linux-kernel - Re: [PATCH v1 1/2] audit: record fanotify event regardless of presence of rules

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Message-ID: <Z8tGyiUzX6p+2vpp@madcap2.tricolour.ca>
Date: Fri, 7 Mar 2025 14:19:38 -0500
From: Richard Guy Briggs <rgb@...hat.com>
To: Jan Kara <jack@...e.cz>
Cc: Linux-Audit Mailing List <linux-audit@...ts.linux-audit.osci.io>,
	LKML <linux-kernel@...r.kernel.org>, linux-fsdevel@...r.kernel.org,
	Linux Kernel Audit Mailing List <audit@...r.kernel.org>,
	Paul Moore <paul@...l-moore.com>,
	Eric Paris <eparis@...isplace.org>, Steve Grubb <sgrubb@...hat.com>,
	Amir Goldstein <amir73il@...il.com>
Subject: Re: [PATCH v1 1/2] audit: record fanotify event regardless of
 presence of rules

On 2025-03-07 15:52, Jan Kara wrote:
> On Thu 06-03-25 20:12:23, Richard Guy Briggs wrote:
> > On 2025-03-06 16:06, Jan Kara wrote:
> > > On Wed 05-03-25 16:33:19, Richard Guy Briggs wrote:
> > > > When no audit rules are in place, fanotify event results are
> > > > unconditionally dropped due to an explicit check for the existence of
> > > > any audit rules.  Given this is a report from another security
> > > > sub-system, allow it to be recorded regardless of the existence of any
> > > > audit rules.
> > > > 
> > > > To test, install and run the fapolicyd daemon with default config.  Then
> > > > as an unprivileged user, create and run a very simple binary that should
> > > > be denied.  Then check for an event with
> > > > 	ausearch -m FANOTIFY -ts recent
> > > > 
> > > > Link: https://issues.redhat.com/browse/RHEL-1367
> > > > Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> > > 
> > > I don't know enough about security modules to tell whether this is what
> > > admins want or not so that's up to you but:
> > > 
> > > > -static inline void audit_fanotify(u32 response, struct fanotify_response_info_audit_rule *friar)
> > > > -{
> > > > -	if (!audit_dummy_context())
> > > > -		__audit_fanotify(response, friar);
> > > > -}
> > > > -
> > > 
> > > I think this is going to break compilation with !CONFIG_AUDITSYSCALL &&
> > > CONFIG_FANOTIFY?
> > 
> > Why would that break it?  The part of the patch you (prematurely)
> > deleted takes care of that.
> 
> So I'm failing to see how it takes care of that when with
> !CONFIG_AUDITSYSCALL kernel/auditsc.c does not get compiled into the kernel.
> So what does provide the implementation of audit_fanotify() in that case?
> I think you need to provide empty audit_fanotify() inline wrapper for that
> case...

I'm sorry, I responded too quickly without thinking about your question,
my mistake.  It isn't the prototype that was changed in the
CONFIG_SYSCALL case that is relevant in that case.

There was already in existance in the !CONFIG_AUDITSYSCALL case the
inline wrapper to do that job:

	static inline void audit_fanotify(u32 response, struct fanotify_response_info_audit_rule *friar)
	{ }

Did I understand correctly this time and does this answer your question?

But you do cause me to notice the case that these notifications will be
dropped when CONFIG_AUDIT && !CONFIG_AUDITSYSCALL.

Thanks for persisting.

> 								Honza
> 
> > diff --git a/include/linux/audit.h b/include/linux/audit.h
> > index 0050ef288ab3..d0c6f23503a1 100644
> > --- a/include/linux/audit.h
> > +++ b/include/linux/audit.h
> > @@ -418,7 +418,7 @@ extern void __audit_log_capset(const struct cred *new, const struct cred *old);
> >  extern void __audit_mmap_fd(int fd, int flags);
> >  extern void __audit_openat2_how(struct open_how *how);
> >  extern void __audit_log_kern_module(char *name);
> > -extern void __audit_fanotify(u32 response, struct fanotify_response_info_audit_rule *friar);
> > +extern void audit_fanotify(u32 response, struct fanotify_response_info_audit_rule *friar);
> >  extern void __audit_tk_injoffset(struct timespec64 offset);
> >  extern void __audit_ntp_log(const struct audit_ntp_data *ad);
> >  extern void __audit_log_nfcfg(const char *name, u8 af, unsigned int nentries,
> > 
> > > -- 
> > > Jan Kara <jack@...e.com>
> > > SUSE Labs, CR
> > 
> > - RGB
> > 
> -- 
> Jan Kara <jack@...e.com>
> SUSE Labs, CR

- RGB

--
Richard Guy Briggs <rgb@...hat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
Upstream IRC: SunRaycer
Voice: +1.613.860 2354 SMS: +1.613.518.6570