[PATCH 1/6] index-pack, unpack-objects: use size_t for object size

From: Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>
Date: Apr 28, 2026, 16:26 UTC
Message-ID: <dc660106ea8511e6adc44d2b70e9a4ae8b18090e.1777393580.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.2102.git.1777393580.gitgitgadget@gmail.com>

From: Johannes Schindelin <johannes.schindelin@gmx.de>

When unpacking objects from a packfile, the object size is decoded from a variable-length encoding. On platforms where unsigned long is 32-bit (such as Windows, even in 64-bit builds), the shift operation overflows when decoding sizes larger than 4GB. The result is a truncated size value, causing the unpacked object to be corrupted or rejected.

Fix this by changing the size variable to size_t, which is 64-bit on 64-bit platforms, and ensuring the shift arithmetic occurs in 64-bit space.

This was originally authored by LordKiRon <https://github.com/LordKiRon>, who preferred not to reveal their real name and therefore agreed that I take over authorship.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 builtin/index-pack.c     | 9 +++++----
 builtin/unpack-objects.c | 5 +++--
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index ca7784dc2c..cc660582e9 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -37,7 +37,7 @@ static const char index_pack_usage[] =
 
 struct object_entry {
 	struct pack_idx_entry idx;
-	unsigned long size;
+	size_t size;
 	unsigned char hdr_size;
 	signed char type;
 	signed char real_type;
@@ -469,7 +469,7 @@ static int is_delta_type(enum object_type type)
 	return (type == OBJ_REF_DELTA || type == OBJ_OFS_DELTA);
 }
 
-static void *unpack_entry_data(off_t offset, unsigned long size,
+static void *unpack_entry_data(off_t offset, size_t size,
 			       enum object_type type, struct object_id *oid)
 {
 	static char fixed_buf[8192];
@@ -524,7 +524,8 @@ static void *unpack_raw_entry(struct object_entry *obj,
 			      struct object_id *oid)
 {
 	unsigned char *p;
-	unsigned long size, c;
+	size_t size;
+	unsigned long c;
 	off_t base_offset;
 	unsigned shift;
 	void *data;
@@ -542,7 +543,7 @@ static void *unpack_raw_entry(struct object_entry *obj,
 		p = fill(1);
 		c = *p;
 		use(1);
-		size += (c & 0x7f) << shift;
+		size += ((size_t)c & 0x7f) << shift;
 		shift += 7;
 	}
 	obj->size = size;
diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
index e01cf6e360..59a36c2481 100644
--- a/builtin/unpack-objects.c
+++ b/builtin/unpack-objects.c
@@ -533,7 +533,8 @@ static void unpack_one(unsigned nr)
 {
 	unsigned shift;
 	unsigned char *pack;
-	unsigned long size, c;
+	size_t size;
+	unsigned long c;
 	enum object_type type;
 
 	obj_list[nr].offset = consumed_bytes;
@@ -548,7 +549,7 @@ static void unpack_one(unsigned nr)
 		pack = fill(1);
 		c = *pack;
 		use(1);
-		size += (c & 0x7f) << shift;
+		size += ((size_t)c & 0x7f) << shift;
 		shift += 7;
 	}

-- 
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