Re: [PATCH] Use memzero_explicit to clear local buffers

[Giel van Schijndel <me@mortis.eu>]

[-- Attachment #1: Type: text/plain, Size: 1042 bytes --]

On Mon, Jan 05, 2015 at 10:36:37 +1100, Herbert Xu wrote:
> On Sun, Jan 04, 2015 at 11:49:09PM +0100, Giel van Schijndel wrote:
>>
>>> sctx does not point to stack memory so this is bogus.
>>> 
>>> Only stack memory cleared just before it goes out of scope needs
>>> memzero_explicit.
>> 
>> Is that because the compiler can't safely optimize memset(0) away for a
>> variable with greater-than-local scope?
> 
> Exactly.  memzero_explicit is not a marker for sensitive data.
> Its only purpose is to prevent the compiler from optimising away
> zeroing that occurs at the end of a scope.

Question: are you sure the compiler won't optimize the call to memset(0)
way if it's immediately followed by kfree()?

Because one of my changes concerns that situation.

Another actually does change a stack-allocated buffer, I'll split that
one off right away.

-- 
Met vriendelijke groet,
With kind regards,
Giel van Schijndel
--
"When all you have is a hammer, everything starts to look like a nail."
  -- Abraham Maslow

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 181 bytes --]