linux-kernel - Re: [PATCH ghak90 V6 08/10] audit: add containerid filtering

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Message-ID: <CAHC9VhRV-0LSEcRvPO1uXtKdpEQsaLZnBV3T=zcMTZPN5ugz5w@mail.gmail.com>
Date:   Wed, 29 May 2019 18:16:18 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     containers@...ts.linux-foundation.org, linux-api@...r.kernel.org,
        Linux-Audit Mailing List <linux-audit@...hat.com>,
        linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        sgrubb@...hat.com, omosnace@...hat.com, dhowells@...hat.com,
        simo@...hat.com, Eric Paris <eparis@...isplace.org>,
        Serge Hallyn <serge@...lyn.com>, ebiederm@...ssion.com,
        nhorman@...driver.com
Subject: Re: [PATCH ghak90 V6 08/10] audit: add containerid filtering

On Mon, Apr 8, 2019 at 11:41 PM Richard Guy Briggs <rgb@...hat.com> wrote:
>
> Implement audit container identifier filtering using the AUDIT_CONTID
> field name to send an 8-character string representing a u64 since the
> value field is only u32.
>
> Sending it as two u32 was considered, but gathering and comparing two
> fields was more complex.
>
> The feature indicator is AUDIT_FEATURE_BITMAP_CONTAINERID.
>
> Please see the github audit kernel issue for the contid filter feature:
>   https://github.com/linux-audit/audit-kernel/issues/91
> Please see the github audit userspace issue for filter additions:
>   https://github.com/linux-audit/audit-userspace/issues/40
> Please see the github audit testsuiite issue for the test case:
>   https://github.com/linux-audit/audit-testsuite/issues/64
> Please see the github audit wiki for the feature overview:
>   https://github.com/linux-audit/audit-kernel/wiki/RFE-Audit-Container-ID
> Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> Acked-by: Serge Hallyn <serge@...lyn.com>
> Acked-by: Neil Horman <nhorman@...driver.com>
> Reviewed-by: Ondrej Mosnacek <omosnace@...hat.com>
> ---
>  include/linux/audit.h      |  1 +
>  include/uapi/linux/audit.h |  5 ++++-
>  kernel/audit.h             |  1 +
>  kernel/auditfilter.c       | 47 ++++++++++++++++++++++++++++++++++++++++++++++
>  kernel/auditsc.c           |  4 ++++
>  5 files changed, 57 insertions(+), 1 deletion(-)

...

> diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> index 63f8b3f26fab..407b5bb3b4c6 100644
> --- a/kernel/auditfilter.c
> +++ b/kernel/auditfilter.c
> @@ -1206,6 +1224,31 @@ int audit_comparator(u32 left, u32 op, u32 right)
>         }
>  }
>
> +int audit_comparator64(u64 left, u32 op, u64 right)
> +{
> +       switch (op) {
> +       case Audit_equal:
> +               return (left == right);
> +       case Audit_not_equal:
> +               return (left != right);
> +       case Audit_lt:
> +               return (left < right);
> +       case Audit_le:
> +               return (left <= right);
> +       case Audit_gt:
> +               return (left > right);
> +       case Audit_ge:
> +               return (left >= right);
> +       case Audit_bitmask:
> +               return (left & right);
> +       case Audit_bittest:
> +               return ((left & right) == right);
> +       default:
> +               BUG();

A little birdy mentioned the BUG() here as a potential issue and while
I had ignored it in earlier patches because this is likely a
cut-n-paste from another audit comparator function, I took a closer
look this time.  It appears as though we will never have an invalid op
value as audit_data_to_entry()/audit_to_op() ensure that the op value
is a a known good value.  Removing the BUG() from all the audit
comparators is a separate issue, but I think it would be good to
remove it from this newly added comparator; keeping it so that we
return "0" in the default case seems reasoanble.

> +               return 0;
> +       }
> +}

--
paul moore
www.paul-moore.com