Re: [PATCH v3] audit: log AUDIT_TIME_* records only from rules

On 2022-01-25 22:24, Richard Guy Briggs 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&gt; > --- > 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 > v3 > - move tk into union > - rename audit_log_ntp() to audit_log_time() and add tk > - key off both AUDIT_TIME_* but favour NTP > > kernel/audit.h | 4 +++ > kernel/auditsc.c | 86 +++++++++++++++++++++++++++++++++++++----------- > 2 files changed, 70 insertions(+), 20 deletions(-)

> diff --git a/kernel/auditsc.c b/kernel/auditsc.c > index b517947bfa48..9c6c55a81fdb 100644 > --- a/kernel/auditsc.c > +++ b/kernel/auditsc.c > @@ -1331,6 +1331,55 @@ static void audit_log_fcaps(struct audit_buffer *ab, struct audit_names *name) > from_kuid(&init_user_ns, name->fcap.rootid)); > } > > +void audit_log_time(struct audit_context *context, struct audit_buffer **ab) > +{ > + const struct audit_ntp_data *ntp = &context->time.ntp_data; > + const struct timespec64 *tk = &context->time.tk_injoffset; > + const char *ntp_name[] = { > + "offset", > + "freq", > + "status", > + "tai", > + "tick", > + "adjust", > + }; > + int type, first = 1; > + > + if (context->type == AUDIT_TIME_INJOFFSET) > + goto tk; > + > + /* use up allocated ab from show_special before new one */ > + for (type = 0; type < AUDIT_NTP_NVALS; type++) { > + if (ntp->vals[type].newval != ntp->vals[type].oldval) { > + if (first) { > + first = 0; > + } else { > + audit_log_end(*ab); > + *ab = audit_log_start(context, GFP_KERNEL, > + AUDIT_TIME_ADJNTPVAL); > + if (!*ab) > + return; > + } > + audit_log_format(*ab, "op=%s old=%lli new=%lli", > + ntp_name[type], ntp->vals[type].oldval, > + ntp->vals[type].newval); > + } > + } > + > +tk: > + if (tk->tv_sec != 0 || tk->tv_nsec != 0) { > + if (!first) { > + audit_log_end(*ab); > + *ab = audit_log_start(context, GFP_KERNEL, > + AUDIT_TIME_INJOFFSET); > + if (!*ab) > + return; > + } It occurs to me that a slight improvement could be made to move the "tk:" label here. And better yet, change the tk condition above to: if (!tk->tv_sec && !tk->tv_nsec) return;

> + audit_log_format(*ab, "sec=%lli nsec=%li", > + (long long)tk->tv_sec, tk->tv_nsec); > + } > +}

> void __audit_ntp_log(const struct audit_ntp_data *ad) > { > - audit_log_ntp_val(ad, "offset", AUDIT_NTP_OFFSET); > - audit_log_ntp_val(ad, "freq", AUDIT_NTP_FREQ); > - audit_log_ntp_val(ad, "status", AUDIT_NTP_STATUS); > - audit_log_ntp_val(ad, "tai", AUDIT_NTP_TAI); > - audit_log_ntp_val(ad, "tick", AUDIT_NTP_TICK); > - audit_log_ntp_val(ad, "adjust", AUDIT_NTP_ADJUST); > + struct audit_context *context = audit_context(); > + int type; > + > + for (type = 0; type < AUDIT_NTP_NVALS; type++) > + if (ad->vals[type].newval != ad->vals[type].oldval) { > + context->type = AUDIT_TIME_ADJNTPVAL; > + memcpy(&context->time.ntp_data, ad, sizeof(*ad)); > + break;

> + }