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Re: [PATCH 26/26] ubifs: Raise write version to 5

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On Fri, Oct 21, 2016 at 11:19:31AM -0700, Eric Biggers wrote:
> 
> I don't think it's reasonable to require require changes to filesystems whenever
> someone introduces a new encryption mode --- contents, filenames, or both.
> Filesystems need to be able to handle unsupported encryption modes in some way
> that makes sense.  Currently, when it sees an unsupported encryption mode
> fscrypto will behave as if the encryption key is not available and will also
> print a one-time warning to the kernel log.  This happens when a file is
> accessed, not when the filesystem is mounted.  As far as I can tell, ext4, f2fs,
> and ubifs would all behave this way because this code is shared.  I think this
> is probably the most realistic behavior.

I tend to agree, but file systems may choose some alternate approach
if they want to "fail fast" (e.g., at mount time).  I wouldn't want to
do that for ext4, but if ubifs (or some other file system) wants do
something more draconian, they can be afraid to do that.  Failing
that, some kind of one-time warning makes sense.

What I would like to do though is to is to have a callback so that
code in fs/crypto can call a file system specific notification
routine.  e.g., for ext4, we would probably want to be able to call
ext4_warning() and ext4_error() from fs/crypto, and other file systems
might want to have a different set of notification routines.

This way we can print a message like

kernel: EXT4-fs warning (device sdb1): fscrypto_xxx: foo bar baz

and if we later on have a way of sending file system specific warnings
or errors through some kind of IPC mechanism, such as netlink or some
future kdbus scheme, we can send the warning and error messages out
the same way we send other filesystem specific error messages.

	      	      	     	       	      - Ted

P.S.  BTW, we actually _do_ have something hacked together inside the
Google production kernel which pipes ext4_error() messages to a
netlink socket, so that monitoring systems don't have scrape dmesg or
/var/log/messages.

If anyone inside or outside google is interested in that
functionality, I can make the code available.  There's nothing
sensitive or Google specific in it; it's just that unfortunately,
getting that code cleaned up and upstreamed has just never made it
"above the fold" on the priority list, the engineer who originally
implemented it is no longer on the team --- and I never had the time
to cleanup work to get the code to upstream quality myself.

