0;
-	kh_str_t *shown;
+	kh_str_t *shown = NULL;
 	int hash_ret;
 	int do_trivial = 0;
 	int do_flush = 0;
@@ -909,8 +909,6 @@ static int do_handle_client(struct fsmonitor_daemon_state *state,
 		total_response_len += payload.len;
 	}
 
-	kh_release_str(shown);
-
 	pthread_mutex_lock(&state->main_lock);
 
 	if (token_data->client_ref_count > 0)
@@ -954,6 +952,7 @@ static int do_handle_client(struct fsmonitor_daemon_state *state,
 	trace2_data_intmax("fsmonitor", the_repository, "response/count/duplicates", duplicates);
 
 cleanup:
+	kh_destroy_str(shown);
 	strbuf_release(&response_token);
 	strbuf_release(&requested_token_id);
 	strbuf_release(&payload);
-- 
gitgitgadget