linux-kernel - Re: [PATCH ghak111 V1] audit: deliver siginfo regarless of syscall

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Date:   Thu, 18 Apr 2019 11:37:00 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux-Audit Mailing List <linux-audit@...hat.com>,
        sgrubb@...hat.com, omosnace@...hat.com,
        Eric Paris <eparis@...isplace.org>, ebiederm@...ssion.com,
        oleg@...hat.com
Subject: Re: [PATCH ghak111 V1] audit: deliver siginfo regarless of syscall

On Thu, Apr 18, 2019 at 11:16 AM Richard Guy Briggs <rgb@...hat.com> wrote:
> On 2019-04-18 10:59, Paul Moore wrote:
> > On Mon, Apr 8, 2019 at 11:53 PM Richard Guy Briggs <rgb@...hat.com> wrote:
> > > When a process signals the audit daemon (shutdown, rotate, resume,
> > > reconfig) but syscall auditing is not enabled, we still want to know the
> > > identity of the process sending the signal to the audit daemon.
> > >
> > > Move audit_signal_info() out of syscall auditing to general auditing but
> > > create a new function audit_signal_info_syscall() to take care of the
> > > syscall dependent parts for when syscall auditing is enabled.
> > >
> > > Please see the github kernel audit issue
> > > https://github.com/linux-audit/audit-kernel/issues/111
> > >
> > > Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> > > ---
> > >  include/linux/audit.h |  6 ++++++
> > >  kernel/audit.c        | 27 +++++++++++++++++++++++++++
> > >  kernel/audit.h        |  4 ++--
> > >  kernel/auditsc.c      | 19 +++----------------
> > >  kernel/signal.c       |  2 +-
> > >  5 files changed, 39 insertions(+), 19 deletions(-)
> >
> > ...
> >
> > > diff --git a/include/linux/audit.h b/include/linux/audit.h
> > > index 1e69d9fe16da..4a22fc3f824f 100644
> > > --- a/include/linux/audit.h
> > > +++ b/include/linux/audit.h
> > > @@ -226,6 +229,9 @@ static inline unsigned int audit_get_sessionid(struct task_struct *tsk)
> > >  }
> > >
> > >  #define audit_enabled AUDIT_OFF
> > > +
> > > +#define audit_signal_info(s, t) AUDIT_OFF
> > > +
> >
> > Should this be AUDIT_DISABLED to preserve the current value/behavior?
> > Technically they should both have a value of zero right now, but since
> > the AUDIT_DISABLED value isn't explicit it seems safer to go with
> > AUDIT_DISABLED.
>
> I did that first, but that symbol was not available when one or both of
> CONFIG_AUDITSYSCALL or CONFIG_AUDIT was off, so I had to change it to
> AUDIT_OFF.  I followed the logic to confirm that is what was intended by
> the original code.
>
> When auidit is off, we want to just return zero so it gets skipped
> rather than throwing an error.

I understand the desire to return zero in that case, I'm not arguing
against that, I'm just not really in love with how these are defined
when CONFIG_AUDIT isn't.  Part of it is the AUDIT_DISABLED/AUDIT_OFF
change, part of it is the function being defined as a cpp macro
instead of a dummy function (this of course predates your change).
Based on other comments in this thread it looks like you're looking
into a few things and will likely be respinning this patch, since that
is the case, I would prefer if you changed this to just using simply
"0" as opposed to AUDIT_OFF.

If you really want to make me happy about this patch, you would also
change this to a dummy function instead of a cpp macro.  This is a
style nit, and isn't strictly necessary, but I would appreciate it :)

> > > diff --git a/kernel/audit.h b/kernel/audit.h
> > > index 958d5b8fc1b3..18a8ae812e9f 100644
> > > --- a/kernel/audit.h
> > > +++ b/kernel/audit.h
> > > @@ -299,7 +299,7 @@ extern bool audit_tree_match(struct audit_chunk *chunk,
> > >  extern void audit_put_tree(struct audit_tree *tree);
> > >  extern void audit_kill_trees(struct audit_context *context);
> > >
> > > -extern int audit_signal_info(int sig, struct task_struct *t);
> > > +extern int audit_signal_info_syscall(struct task_struct *t);
> > >  extern void audit_filter_inodes(struct task_struct *tsk,
> > >                                 struct audit_context *ctx);
> > >  extern struct list_head *audit_killed_trees(void);
> > > @@ -330,7 +330,7 @@ extern void audit_filter_inodes(struct task_struct *tsk,
> > >  #define audit_tree_path(rule) ""       /* never called */
> > >  #define audit_kill_trees(context) BUG()
> > >
> > > -#define audit_signal_info(s, t) AUDIT_DISABLED
> > > +#define audit_signal_info_syscall(t) AUDIT_OFF
> >
> > Similar as above.

-- 
paul moore
www.paul-moore.com