df -h returns wrong line seperate

[JoeyJiao]

$ df -h
Filesystem Size Used Avail Use% Mounted on
udev 126G 0 126G 0% /dev
tmpfs 26G 52M 26G 1% /run
/dev/mapper/ubuntu--vg-root 573G 411G 134G 76% /
tmpfs 126G 220K 126G 1% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 126G 0 126G 0% /sys/fs/cgroup
/dev/sda1 472M 169M 279M 38% /boot
tmpfs 26G 92K 26G 1% /run/user/1000

But the cmd_buff returned from busybox df_main is:
(gdb) p cmd_buff
$3 = "Filesystem", ' ' <repeats 16 times>, "Size Used Available Use% Mounted on\nudev", ' ' <repeats 20 times>, "125.9G 0 125.9G 0% /dev\ntmpfs", ' ' <repeats 20 times>, "25.2G 51.5M 25.1G 0% /run\n/dev/mapper/ubuntu--vg-root\n", ' ' <repeats 24 times>, "572.6G 410.3G 133.2G 75% /\ntmpfs", ' ' <repeats 19 times>, "125.9G 220.0K 125.9G 0% /dev/shm\ntmpfs", ' ' <repeats 21 times>, "5.0M 0 5.0M 0% /run/lock\ntmpfs", ' ' <repeats 19 times>, "125.9G 0 125.9G 0% /sys/fs/cgroup\n/dev/sda1", ' ' <repeats 15 times>, "471.6M 168.8M 278.4M 38% /boot\ntmpfs", ' ' <repeats 20 times>, "25.2G 92.0K 25.2G 0% /run/user/1000\n/dev/mapper/ubuntu--vg-root\n", ' ' <repeats 24 times>, "572.6G 410.3G 133.2G 75% /var/lib/docker/aufs\n", '\000' <repeats 7476 times>

There is unexpected \n after /dev/mapper/ubuntu--vg-root\n which results lepv parse error.