Re: [PATCH v3 00/13] fscrypt: improve file creation flow

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2020-09-21 at 15:35 -0700, Eric Biggers wrote:
> On Wed, Sep 16, 2020 at 09:11:23PM -0700, Eric Biggers wrote:
> > Hello,
> > 
> > This series reworks the implementation of creating new encrypted files
> > by introducing new helper functions that allow filesystems to set up the
> > inodes' keys earlier, prior to taking too many filesystem locks.
> > 
> > This fixes deadlocks that are possible during memory reclaim because
> > fscrypt_get_encryption_info() isn't GFP_NOFS-safe, yet it's called
> > during an ext4 transaction or under f2fs_lock_op().  It also fixes a
> > similar deadlock where f2fs can try to recursively lock a page when the
> > test_dummy_encryption mount option is in use.
> > 
> > It also solves an ordering problem that the ceph support for fscrypt
> > will have.  For more details about this ordering problem, see the
> > discussion on Jeff Layton's RFC patchsets for ceph fscrypt support
> > (v1: https://lkml.kernel.org/linux-fscrypt/20200821182813.52570-1-jlayton@kernel.org/T/#u
> >  v2: https://lkml.kernel.org/linux-fscrypt/20200904160537.76663-1-jlayton@kernel.org/T/#u
> >  v3: https://lkml.kernel.org/linux-fscrypt/20200914191707.380444-1-jlayton@kernel.org/T/#u)
> > Note that v3 of the ceph patchset is based on v2 of this patchset.
> > 
> > Patch 1 adds the above-mentioned new helper functions.  Patches 2-5
> > convert ext4, f2fs, and ubifs to use them, and patches 6-9 clean up a
> > few things afterwards.
> > 
> > Finally, patches 10-13 change the implementation of
> > test_dummy_encryption to no longer set up an encryption key for
> > unencrypted directories, which was confusing and was causing problems.
> > 
> > This patchset applies to the master branch of
> > https://git.kernel.org/pub/scm/fs/fscrypt/fscrypt.git.
> > It can also be retrieved from tag "fscrypt-file-creation-v3" of
> > https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git.
> > 
> > I'm looking to apply this for 5.10; reviews are greatly appreciated!
> > 
> > Changed v2 => v3:
> >   - Added patch that changes fscrypt_set_test_dummy_encryption() to take
> >     a 'const char *'.  (Needed by ceph.)
> >   - Fixed bug where fscrypt_prepare_new_inode() succeeded even if the
> >     new inode's key couldn't be set up.
> >   - Fixed bug where fscrypt_prepare_new_inode() wouldn't derive the
> >     dirhash key for new casefolded directories.
> >   - Made warning messages account for i_ino possibly being 0 now.
> > 
> > Changed v1 => v2:
> >   - Added mention of another deadlock this fixes.
> >   - Added patches to improve the test_dummy_encryption implementation.
> >   - Dropped an ext4 cleanup patch that can be done separately later.
> >   - Lots of small cleanups, and a couple small fixes.
> > 
> > Eric Biggers (13):
> >   fscrypt: add fscrypt_prepare_new_inode() and fscrypt_set_context()
> >   ext4: factor out ext4_xattr_credits_for_new_inode()
> >   ext4: use fscrypt_prepare_new_inode() and fscrypt_set_context()
> >   f2fs: use fscrypt_prepare_new_inode() and fscrypt_set_context()
> >   ubifs: use fscrypt_prepare_new_inode() and fscrypt_set_context()
> >   fscrypt: adjust logging for in-creation inodes
> >   fscrypt: remove fscrypt_inherit_context()
> >   fscrypt: require that fscrypt_encrypt_symlink() already has key
> >   fscrypt: stop pretending that key setup is nofs-safe
> >   fscrypt: make "#define fscrypt_policy" user-only
> >   fscrypt: move fscrypt_prepare_symlink() out-of-line
> >   fscrypt: handle test_dummy_encryption in more logical way
> >   fscrypt: make fscrypt_set_test_dummy_encryption() take a 'const char
> >     *'
> 
> All applied to fscrypt.git#master for 5.10.
> 
> I'd still really appreciate more reviews and acks, though.
> 

You can add this to all of the fscrypt: patches. I've tested this under
the ceph patchset and it seems to do the right thing:

Acked-by: Jeff Layton <jlayton@kernel.org>