On Mon, Jan 31, 2022 at 6:29 PM Richard Guy Briggs <r...@redhat.com> wrote:
> On 2022-01-31 17:02, Paul Moore wrote:
> > On Wed, Jan 26, 2022 at 8:52 AM Richard Guy Briggs <r...@redhat.com>
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 <r...@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
> > > > 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);
>
> There is an audit_log_end() in the calling function, show_special(), so
> it should only be called here if there is another buffer allocated in
> this function after it. audit_log_end() is protected should it be
> called with no valid buffer so this wouldn't create a bug.
As audit_log_end() can safely take a NULL audit_buffer I don't care if we
send it back a valid buffer or a NULL. IMO it happens to be easier (and
cleaner) to send back a NULL.
> > if (*abp) {
> > *abp = NULL;
> > type = (type == AUDIT_TIME_ADJNTPVAL ?
> > AUDIT_TIME_INJOFFSET : AUDIT_TIME_ADJNTPVAL);
>
> This cannot be allocated if there are no more needed above ...
My mistake, I was distracted a few times while typing up my reply and the
code within; while I had that detail in mind when I started I lost it
during one of the interruptions. As penance, I wrote up some slightly more
proper code and at least made sure it complied, although I've not tried
booting it ...
diff --git a/kernel/audit.c b/kernel/audit.c
index e4bbe2c70c26..f21024d8a402 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1737,7 +1737,11 @@ static int __init audit_backlog_limit_set(char *str)
}
__setup("audit_backlog_limit=", audit_backlog_limit_set);
-static void audit_buffer_free(struct audit_buffer *ab)
+/**
+ * audit_buffer_free - free an audit buffer
+ * @ab: the audit buffer to free
+ */
+void audit_buffer_free(struct audit_buffer *ab)
{
if (!ab)
return;
diff --git a/kernel/audit.h b/kernel/audit.h
index c4498090a5bd..ba4c12b0d876 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -201,6 +201,10 @@ struct audit_context {
struct {
char *name;
} module;
+ struct {
+ struct audit_ntp_data ntp_data;
+ struct timespec64 tk_injoffset;
+ } time;
};
int fds[2];
struct audit_proctitle proctitle;
@@ -208,6 +212,8 @@ struct audit_context {
extern bool audit_ever_enabled;
+extern void audit_buffer_free(struct audit_buffer *ab);
+
extern void audit_log_session_info(struct audit_buffer *ab);
extern int auditd_test_task(struct task_struct *task);
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index fce5d43a933f..81434441aa13 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1340,6 +1340,76 @@ static void audit_log_fcaps(struct audit_buffer *ab,
struct audit_names *name)
from_kuid(&init_user_ns, name->fcap.rootid));
}
+/**
+ * audit_log_time - log ntp/time related information
+ * @context: the audit context
+ * @ab: an audit buffer
+ *
+ * This is a helper function for show_special() and should not be called
from
+ * any other context. This function also fully consumes @ab such that the
+ * caller should not assume it to be valid on return.
+ */
+static void audit_log_time(struct audit_context *context,
+ struct audit_buffer *ab)
+{
+ int i;
+ int type = context->type;
+ const char *ntp_name[] = {
+ "offset",
+ "freq",
+ "status",
+ "tai",
+ "tick",
+ "adjust",
+ };
+
+ do {
+ if (type == AUDIT_TIME_ADJNTPVAL) {
+ struct audit_ntp_val *ntp =
context->time.ntp_data.vals;
+
+ for (i = 0; i < AUDIT_NTP_NVALS; i++) {
+ if (ntp[i].newval == ntp[i].oldval)
+ continue;
+
+ if (!ab)
+ ab = audit_log_start(context,
+ GFP_KERNEL,
type);
+ audit_log_format(ab,
+ "op=%s old=%lli new=%lli",
+ ntp_name[i],
+ ntp[i].oldval,
ntp[i].newval);
+ audit_log_end(ab);
+ ab = NULL;
+ }
+
+ type = (type == context->type ?
+ AUDIT_TIME_INJOFFSET : 0);
+ } else if (type == AUDIT_TIME_INJOFFSET) {
+ struct timespec64 *tk = &context->time.tk_injoffset;
+
+ if (tk->tv_sec || tk->tv_nsec) {
+ if (!ab)
+ ab = audit_log_start(context,
+ GFP_KERNEL,
type);
+ audit_log_format(ab, "sec=%lli nsec=%li",
+ (long long)tk->tv_sec,
+ tk->tv_nsec);
+ audit_log_end(ab);
+ ab = NULL;
+ }
+
+ type = (type == context->type ?
+ AUDIT_TIME_ADJNTPVAL : 0);
+ } else
+ WARN_ONCE(1,
+ "audit_log_time() called with invalid
context (%d)\n",
+ context->type);
+ } while (type);
+
+ /* ab should always be NULL here, but cleanup _just_in_case_ ... */
+ audit_buffer_free(ab);
+}
+
static void show_special(struct audit_context *context, int *call_panic)
{
struct audit_buffer *ab;
@@ -1454,6 +1524,11 @@ static void show_special(struct audit_context
*context, int *call_panic)
audit_log_format(ab, "(null)");
break;
+ case AUDIT_TIME_ADJNTPVAL:
+ case AUDIT_TIME_INJOFFSET:
+ audit_log_time(context, ab);
+ ab = NULL;
+ break;
}
audit_log_end(ab);
}
@@ -2849,21 +2924,25 @@ void __audit_fanotify(unsigned int response)
void __audit_tk_injoffset(struct timespec64 offset)
{
- audit_log(audit_context(), GFP_KERNEL, AUDIT_TIME_INJOFFSET,
- "sec=%lli nsec=%li",
- (long long)offset.tv_sec, offset.tv_nsec);
+ struct audit_context *context = audit_context();
+
+ if (!context->type)
+ context->type = AUDIT_TIME_INJOFFSET;
+ memcpy(&context->time.tk_injoffset, &offset, sizeof(offset));
}
static void audit_log_ntp_val(const struct audit_ntp_data *ad,
const char *op, enum audit_ntp_type type)
{
- const struct audit_ntp_val *val = &ad->vals[type];
-
- if (val->newval == val->oldval)
- return;
+ int i;
+ struct audit_context *context = audit_context();
- audit_log(audit_context(), GFP_KERNEL, AUDIT_TIME_ADJNTPVAL,
- "op=%s old=%lli new=%lli", op, val->oldval, val->newval);
+ for (i = 0; i < AUDIT_NTP_NVALS; i++)
+ if (ad->vals[i].newval != ad->vals[i].oldval) {
+ context->type = AUDIT_TIME_ADJNTPVAL;
+ memcpy(&context->time.ntp_data, ad, sizeof(*ad));
+ break;
+ }
}
void __audit_ntp_log(const struct audit_ntp_data *ad)
--
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