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

On Wed, Jan 26, 2022 at 8:52 AM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > 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; Honestly, I've looked at this a few times over different days trying to make sure I'm not missing something, but there is a lot of complexity in audit_log_time() that I don't believe is necessary. What about something like below? [WARNING: not compiled, tested, yadda yadda] void audit_log_time(struct audit_context ctx, struct audit_buffer **abp) { int i; int type = ctx->type; struct audit_buffer *ab = *abp; struct audit_ntp_val *ntp; const struct timespec64 *tk; const char *ntp_name[] = { "offset", "freq", "status", "tai", "tick", "adjust", }; do { if (type == AUDIT_TIME_ADJNTPVAL) { ntp = ctx->time.ntp_data.val; for (i = 0; i < AUDIT_NTP_NVALS; i++) { if (ntp[i].newval != ntp[i].oldval) { audit_log_format(ab, "op=%s old=%lli new=%lli", ntp_name[type], ntp[i].oldval, ntp[i].newval); } } } else { tk = &ctx->time.tk_injoffset; audit_log_format(ab, "sec=%lli nsec=%li", (long long)tk->tv_sec, tk->tv_nsec); } audit_log_end(ab);

if (*abp) { *abp = NULL; type = (type == AUDIT_TIME_ADJNTPVAL ? AUDIT_TIME_INJOFFSET : AUDIT_TIME_ADJNTPVAL);

ab = audit_log_start(ctx, GFP_KERNEL, type); } else ab = NULL; } while (ab); } > > + 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; Not something I would normally worry about, but since you're probably going to respin this anyway you might as well change the 'break;' to 'return;'.

> > + } paul-moore.com