Re: [PATCH v2] audit: log AUDIT_TIME_* records only from rules
On 2022-01-24 22:11, Paul Moore wrote:
On Fri, Jan 21, 2022 at 11:17 AM Richard Guy Briggs
<rgb(a)redhat.com> wrote:
>
> AUDIT_TIME_* events are generated when there are syscall rules present that are
> not related to time keeping. This will produce noisy log entries that could
> flood the logs and hide events we really care about.
>
> Rather than immediately produce the AUDIT_TIME_* records, store the data in the
> context and log it at syscall exit time respecting the filter rules.
>
> Please see https://bugzilla.redhat.com/show_bug.cgi?id=1991919
>
> Fixes: 7e8eda734d30 ("ntp: Audit NTP parameters adjustment")
> Fixes: 2d87a0674bd6 ("timekeeping: Audit clock adjustments")
> Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com>
> ---
> Changelog:
> v2:
> - rename __audit_ntp_log_ to audit_log_ntp
> - pre-check ntp before storing
> - move tk out of the context union and move ntp logging to the bottom of
audit_show_special()
> - restructure logging of ntp to use ab and allocate more only if more
> - add Fixes lines
>
> kernel/audit.h | 2 ++
> kernel/auditsc.c | 77 +++++++++++++++++++++++++++++++++++-------------
> 2 files changed, 59 insertions(+), 20 deletions(-)
>
> diff --git a/kernel/audit.h b/kernel/audit.h
> index c4498090a5bd..11789249d838 100644
> --- a/kernel/audit.h
> +++ b/kernel/audit.h
> @@ -201,8 +201,10 @@ struct audit_context {
> struct {
> char *name;
> } module;
> + struct audit_ntp_data ntp_data;
> };
> int fds[2];
> + struct timespec64 tk_injoffset;
> struct audit_proctitle proctitle;
> };
Why do we need to keep tk_injoffset outside of the audit_context
union? I think we could do something like this, which would be an
improvement IMO:
I did three implementations. The first put ntp_data outside which was
the quickest and simplest patch, but I really didn't like the wastage in
audit_context. The second did as you suggest below in the union, but
having the type overwritten by the other AUDIT_TIME_* didn't sit well
with me, but since we have to check all the values anyways, we don't
really lose anything. This means restructuring the loop a bit but that
should work. Both types will need to be written to the context->type.
I'll code that up...
struct audit_context {
/* ... */
union {
/* ... */
struct {
struct audit_ntp_data ntp_data;
struct timespec64 tk_injoffset;
} time;
};
/* ... */
}
void __audit_tk_injoffset(offset)
{
struct audit_context *ctx = audit_context();
memcpy(&ctx->time->tk_injoffset, offset, sizeof(offset));
}
void audit_log_time(ctx)
{
/* ... */
offset = ctx->time->tk_injoffset;
if (offset->tv_sec != 0 || offset->tv_nsec != 0) {
ab = audit_log_start(ctx, GFP_KERNEL, AUDIT_TIME_INJOFFSET);
/* ... */
audit_log_end(ab);
}
ntp = ctx->time->ntp_data;
for (i = 0; i < AUDIT_NTP_NVALS; i++) {
if (ntp->vals[i].newval != ntp->vals[i].oldval ) {
/* ... log the ntp/time param changes ... */
}
}
/* ... */
}
void show_special(...)
{
/* ... */
case AUDIT_TIME_INJOFFSET:
case AUDIT_TIME_ADJNTPVAL:
audit_log_time(context);
break;
/* ... */
}
--
paul moore
paul-moore.com
- RGB
--
Richard Guy Briggs <rgb(a)redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635