[PATCH] pack-bitmap: fix memory leak if `load_bitmap_entries_v1` failed

From: Lidong Yan via GitGitGadget <gitgitgadget@gmail.com>
Date: May 12, 2025, 12:22 UTC
Message-ID: <pull.1962.git.git.1747052530271.gitgitgadget@gmail.com>

From: Lidong Yan <502024330056@smail.nju.edu.cn>

In pack-bitmap.c:load_bitmap_entries_v1, the function `read_bitmap_1` allocates a bitmap and reads index data into it. However, if any of the validation checks following the allocation fail, the allocated bitmap is not freed, resulting in a memory leak. To avoid this, the validation checks should be performed before the bitmap is allocated.

Signed-off-by: Lidong Yan <502024330056@smail.nju.edu.cn>
---
    pack-bitmap: fix memory leak if load_bitmap_entries_v1 failed
    
    In pack-bitmap.c:load_bitmap_entries_v1, the function read_bitmap_1
    allocates a bitmap and reads index data into it. However, if any of the
    validation checks following the allocation fail, the allocated bitmap is
    not freed, resulting in a memory leak. To avoid this, the validation
    checks should be performed before the bitmap is allocated.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1962%2Fbrandb97%2Ffix-pack-bitmap-leak-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1962/brandb97/fix-pack-bitmap-leak-v1
Pull-Request: https://github.com/git/git/pull/1962

 pack-bitmap.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pack-bitmap.c b/pack-bitmap.c
index b9f1d866046..ac6d62b980c 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -388,10 +388,6 @@ static int load_bitmap_entries_v1(struct bitmap_index *index)
 			return error(_("corrupt ewah bitmap: commit index %u out of range"),
 				     (unsigned)commit_idx_pos);
 
-		bitmap = read_bitmap_1(index);
-		if (!bitmap)
-			return -1;
-
 		if (xor_offset > MAX_XOR_OFFSET || xor_offset > i)
 			return error(_("corrupted bitmap pack index"));
 
@@ -402,6 +398,10 @@ static int load_bitmap_entries_v1(struct bitmap_index *index)
 				return error(_("invalid XOR offset in bitmap pack index"));
 		}
 
+		bitmap = read_bitmap_1(index);
+		if (!bitmap)
+			return -1;
+
 		recent_bitmaps[i % MAX_XOR_OFFSET] = store_bitmap(
 			index, bitmap, &oid, xor_bitmap, flags);
 	}

base-commit: 6f84262c44a89851c3ae5a6e4c1a9d06b2068d75

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