ecryptfs mounting failure from kernel 4.7 onwards

Question

Up until kernel 4.6 I was able to mount ecryptfs mounts which had top-level directory plain but lower directories encrypted.

From kernel 4.7 onwards I cannot do that anymore.

Encrypted home is at /.private/backup and mount point is at /mountpoint.

Mounting is done from .private not from .private/backup as shown below:

$> mount -t ecryptfs /.private /mountpoint

$> ls /mountpoint/backup

ls: cannot access /mountpoint/backup: No such file or directory

?????????? ? ? ? ? ? backup

If I mount

$> mount -t ecryptfs /.private/backup /mountpoint

then everything is OK.

I am using the following options rw,noauto,user,no_sig_cache,ecryptfs_passthrough=n,ecryptfs_sig=xxxxxx,ecryptfs_cipher=blowfish,ecryptfs_key_bytes=56,ecryptfs_fnek_sig=xxxxxxx,ecryptfs_unlink_sigs,key=passphrase:passphrase_passwd_file=/root/.ecryptfs/passwd.txt

Using ecryptfs_passthrough=y did not seem to make any difference.

What could be the reason?

Answer 1

The ability to look up plaintext and encrypted filenames, under the same eCryptfs mount point, has been disabled with the following commit in 4.7:

https://git.kernel.org/linus/88ae4ab9802eaa8e400e611f85883143d89d6b61

Supporting both forms of filenames in the lower filesystem has proved to be problematic and it was decided that only one or the other should be usable under a given eCryptfs mount point. I'm sorry to hear that your use case was affected by the decision but I don't think that use case can be supported at this time.