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? Thanks! - Eric
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