[PATCH 2/2] packfile: fix memory leak in add_delta_base_cache()

[Matheus Tavares <matheus.bernardino@usp.br>]

When add_delta_base_cache() is called with a base that is already in the
cache, no operation is performed. But the check is done after allocating
space for a new entry, so we end up leaking memory on the early return.
Also, the caller always expect that the base will be inserted, so it
never free()'s it. To fix both of these memory leaks, let's move the
allocation of a new entry further down in add_delta_base_cache(), and
make the function return an integer to indicate whether the insertion
was performed or not. Then, make the caller free() the base when needed.

Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
---
 packfile.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/packfile.c b/packfile.c
index 0319418d88..177793e01a 100644
--- a/packfile.c
+++ b/packfile.c
@@ -1471,10 +1471,10 @@ void clear_delta_base_cache(void)
 	}
 }
 
-static void add_delta_base_cache(struct packed_git *p, off_t base_offset,
+static int add_delta_base_cache(struct packed_git *p, off_t base_offset,
 	void *base, unsigned long base_size, enum object_type type)
 {
-	struct delta_base_cache_entry *ent = xmalloc(sizeof(*ent));
+	struct delta_base_cache_entry *ent;
 	struct list_head *lru, *tmp;
 
 	/*
@@ -1483,7 +1483,7 @@ static void add_delta_base_cache(struct packed_git *p, off_t base_offset,
 	 * and III might run concurrently across multiple threads).
 	 */
 	if (in_delta_base_cache(p, base_offset))
-		return;
+		return 0;
 
 	delta_base_cached += base_size;
 
@@ -1495,6 +1495,7 @@ static void add_delta_base_cache(struct packed_git *p, off_t base_offset,
 		release_delta_base_cache(f);
 	}
 
+	ent = xmalloc(sizeof(*ent));
 	ent->key.p = p;
 	ent->key.base_offset = base_offset;
 	ent->type = type;
@@ -1506,6 +1507,7 @@ static void add_delta_base_cache(struct packed_git *p, off_t base_offset,
 		hashmap_init(&delta_base_cache, delta_base_cache_hash_cmp, NULL, 0);
 	hashmap_entry_init(&ent->ent, pack_entry_hash(p, base_offset));
 	hashmap_add(&delta_base_cache, &ent->ent);
+	return 1;
 }
 
 int packed_object_info(struct repository *r, struct packed_git *p,
@@ -1841,8 +1843,10 @@ void *unpack_entry(struct repository *r, struct packed_git *p, off_t obj_offset,
 		 * thread could free() it (e.g. to make space for another entry)
 		 * before we are done using it.
 		 */
-		if (!external_base)
-			add_delta_base_cache(p, base_obj_offset, base, base_size, type);
+		if (!external_base && !add_delta_base_cache(p, base_obj_offset,
+						base, base_size, type)) {
+			free(base);
+		}
 
 		free(delta_data);
 		free(external_base);
-- 
2.28.0