[PATCH v2 2/2] KEYS: Avoid false positive ENOMEM error on key read

[David Howells]

Waiman Long <longman at redhat.com> wrote:

> That is not as simple as I thought. First of that, there is not an
> equivalent kzvfree() helper to clear the buffer first before clearing.
> Of course, I can do that manually.

Yeah, the actual substance of vfree() may get deferred.  It may be worth
adding a kvzfree() that switches between kzfree() and memset(),vfree().

> With patch 2, the allocated buffer length will be max(1024, keylen). The
> security code uses kmalloc() for allocation. If we use kvalloc() here,
> perhaps we should also use that for allocation that can be potentially
> large like that in big_key. What do you think?

Not for big_key: if it's larger than BIG_KEY_FILE_THRESHOLD (~1KiB) it gets
written encrypted into shmem so that it can be swapped out to disk when not in
use.

However, other cases, sure - just be aware that on a 32-bit system,
vmalloc/vmap space is a strictly limited resource.

David