Subject: [PATCH v2 2/3] pack-bitmap: fix memory leak if `load_bitmap_entries_v1` failed

From: "Taylor Blau via GitGitGadget" <[email-masked]>
Date: Tue, 20 May 2025 09:23:09 +0000

From: Taylor Blau <[email-masked]>

After going through the "failed" label, load_bitmap() will return -1,
and its caller (either prepare_bitmap_walk() or prepare_bitmap_git())
will then call free_bitmap_index().

That function would have done:

    struct stored_bitmap *sb;
    kh_foreach_value(b->bitmaps, sb {
      ewah_pool_free(sb->root);
      free(sb);
    });

, but won't since load_bitmap() already called kh_destroy_oid_map() and
NULL'd the "bitmaps" pointer from within its "failed" label.

So I think if you got part of the way through loading bitmap entries and
then failed, you would leak all of the previous entries that you were
able to load successfully.

The solution is to remove the error handling code in load_bitmap(), because
its caller will always call free_bitmap_index() in case of an error.

Signed-off-by: Taylor Blau <[email-masked]>
---
 pack-bitmap.c | 21 ++++-----------------
 1 file changed, 4 insertions(+), 17 deletions(-)

diff --git a/pack-bitmap.c b/pack-bitmap.c
index ac6d62b980c5..fd19c2255163 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -630,41 +630,28 @@ static int load_bitmap(struct repository *r, struct bitmap_index *bitmap_git,
 	bitmap_git->ext_index.positions = kh_init_oid_pos();
 
 	if (load_reverse_index(r, bitmap_git))
-		goto failed;
+		return -1;
 
 	if (!(bitmap_git->commits = read_bitmap_1(bitmap_git)) ||
 		!(bitmap_git->trees = read_bitmap_1(bitmap_git)) ||
 		!(bitmap_git->blobs = read_bitmap_1(bitmap_git)) ||
 		!(bitmap_git->tags = read_bitmap_1(bitmap_git)))
-		goto failed;
+		return -1;
 
 	if (!bitmap_git->table_lookup && load_bitmap_entries_v1(bitmap_git) < 0)
-		goto failed;
+		return -1;
 
 	if (bitmap_git->base) {
 		if (!bitmap_is_midx(bitmap_git))
 			BUG("non-MIDX bitmap has non-NULL base bitmap index");
 		if (load_bitmap(r, bitmap_git->base, 1) < 0)
-			goto failed;
+			return -1;
 	}
 
 	if (!recursing)
 		load_all_type_bitmaps(bitmap_git);
 
 	return 0;
-
-failed:
-	munmap(bitmap_git->map, bitmap_git->map_size);
-	bitmap_git->map = NULL;
-	bitmap_git->map_size = 0;
-
-	kh_destroy_oid_map(bitmap_git->bitmaps);
-	bitmap_git->bitmaps = NULL;
-
-	kh_destroy_oid_pos(bitmap_git->ext_index.positions);
-	bitmap_git->ext_index.positions = NULL;
-
-	return -1;
 }
 
 static int open_pack_bitmap(struct repository *r,
-- 
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