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

On 14/11/13, Paul Moore wrote: > On Thursday, November 13, 2014 03:29:10 PM 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. > > > > Since "version" is too generic to convert with a #define, use a union in the > > struct status, introducing the member "feature_bitmap" unionized with > > "version". > > > > Convert existing AUDIT_VERSION_* macros over to AUDIT_FEATURE_BITMAP* > > counterparts, leaving the former for backwards compatibility. > > > > Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; > > --- > > include/uapi/linux/audit.h | 17 +++++++++++++---- > > kernel/audit.c | 2 +- > > 2 files changed, 14 insertions(+), 5 deletions(-) > > Looks good for the most part, just a naming nit pick and a question about the > deprecated AUDIT_VERSION_* defines; see below ... > > > diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h > > index 4d100c8..74aa584 100644 > > --- 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 ) > > How about AUDIT_FEATURE_BIMAP_ALL instead of just AUDIT_FEATURE_BITMAP? Sure, I'm fine with that. > > +/* 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 > > So what terrible things happen to userspace if AUDIT_VERSION_BACKLOG_WAIT_TIME > becomes 0x03 instead of 0x02? But it won't. It gets the value of AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME, which is 0x00000002. I think you meant to ask about AUDIT_VERSION_LATEST, which would become 3. You *did* already ask that question in a previous thread, and there didn't seem to be a concern. Steve Grubb could likely answer this question better than me. > paul moore - RGB -- Richard Guy Briggs <rbriggs(a)redhat.com&gt; 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/