Re: [PATCH] audit: convert status version to a feature bitmap

Richard Guy Briggs
2014-11-14T01:01:45Z

On 14/11/13, Joe Perches wrote:
> On Thu, 2014-11-13 at 15:29 -0500, Richard Guy Briggs wrote:
> > The version field defined in the audit status structure was found to have
> > limitations in terms of its expressibility of features supported. This is
> > distict from the get/set features call to be able to command those features
> > that are present.
> >
> > Converting this field from a version number to a feature bitmap will allow
> > distributions to selectively backport and support certain features and will
> > allow upstream to be able to deprecate features in the future. It will allow
> > userspace clients to first query the kernel for which features are actually
> > present and supported. Currently, EINVAL is returned rather than EOPNOTSUP,
> > which isn't helpful in determining if there was an error in the command, or if
> > it simply isn't supported yet. Past features are not represented by this
> > bitmap, but their use may be converted to EOPNOTSUP if needed in the future.
>
> Maybe use DECLARE_BITMAP instead of u32 and test_bit/set_bit

I don't think so. I'd like to code to be readable... I certainly don't
need the overhead of test/set_bit. That doesn't look appropriate for
anything in include/uapi/.

> > diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
>
> > @@ -322,9 +322,15 @@ enum {
> > #define AUDIT_STATUS_BACKLOG_LIMIT 0x0010
> > #define AUDIT_STATUS_BACKLOG_WAIT_TIME 0x0020
> >
> > -#define AUDIT_VERSION_BACKLOG_LIMIT 1
> > -#define AUDIT_VERSION_BACKLOG_WAIT_TIME 2
> > -#define AUDIT_VERSION_LATEST AUDIT_VERSION_BACKLOG_WAIT_TIME
> > +#define AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT 0x00000001
> > +#define AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME 0x00000002
> > +#define AUDIT_FEATURE_BITMAP ( AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT | \
> > + AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME )
> > +
> > +/* deprecated: AUDIT_VERSION_* */
> > +#define AUDIT_VERSION_LATEST AUDIT_FEATURE_BITMAP
> > +#define AUDIT_VERSION_BACKLOG_LIMIT AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT
> > +#define AUDIT_VERSION_BACKLOG_WAIT_TIME AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME
> >
> > /* Failure-to-log actions */
> > #define AUDIT_FAIL_SILENT 0
> > @@ -403,7 +409,10 @@ struct audit_status {
> > __u32 backlog_limit; /* waiting messages limit */
> > __u32 lost; /* messages lost */
> > __u32 backlog; /* messages waiting in queue */
> > - __u32 version; /* audit api version number */
> > + union {
> > + __u32 version; /* deprecated: audit api version num */
> > + __u32 feature_bitmap; /* bitmap of kernel audit features */
> > + };
> > __u32 backlog_wait_time;/* message queue wait timeout */
> > };
> >
> > diff --git a/kernel/audit.c b/kernel/audit.c
> > index 8ee4508..c9d0e30 100644
> > --- a/kernel/audit.c
> > +++ b/kernel/audit.c
> > @@ -842,7 +842,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
> > s.backlog_limit = audit_backlog_limit;
> > s.lost = atomic_read(&audit_lost);
> > s.backlog = skb_queue_len(&audit_skb_queue);
> > - s.version = AUDIT_VERSION_LATEST;
> > + s.feature_bitmap = AUDIT_FEATURE_BITMAP;
> > s.backlog_wait_time = audit_backlog_wait_time;
> > audit_send_reply(skb, seq, AUDIT_GET, 0, 0, &s, sizeof(s));
> > break;

- RGB

--
Richard Guy Briggs <rbriggs@redhat.com>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545