Re: [PATCH v2] keys/encrypted: Fix two crypto-on-the-stack bugs

[David Howells]

Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:

> > -       sg_set_buf(&sg_out[1], pad, sizeof pad);
> > +       sg_set_buf(&sg_out[1], empty_zero_page, 16);
> 
> My fix here is obviously bogus (I meant to use ZERO_PAGE(0)), but what
> exactly is the code trying to do?  The old code makes no sense.  It's
> setting the *output* buffer to zeroed padding.

Padding goes into the encrypt function and is going to come out of the decrypt
function.  Possibly derived_key_decrypt() should be checking that the padding
that comes out is actually a bunch of zeros.  Maybe we don't actually need to
get the padding out, but I'm not sure whether the crypto layer will
malfunction if we don't give it a buffer for the padding.

David