I've learned that the issue is not related to kernel version but caused by environment under which mount is executed.
On my systems (14.04), it fails when executed inside x2go session but manages to operate when connected via physical VT or SSH. May be it's related to apparmor, but how x2go and ssh are different in that perspective? They both spawned as by sshd. Also additional environments like vnc and rdp might be affected. Below is strace of failing attempt. === "ecryptfs-add-passphrase --fnek" works but mount fails: === sudo strace mount -o no_sig_cache,ecryptfs_passthrough=no,ecryptfs_enable_filename_crypto=yes,ecryptfs_cipher=aes,ecryptfs_key_bytes=16,passwd=dummy,ecryptfs_sig=xxxxxxxxxxxxxxxx,ecryptfs_fnek_sig=yyyyyyyyyyyyyyy -t ecryptfs /media/storage/backup/home/.ecryptfs/user/.Private /media/storage/backup/home/user ... stat("/sbin/mount.ecryptfs", {st_mode=S_IFREG|0755, st_size=25880, ...}) = 0 clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7fb366a0bb50) = 11423 wait4(-1, Unable to link the KEY_SPEC_USER_KEYRING into the KEY_SPEC_SESSION_KEYRING; there is something wrong with your kernel keyring. Did you build key retention support into your kernel? [{WIFEXITED(s) && WEXITSTATUS(s) == 251}], 0, NULL) = 11423 --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=11423, si_status=251, si_utime=0, si_stime=1} --- exit_group(251) = ? +++ exited with 251 +++ === ** Changed in: linux (Ubuntu) Status: Incomplete => Opinion ** Also affects: apparmor Importance: Undecided Status: New -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1377924 Title: ecryptfs fails to mount (Unable to link the KEY_SPEC_USER_KEYRING into the KEY_SPEC_SESSION_KEYRING) Status in “apparmor” package in Ubuntu: New Status in “linux” package in Ubuntu: Opinion Status in “openssh” package in Ubuntu: New Bug description: This is a reincarnation of Bug #1234412. Looks like issue is not related to specific kernel versions. Currently I am observing two Trusty (14.04) machines, with very close configuration, running same kernel: 3.13.0-36-generic #63-Ubuntu SMP Wed Sep 3 21:30:07 UTC 2014 x86_64. One is able to mount without the problem but the other is refusing: $ mount -t ecryptfs sec sec Unable to link the KEY_SPEC_USER_KEYRING into the KEY_SPEC_SESSION_KEYRING; there is something wrong with your kernel keyring. Did you build key retention support into your kernel? To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/apparmor/+bug/1377924/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp