On Wednesday, May 1, 2019 4:38:41 AM IST Eric Biggers wrote:
> On Tue, Apr 30, 2019 at 10:11:35AM -0700, Eric Biggers wrote:
> > On Sun, Apr 28, 2019 at 10:01:18AM +0530, Chandan Rajendra wrote:
> > > For subpage-sized blocks, this commit now encrypts all blocks mapped by
> > > a page range.
> > >
> > > Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxx>
> > > ---
> > > fs/crypto/crypto.c | 37 +++++++++++++++++++++++++------------
> > > 1 file changed, 25 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
> > > index 4f0d832cae71..2d65b431563f 100644
> > > --- a/fs/crypto/crypto.c
> > > +++ b/fs/crypto/crypto.c
> > > @@ -242,18 +242,26 @@ struct page *fscrypt_encrypt_page(const struct inode *inode,
> >
> > Need to update the function comment to clearly explain what this function
> > actually does now.
> >
> > > {
> > > struct fscrypt_ctx *ctx;
> > > struct page *ciphertext_page = page;
> > > + int i, page_nr_blks;
> > > int err;
> > >
> > > BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0);
> > >
> >
> > Make a 'blocksize' variable so you don't have to keep calling i_blocksize().
> >
> > Also, you need to check whether 'len' and 'offs' are filesystem-block-aligned,
> > since the code now assumes it.
> >
> > const unsigned int blocksize = i_blocksize(inode);
> >
> > if (!IS_ALIGNED(len | offs, blocksize))
> > return -EINVAL;
> >
> > However, did you check whether that's always true for ubifs? It looks like it
> > may expect to encrypt a prefix of a block, that is only padded to the next
> > 16-byte boundary.
> >
> > > + page_nr_blks = len >> inode->i_blkbits;
> > > +
> > > if (inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES) {
> > > /* with inplace-encryption we just encrypt the page */
> > > - err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num, page,
> > > - ciphertext_page, len, offs,
> > > - gfp_flags);
> > > - if (err)
> > > - return ERR_PTR(err);
> > > -
> > > + for (i = 0; i < page_nr_blks; i++) {
> > > + err = fscrypt_do_page_crypto(inode, FS_ENCRYPT,
> > > + lblk_num, page,
> > > + ciphertext_page,
> > > + i_blocksize(inode), offs,
> > > + gfp_flags);
> > > + if (err)
> > > + return ERR_PTR(err);
>
> Apparently ubifs does encrypt data shorter than the filesystem block size, so
> this part is wrong.
>
> I suggest we split this into two functions, fscrypt_encrypt_block_inplace() and
> fscrypt_encrypt_blocks(), so that it's conceptually simpler what each function
> does. Currently this works completely differently depending on whether the
> filesystem set FS_CFLG_OWN_PAGES in its fscrypt_operations, which is weird.
>
> I also noticed that using fscrypt_ctx for writes seems to be unnecessary.
> AFAICS, page_private(bounce_page) could point directly to the pagecache page.
> That would simplify things a lot, especially since then fscrypt_ctx could be
> removed entirely after you convert reads to use read_callbacks_ctx.
>
> IMO, these would be worthwhile cleanups for fscrypt by themselves, without
> waiting for the read_callbacks stuff to be finalized. Finalizing the
> read_callbacks stuff will probably require reaching a consensus about how they
> should work with future filesystem features like fsverity and compression.
>
> So to move things forward, I'm considering sending out a series with the above
> cleanups for fscrypt, plus the equivalent of your patches:
>
> "fscrypt_encrypt_page: Loop across all blocks mapped by a page range"
> "fscrypt_zeroout_range: Encrypt all zeroed out blocks of a page"
> "Add decryption support for sub-pagesized blocks" (fs/crypto/ part only)
>
> Then hopefully we can get all that applied for 5.3 so that fs/crypto/ itself is
> ready for blocksize != PAGE_SIZE; and get your changes to ext4_bio_write_page(),
> __ext4_block_zero_page_range(), and ext4_block_write_begin() applied too, so
> that ext4 is partially ready for encryption with blocksize != PAGE_SIZE.
>
> Then only the read_callbacks stuff will remain, to get encryption support into
> fs/mpage.c and fs/buffer.c. Do you think that's a good plan?
Hi Eric,
IMHO, I will continue posting the next version of the current patchset and if
there are no serious reservations from FS maintainers the "read callbacks"
patchset can be merged. In such a scenario, the cleanups being
non-complicated, can be merged later.
--
chandan