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[PATCH 00/26] UBIFS File Encryption Richard Weinberger <richard@nod.at> - 2016-10-21 14:50 +0200
  [PATCH 26/26] ubifs: Raise write version to 5 Richard Weinberger <richard@nod.at> - 2016-10-21 14:50 +0200
    Re: [PATCH 26/26] ubifs: Raise write version to 5 Michael Halcrow <mhalcrow@google.com> - 2016-10-21 19:40 +0200
      Re: [PATCH 26/26] ubifs: Raise write version to 5 Theodore Ts'o <tytso@mit.edu> - 2016-10-21 19:50 +0200
        Re: [PATCH 26/26] ubifs: Raise write version to 5 Eric Biggers <ebiggers@google.com> - 2016-10-21 20:20 +0200
          Re: [PATCH 26/26] ubifs: Raise write version to 5 Theodore Ts'o <tytso@mit.edu> - 2016-10-22 00:40 +0200
        Re: [PATCH 26/26] ubifs: Raise write version to 5 Richard Weinberger <richard@nod.at> - 2016-10-24 09:10 +0200
  [PATCH 05/26] ubifs: Define UBIFS crypto context xattr Richard Weinberger <richard@nod.at> - 2016-10-21 14:50 +0200
  [PATCH 10/26] ubifs: Enforce crypto policy in ->link and ->rename Richard Weinberger <richard@nod.at> - 2016-10-21 14:50 +0200
  [PATCH 15/26] ubifs: Implement encrypt/decrypt for all IO Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
    Re: [PATCH 15/26] ubifs: Implement encrypt/decrypt for all IO Michael Halcrow <mhalcrow@google.com> - 2016-10-21 19:20 +0200
      Re: [PATCH 15/26] ubifs: Implement encrypt/decrypt for all IO Richard Weinberger <richard@nod.at> - 2016-10-21 19:30 +0200
        Re: [PATCH 15/26] ubifs: Implement encrypt/decrypt for all IO Michael Halcrow <mhalcrow@google.com> - 2016-10-21 20:00 +0200
          Re: [PATCH 15/26] ubifs: Implement encrypt/decrypt for all IO Richard Weinberger <richard@nod.at> - 2016-10-21 20:30 +0200
    Re: [PATCH 15/26] ubifs: Implement encrypt/decrypt for all IO Eric Biggers <ebiggers@google.com> - 2016-10-21 20:30 +0200
      Re: [PATCH 15/26] ubifs: Implement encrypt/decrypt for all IO Richard Weinberger <richard@nod.at> - 2016-10-24 09:10 +0200
  [PATCH 07/26] ubifs: Massage ubifs_listxattr() for encryption context Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 13/26] ubifs: Enforce crypto policy in mmap Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 11/26] ubifs: Preload crypto context in ->lookup() Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 21/26] ubifs: Rename tnc_read_node_nm Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 12/26] ubifs: Massage assert in ubifs_xattr_set() wrt. fscrypto Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 02/26] fscrypto: Constify struct inode pointer Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
    Re: [PATCH 02/26] fscrypto: Constify struct inode pointer Theodore Ts'o <tytso@mit.edu> - 2016-10-21 17:00 +0200
      Re: [PATCH 02/26] fscrypto: Constify struct inode pointer Richard Weinberger <richard@nod.at> - 2016-10-21 17:20 +0200
  [PATCH 22/26] ubifs: Add full hash lookup support Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 24/26] ubifs: Implement UBIFS_FLG_DOUBLE_HASH Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 25/26] ubifs: Implement UBIFS_FLG_ENCRYPTION Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
    Re: [PATCH 25/26] ubifs: Implement UBIFS_FLG_ENCRYPTION Eric Biggers <ebiggers@google.com> - 2016-10-21 20:40 +0200
      Re: [PATCH 25/26] ubifs: Implement UBIFS_FLG_ENCRYPTION Richard Weinberger <richard@nod.at> - 2016-10-24 09:00 +0200
        Re: [PATCH 25/26] ubifs: Implement UBIFS_FLG_ENCRYPTION Theodore Ts'o <tytso@mit.edu> - 2016-10-24 15:50 +0200
  [PATCH 17/26] ubifs: Make r5 hash binary string aware Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 20/26] ubifs: Add support for encrypted symlinks Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
    Re: [PATCH 20/26] ubifs: Add support for encrypted symlinks Eric Biggers <ebiggers@google.com> - 2016-10-21 20:50 +0200
      Re: [PATCH 20/26] ubifs: Add support for encrypted symlinks Richard Weinberger <richard@nod.at> - 2016-10-24 09:00 +0200
  [PATCH 23/26] ubifs: Use a random number for cookies Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 08/26] ubifs: Implement directory open operation Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 14/26] ubifs: Introduce new data node field, compr_size Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 16/26] ubifs: Relax checks in ubifs_validate_entry() Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 18/26] ubifs: Constify struct inode pointer in ubifs_crypt_is_encrypted() Richard Weinberger <richard@nod.at> - 2016-10-21 15:00 +0200
  [PATCH 06/26] ubifs: Add skeleton for fscrypto Richard Weinberger <richard@nod.at> - 2016-10-21 15:10 +0200
  Re: [PATCH 01/26] fscrypto: Add buffer operations Christoph Hellwig <hch@infradead.org> - 2016-10-21 15:10 +0200
    Re: [PATCH 01/26] fscrypto: Add buffer operations Richard Weinberger <richard@nod.at> - 2016-10-21 15:20 +0200
      Re: [PATCH 01/26] fscrypto: Add buffer operations Christoph Hellwig <hch@infradead.org> - 2016-10-21 15:30 +0200
        Re: [PATCH 01/26] fscrypto: Add buffer operations Theodore Ts'o <tytso@mit.edu> - 2016-10-21 17:20 +0200
        Re: [PATCH 01/26] fscrypto: Add buffer operations Richard Weinberger <richard@nod.at> - 2016-10-24 09:10 +0200
  [PATCH 09/26] ubifs: Implement file open operation Richard Weinberger <richard@nod.at> - 2016-10-21 15:10 +0200
  [PATCH 03/26] ubifs: Export ubifs_check_dir_empty() Richard Weinberger <richard@nod.at> - 2016-10-21 15:10 +0200
  [PATCH 04/26] ubifs: Export xattr get and set functions Richard Weinberger <richard@nod.at> - 2016-10-21 15:10 +0200
  [PATCH 01/26] fscrypto: Add buffer operations Richard Weinberger <richard@nod.at> - 2016-10-21 15:10 +0200

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