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

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Message-ID: <aDW5mI2dE7xOMMni@madcap2.tricolour.ca>
Date: Tue, 27 May 2025 09:09:44 -0400
From: Richard Guy Briggs <rgb@...hat.com>
To: Paul Moore <paul@...l-moore.com>
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>,
	Eric Paris <eparis@...isplace.org>, Steve Grubb <sgrubb@...hat.com>,
	Jan Kara <jack@...e.cz>, Amir Goldstein <amir73il@...il.com>
Subject: Re: [PATCH v1 1/2] audit: record fanotify event regardless of
 presence  of rules

On 2025-04-11 14:14, Paul Moore wrote:
> On Mar  5, 2025 Richard Guy Briggs <rgb@...hat.com> 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>
> > Acked-by: Jan Kara <jack@...e.cz>
> > ---
> >  include/linux/audit.h | 8 +-------
> >  kernel/auditsc.c      | 2 +-
> >  2 files changed, 2 insertions(+), 8 deletions(-)
> > 
> > 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,
> > @@ -525,12 +525,6 @@ static inline void audit_log_kern_module(char *name)
> >  		__audit_log_kern_module(name);
> >  }
> >  
> > -static inline void audit_fanotify(u32 response, struct fanotify_response_info_audit_rule *friar)
> > -{
> > -	if (!audit_dummy_context())
> > -		__audit_fanotify(response, friar);
> > -}
> 
> It seems like we should at least have an audit_enabled() check, yes?
> We've had people complain about audit events being generated when audit
> is disabled, any while we don't currently have such a check in place
> here, I believe the dummy context check is doing that for us.
> 
>   static inline void audit_fanotify(...)
>   {
>     if (!audit_enabled)
>       return;
>     __audit_fanotify(...);
>   }

That would be consistent with other security events messages.  I was
going through the selinux code to see what it does and I am missing it
if selinux checks with audit_enabled().  Are selinux messages somehow
exempt from audit_enabled()?

> >  static inline void audit_tk_injoffset(struct timespec64 offset)
> >  {
> >  	/* ignore no-op events */
> > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > index 0627e74585ce..936825114bae 100644
> > --- a/kernel/auditsc.c
> > +++ b/kernel/auditsc.c
> > @@ -2880,7 +2880,7 @@ void __audit_log_kern_module(char *name)
> >  	context->type = AUDIT_KERN_MODULE;
> >  }
> >  
> > -void __audit_fanotify(u32 response, struct fanotify_response_info_audit_rule *friar)
> > +void audit_fanotify(u32 response, struct fanotify_response_info_audit_rule *friar)
> >  {
> >  	/* {subj,obj}_trust values are {0,1,2}: no,yes,unknown */
> >  	switch (friar->hdr.type) {
> > -- 
> > 2.43.5
> 
> --
> paul-moore.com
> 

- 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