[PATCH] fsmonitor: fix khash memory leak in do_handle_client

From: Paul Tarjan via GitGitGadget <gitgitgadget@gmail.com>
Date: Dec 30, 2025, 12:42 UTC
Message-ID: <pull.2148.git.git.1767098576384.gitgitgadget@gmail.com>

From: Paul Tarjan <github@paulisageek.com>

The do_handle_client() function allocates a khash table to de-duplicate pathnames when responding to client requests. Two issues existed:

1. kh_release_str() was used instead of kh_destroy_str(). The release
   function only frees internal arrays (flags, keys, vals) but not the
   struct itself (allocated by kh_init_str via xcalloc). This caused a
   40-byte leak per request.

2. The khash was freed mid-function rather than in the cleanup section,
   so if the worker thread was interrupted before reaching that point
   during daemon shutdown, the memory would leak.

Fix both issues by:
- Initializing shown = NULL at declaration
- Using kh_destroy_str() which handles NULL and frees both internal
  arrays and the struct itself
- Moving the cleanup to the cleanup section so it runs on all exit paths

Signed-off-by: Claude <claude@anthropic.com>
---
    fsmonitor: fix khash memory leak in do_handle_client
    
    The do_handle_client() function allocates a khash table to de-duplicate
    pathnames when responding to client requests. Two issues existed:
    
     1. kh_release_str() was used instead of kh_destroy_str(). The release
        function only frees internal arrays (flags, keys, vals) but not the
        struct itself (allocated by kh_init_str via xcalloc). This caused a
        40-byte leak per request.
    
     2. The khash was freed mid-function rather than in the cleanup section,
        so if the worker thread was interrupted before reaching that point
        during daemon shutdown, the memory would leak.
    
    Fix both issues by:
    
     * Initializing shown = NULL at declaration
     * Using kh_destroy_str() which handles NULL and frees both internal
       arrays and the struct itself
     * Moving the cleanup to the cleanup section so it runs on all exit
       paths

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2148%2Fptarjan%2Fclaude%2Ffix-fsmonitor-hashmap-leak-gfDCU-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2148/ptarjan/claude/fix-fsmonitor-hashmap-leak-gfDCU-v1
Pull-Request: https://github.com/git/git/pull/2148

 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);

base-commit: 7c7698a654a7a0031f65b0ab0c1c4e438e95df60

-- 
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