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

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Date:   Thu, 18 Apr 2019 11:16:42 -0400
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Paul Moore <paul@...l-moore.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 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.

> > 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

- RGB

--
Richard Guy Briggs <rgb@...hat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635