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

Paul Moore
2019-05-29T22:16:18Z

On Mon, Apr 8, 2019 at 11:41 PM Richard Guy Briggs <rgb@redhat.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@redhat.com>
> Acked-by: Serge Hallyn <serge@hallyn.com>
> Acked-by: Neil Horman <nhorman@tuxdriver.com>
> Reviewed-by: Ondrej Mosnacek <omosnace@redhat.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