commit-graph: close file before returning NULL

From: =?UTF-8?q?Kleber=20Tarc=C3=ADsio?= <[email protected]>

There are two reasons that we could return NULL early within load_commit_graph_chain():

1. The file does not exist, so the file pointer is NULL.
2. The file exists, but is too small to contain a single hash.

These were grouped together when the function was first written in 5c84b3396 (commit-graph: load commit-graph chains, 2019-06-18) in order to simplify how the 'chain_name' string is freed. However, the current code leaves a narrow window where the file pointer is not closed when the file exists, but is rejected for being too small.

Split out these cases separately to ensure we close the file in this case.

Signed-off-by Kleber Tarcísio <[email protected]>

Signed-off-by Derrick Stolee <[email protected]>

---
commit-graph: close file before returning NULL

This change was originally submitted to the microsoft/git fork [1]. Kleber discovered this issue using some automated tool they are working on. We recommended that this change be submitted to the core Git group, but we have not had any word from the original author in some time. Hence, I am submitting it on their behalf.

 commit-graph.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

commit-graph.c +6 -3

index 441b36016ba..06107beedcb 100644
@@ -523,10 +523,13 @@ static struct commit_graph *load_commit_graph_chain(struct repository *r,
 	stat_res = stat(chain_name, &st);
 	free(chain_name);
 
-	if (!fp ||
-	    stat_res ||
-	    st.st_size <= the_hash_algo->hexsz)
+	if (!fp)
 		return NULL;
+	if (stat_res ||
+	    st.st_size <= the_hash_algo->hexsz) {
+		fclose(fp);
+		return NULL;
+	}
 
 	count = st.st_size / (the_hash_algo->hexsz + 1);
 	CALLOC_ARRAY(oids, count);

base-commit: ab1f2765f78e75ee51dface57e1071b3b7f42b09