linux-kernel - Re: [PATCH] audit: catch errors from audit_filter

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Date:	Thu, 16 Jun 2016 17:07:37 -0400
From:	Paul Moore <paul@...l-moore.com>
To:	Richard Guy Briggs <rgb@...hat.com>
Cc:	linux-audit@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] audit: catch errors from audit_filter_rules field checks

On Tue, Jun 14, 2016 at 5:03 PM, Richard Guy Briggs <rgb@...hat.com> wrote:
> In the case of an error returned from a field check in an audit filter
> syscall rule, it is treated as a match and the rule action is honoured.
>
> This could cause a rule with a default of NEVER and an selinux field
> check error to avoid logging.
>
> Recommend matching with an action of ALWAYS to catch malicious abuse of
> this bug.  The downside of this approach is it could DoS the audit
> subsystem.

I understand your concern about the DoS, but in reality it is no worse
than if no audit filter rules were configured, yes?

> Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> ---
>  kernel/auditsc.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 71e14d8..6123672 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -683,6 +683,10 @@ static int audit_filter_rules(struct task_struct *tsk,
>                 }
>                 if (!result)
>                         return 0;
> +               if (result < 0) {
> +                       *state = AUDIT_RECORD_CONTEXT;
> +                       return 1;
> +               }
>         }
>
>         if (ctx) {

-- 
paul moore
www.paul-moore.com