[PATCH] security: keys: Use kvfree_sensitive in a few places

[Alex Dewar]

On Fri, Sep 11, 2020 at 05:00:09PM +0100, Alex Dewar wrote:
> On Fri, Sep 11, 2020 at 08:04:24AM -0700, James Bottomley wrote:
> > On Fri, 2020-09-11 at 12:44 +0100, Alex Dewar wrote:
> > > In big_key.c, there are a few places where memzero_explicit + kvfree
> > > is used. It is better to use kvfree_sensitive instead, which is more
> > > readable and also prevents the compiler from eliding the call to
> > > memzero_explicit. Fix this.
> > 
> > That last bit is untrue: the compiler can't elide memzero_explicit ...
> > that's why it has the explicit suffix.
> > 
> > The original problem was a lot of people do memset(.., 0, ..); kfree()
> > which the compiler can elide if it understands the memory is going out
> > of scope.  Or the even more problematic memset(..., 0, ...) on a stack
> > variable before it goes out of scope.
> > 
> > We can argue about readability but there's no secret leak here.
> 
> Ahh, my mistake. Thanks for the explanation.
> 
> I'll send a v2 with an updated commit message. I think it would still
> make sense to use kfree_sensitive here as on next-20200911 this is the
> last use of kzfree in the tree and it would be nice to excise it
> altogether.

Ignore this! I thought we were talking about a different patch :-/

I'll send a respin with a better commit message anyways.

Cheers :-)

> 
> Best,
> Alex
> 
> > 
> > James
> >