static void start_packfile(void)
{
	static char tmp_file[PATH_MAX];
	struct packed_git *p;
	int namelen;
	struct pack_header hdr;
	int pack_fd;

	pack_fd = odb_mkstemp(tmp_file, sizeof(tmp_file),
			      "pack/tmp_pack_XXXXXX");
	namelen = strlen(tmp_file) + 2;
	p = xcalloc(1, sizeof(*p) + namelen);
	xsnprintf(p->pack_name, namelen, "%s", tmp_file);
	p->pack_fd = pack_fd;
	p->do_not_close = 1;
	pack_file = sha1fd(pack_fd, p->pack_name);

	hdr.hdr_signature = htonl(PACK_SIGNATURE);
	hdr.hdr_version = htonl(2);
	hdr.hdr_entries = 0;
	sha1write(pack_file, &hdr, sizeof(hdr));

	pack_data = p;
	pack_size = sizeof(hdr);
	object_count = 0;

	REALLOC_ARRAY(all_packs, pack_id + 1);
	all_packs[pack_id] = p;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.