encryption on /home/$USER now silently truncates large files

[Marc Nozell]

When I installed Ubuntu 13.04 had my /home/marc encrypted and was able to store large (~40G) files there.

Since upgrading to 13.10 it now *silently* truncates large files to 4G!

Below is a slighly edited session where a 1G file is created correctly, but a 6G file only has 4G written and no errors are given. Notice dd thinks it wrote 6.4G, but ls & df shows only 4G actually was.

This silent failure caused a 41G VM backing file to be truncated to 4G!

marc@hermes:~$ lsb_release -rd
Description: Ubuntu 13.10
Release: 13.10

marc@hermes:~$ df -h
Filesystem Size Used Avail Use% Mounted on
...
/dev/sda7 360G 254G 88G 75% /home
/home/marc/.Private 360G 254G 88G 75% /home/marc

marc@hermes:~$ sudo time dd if=/dev/zero of=/home/marc/1.txt bs=1G count=1
1+0 records in
1+0 records out
1073741824 bytes (1.1 GB) copied, 27.2168 s, 39.5 MB/s
0.00user 4.27system 0:27.28elapsed 15%CPU (0avgtext+0avgdata 1049428maxresident)k
8inputs+2097880outputs (0major+262414minor)pagefaults 0swaps

marc@hermes:~$ ls -ls /home/marc/1.txt
1048588 -rw-r--r-- 1 root root 1073741824 Oct 25 11:33 /home/marc/1.txt

marc@hermes:~$ df -h
Filesystem Size Used Avail Use% Mounted on
...
/dev/sda7 360G 255G 87G 75% /home
/home/marc/.Private 360G 255G 87G 75% /home/marc

marc@hermes:~$ sudo time dd if=/dev/zero of=/home/marc/6.txt bs=1G count=6
6+0 records in
6+0 records out
6442450944 bytes (6.4 GB) copied, 188.545 s, 34.2 MB/s
0.00user 23.34system 3:08.66elapsed 12%CPU (0avgtext+0avgdata 1049428maxresident)k
56inputs+12589088outputs (1major+262412minor)pagefaults 0swaps

marc@hermes:~$ ls -ls /home/marc/6.txt
4194308 -rw-r--r-- 1 root root 6442450944 Oct 25 11:37 /home/marc/6.txt

marc@hermes:~$ df -h
Filesystem Size Used Avail Use% Mounted on
...
/dev/sda7 360G 259G 83G 76% /home
/home/marc/.Private 360G 259G 83G 76% /home/marc

[Sami Jaktholm (sjakthol)]

This sounds a lot like bug 1243636. Are you using 32 bit Ubuntu? You can check that next to "OS type" label from Details panel of System Settings.

[Marc Nozell (marc-nozell)]

Yes the OS type is 32-bit.

And agreed it does sound like https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1243636

[Sami Jaktholm (sjakthol)]

I Marked this as a duplicate of bug 1243636. If you still encounter issues after the fix is released, please report a new bug. Thanks for reporting this one!