object-file: free(*contents) only in read_loose_object() caller

In the preceding commit a free() of uninitialized memory regression in
96e41f5 (fsck: report invalid object type-path combinations,
2021-10-01) was fixed, but we'd still have an issue with leaking
memory from fsck_loose(). Let's fix that issue too.

That issue was introduced in my 31deb28 (fsck: don't hard die on
invalid object types, 2021-10-01). It can be reproduced under
SANITIZE=leak with the test I added in 093fffd (fsck tests: add
test for fsck-ing an unknown type, 2021-10-01):

    ./t1450-fsck.sh --run=84 -vixd

In some sense it's not a problem, we lost the same amount of memory in
terms of things malloc'd and not free'd. It just moved from the "still
reachable" to "definitely lost" column in valgrind(1) nomenclature[1],
since we'd have die()'d before.

But now that we don't hard die() anymore in the library let's properly
free() it. Doing so makes this code much easier to follow, since we'll
now have one function owning the freeing of the "contents" variable,
not two.

For context on that memory management pattern the read_loose_object()
function was added in f6371f9 (sha1_file: add read_loose_object()
function, 2017-01-13) and subsequently used in c68b489 (fsck:
parse loose object paths directly, 2017-01-13). The pattern of it
being the task of both sides to free() the memory has been there in
this form since its inception.

1. https://valgrind.org/docs/manual/mc-manual.html#mc-manual.leaks

Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

builtin/fsck.c

@@ -604,7 +604,7 @@ static int fsck_loose(const struct object_id *oid, const char *path, void *data)
 	struct object *obj;
 	enum object_type type = OBJ_NONE;
 	unsigned long size;
-	void *contents;
+	void *contents = NULL;
 	int eaten;
 	struct object_info oi = OBJECT_INFO_INIT;
 	struct object_id real_oid = *null_oid();
@@ -629,6 +629,7 @@ static int fsck_loose(const struct object_id *oid, const char *path, void *data)
 			    path);
 	if (err < 0) {
 		errors_found |= ERROR_OBJECT;
+		free(contents);
 		return 0; /* keep checking other objects */
 	}
 

object-file.c

@@ -2533,8 +2533,6 @@ int read_loose_object(const char *path,
 	char hdr[MAX_HEADER_LEN];
 	unsigned long *size = oi->sizep;
 
-	*contents = NULL;
-
 	map = map_loose_object_1(the_repository, path, NULL, &mapsize);
 	if (!map) {
 		error_errno(_("unable to mmap %s"), path);
@@ -2564,10 +2562,9 @@ int read_loose_object(const char *path,
 			goto out;
 		}
 		if (check_object_signature(the_repository, expected_oid,
-					   *contents, *size, oi->type_name->buf, real_oid)) {
-			free(*contents);
+					   *contents, *size,
+					   oi->type_name->buf, real_oid))
 			goto out;
-		}
 	}
 
 	ret = 0; /* everything checks out */