Re: [PATCH v2] kernel: audit.c: Add __rcu notation to RCU pointer

[Ondrej Mosnacek]

On Wed, Apr 15, 2020 at 6:15 PM Richard Guy Briggs <rgb@xxxxxxxxxx> wrote:
> On 2020-04-15 12:06, Paul Moore wrote:
> > On Wed, Apr 15, 2020 at 11:34 AM Richard Guy Briggs <rgb@xxxxxxxxxx> wrote:
> > > On 2019-11-29 21:07, Joel Fernandes wrote:
> > > > On Thu, Nov 28, 2019 at 09:02:03PM +0530, Amol Grover wrote:
> > > > > add __rcu notation to RCU protected global pointer auditd_conn
> > > >
> > > > Again, please use proper punctuation and captilization. This is unacceptable.
> > > > Please put more effort into changelog.
> > > >
> > > > Otherwise the patch diff itself looks good to me, with the above nit
> > > > corrected, you could add my tag to the next revision:
> > > >
> > > > Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
> > > >
> > > > thanks,
> > > >
> > > >  - Joel
> > > >
> > > > >
> > > > > Fixes multiple instances of sparse error:
> > > > > error: incompatible types in comparison expression
> > > > > (different address spaces)
> > >
> > > Amol or Joel: Is there a reproducer recipe for this?
> >
> > The commit which was merged has a slightly better description which may help.
>
> I've already seen this.  Perhaps I should have replied to this message
> instead to make that evident.  What really needed was Amol's original
> message sent to this list, but it was Joel who included this list in his
> reply (all 3 versions).
>
> I'm looking for the specific setup and commands that produced this error.

You can run make with "C=1", which will run sparse on all files that
are rebuilt during that make run. For example, if I fully build the
kernel and then revert commit
cb5172d96d16df72db8b55146b0ec00bfd97f079, I get:

$ make [...] C=1
[...]
  CHECK   [...]/kernel/audit.c
[...]/kernel/audit.c:218:14: error: incompatible types in comparison
expression (different address spaces):
[...]/kernel/audit.c:218:14:    struct auditd_connection [noderef] <asn:4> *
[...]/kernel/audit.c:218:14:    struct auditd_connection *
(...and a lot more errors like this + 2 different warnings)

And when I un-revert it again, I get only the 2 warnings.

-- 
Ondrej Mosnacek <omosnace at redhat dot com>
Software Engineer, Security Technologies
Red Hat, Inc.