Hi Christoph, On Tue, Jun 13, 2017 at 11:52:10PM -0700, Christoph Hellwig wrote: > On Tue, Jun 13, 2017 at 04:47:53PM -0700, Eric Biggers wrote: > > From: Eric Biggers <ebiggers@xxxxxxxxxx> > > > > Currently, filesystems allow truncate(2) on an encrypted file without > > the encryption key. However, it's impossible to correctly handle the > > case where the size being truncated to is not a multiple of the > > filesystem block size, because that would require decrypting the final > > block, zeroing the part beyond i_size, then encrypting the block. > > > > As other modifications to encrypted file contents are prohibited without > > the key, just prohibit truncate(2) as well, making it fail with ENOKEY. > > What about hole punches? What about fallocate which just adds zeroes > but still changes the content. What about insert or collapse range? None of those are allowed because fallocate() requires a file descriptor, and open() fails with ENOKEY if the encryption key is not available. truncate() is different because it takes a path, not a file descriptor. Eric
