linux-kernel - Re: [PATCH v4 3/4] fanotify,audit: Allow audit to use the full permission event response

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Date:   Wed, 31 Aug 2022 17:07:25 -0400
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Steve Grubb <sgrubb@...hat.com>, Paul Moore <paul@...l-moore.com>
Cc:     Linux-Audit Mailing List <linux-audit@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, Eric Paris <eparis@...isplace.org>,
        Jan Kara <jack@...e.cz>, Amir Goldstein <amir73il@...il.com>
Subject: Re: [PATCH v4 3/4] fanotify,audit: Allow audit to use the full
 permission event response

On 2022-08-15 20:22, Paul Moore wrote:
> On Tue, Aug 9, 2022 at 1:23 PM Richard Guy Briggs <rgb@...hat.com> wrote:
> >
> > This patch passes the full value so that the audit function can use all
> > of it. The audit function was updated to log the additional information in
> > the AUDIT_FANOTIFY record. The following is an example of the new record
> > format:
> >
> > type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1 fan_info=17
> >
> > Suggested-by: Steve Grubb <sgrubb@...hat.com>
> > Link: https://lore.kernel.org/r/3075502.aeNJFYEL58@x2
> > Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> > ---
> >  fs/notify/fanotify/fanotify.c |  3 ++-
> >  include/linux/audit.h         |  9 +++++----
> >  kernel/auditsc.c              | 31 ++++++++++++++++++++++++++++---
> >  3 files changed, 35 insertions(+), 8 deletions(-)
> 
> You've hopefully already seen the kernel test robot build warning, so
> I won't bring that up again, but a few comments below ...

Yes, dealt with...

...

> > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > index 433418d73584..f000fec52360 100644
> > --- a/kernel/auditsc.c
> > +++ b/kernel/auditsc.c
> > @@ -64,6 +64,7 @@
> >  #include <uapi/linux/limits.h>
> >  #include <uapi/linux/netfilter/nf_tables.h>
> >  #include <uapi/linux/openat2.h> // struct open_how
> > +#include <uapi/linux/fanotify.h>
> >
> >  #include "audit.h"
> >
> > @@ -2899,10 +2900,34 @@ void __audit_log_kern_module(char *name)
> >         context->type = AUDIT_KERN_MODULE;
> >  }
> >
> > -void __audit_fanotify(u32 response)
> > +void __audit_fanotify(u32 response, size_t len, char *buf)
> >  {
> > -       audit_log(audit_context(), GFP_KERNEL,
> > -               AUDIT_FANOTIFY, "resp=%u", response);
> > +       struct fanotify_response_info_audit_rule *friar;
> > +       size_t c = len;
> > +       char *ib = buf;
> > +
> > +       if (!(len && buf)) {
> > +               audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY,
> > +                         "resp=%u fan_type=0 fan_info=?", response);
> > +               return;
> > +       }
> > +       while (c >= sizeof(struct fanotify_response_info_header)) {
> > +               friar = (struct fanotify_response_info_audit_rule *)buf;
> 
> Since the only use of this at the moment is the
> fanotify_response_info_rule, why not pass the
> fanotify_response_info_rule struct directly into this function?  We
> can always change it if we need to in the future without affecting
> userspace, and it would simplify the code.

Steve, would it make any sense for there to be more than one
FAN_RESPONSE_INFO_AUDIT_RULE header in a message?  Could there be more
than one rule that contributes to a notify reason?  If not, would it be
reasonable to return -EINVAL if there is more than one?

> > +               switch (friar->hdr.type) {
> > +               case FAN_RESPONSE_INFO_AUDIT_RULE:
> > +                       if (friar->hdr.len < sizeof(*friar)) {
> > +                               audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY,
> > +                                         "resp=%u fan_type=%u fan_info=(incomplete)",
> > +                                         response, friar->hdr.type);
> > +                               return;
> > +                       }
> > +                       audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY,
> > +                                 "resp=%u fan_type=%u fan_info=%u",
> > +                                 response, friar->hdr.type, friar->audit_rule);
> > +               }
> > +               c -= friar->hdr.len;
> > +               ib += friar->hdr.len;
> > +       }
> >  }
> >
> >  void __audit_tk_injoffset(struct timespec64 offset)
> 
> 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