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

Joe Perches
2014-11-13T20:38:17Z

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

> 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;