[BUG] ecryptfs leaks an inode on lookup failure -> kernel BUG in generic_shutdown_super()

[Farhad Alemi]

Hello,

As part of the kernel research at ASU's SEFCOM
lab, we hit the crash below. Crash reports can be found here:

  https://github.com/farhad-alemi/public_bug_reports/tree/main/128-ecryptfs-i_new-inode-leak-lookup-failure/

  ecryptfs_i_size_read: Error attempting to initialize the lower file
for the dentry with name [victim]; rc = [-26]
  VFS: Busy inodes after unmount of ecryptfs (ecryptfs)
  kernel BUG at fs/super.c:779!
  Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
  Call Trace:
   kill_anon_super+0x3b/0x70
   ecryptfs_kill_block_super+0x44/0xa0
   deactivate_locked_super+0xbc/0x110
   cleanup_mnt+0x437/0x4d0
   task_work_run+0x1d9/0x270
   exit_to_user_mode_loop+0x14e/0x540
   do_syscall_64+0x317/0x510
  Kernel panic - not syncing: Fatal exception

Our reproducer.c is available upon request.

Happy to test a patch if that would help.

Regards,