lkml.org 
[lkml]   [2016]   [Nov]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: vmalloced stacks and scatterwalk_map_and_copy()
On Thu, Nov 03, 2016 at 01:30:49PM -0700, Andy Lutomirski wrote:
>
> Also, Herbert, it seems like the considerable majority of the crypto
> code is acting on kernel virtual memory addresses and does software
> processing. Would it perhaps make sense to add a kvec-based or
> iov_iter-based interface to the crypto code? I bet it would be quite
> a bit faster and it would make crypto on stack buffers work directly.

I'd like to hear Herbert's opinion on this too, but as I understand it, if a
symmetric cipher API operating on virtual addresses was added, similar to the
existing "shash" API it would only allow software processing. Whereas with the
current API you can request a transform and use it the same way regardless of
whether the crypto framework has chosen a software or hardware implementation,
or a combination thereof. If this wasn't a concern then I expect using virtual
addresses would indeed simplify things a lot, at least for users not already
working with physical memory (struct page).

Either way, in the near term it looks like 4.9 will be released with the new
behavior that encryption/decryption is not supported on stack buffers.
Separately from the scatterwalk_map_and_copy() issue, today I've found two
places in the filesystem-level encryption code that do encryption on stack
buffers and therefore hit the 'BUG_ON(!virt_addr_valid(buf));' in sg_set_buf().
I will be sending patches to fix these, but I suspect there may be more crypto
API users elsewhere that have this same problem.

Eric

\
 
 \ /
  Last update: 2016-11-03 22:12    [W:0.153 / U:0.232 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site