Re: Lost events during boot

On Mon, Mar 20, 2017 at 10:44 AM, Paul Moore <paul(a)paul-moore.com&gt; wrote: > On Mon, Mar 20, 2017 at 8:08 AM, Paul Moore <paul(a)paul-moore.com&gt; wrote: >> On Sun, Mar 19, 2017 at 9:46 PM, Steve Grubb <sgrubb(a)redhat.com&gt; wrote: >>> Hello Richard and Paul, >>> >>> I was going to do a blog write up about booting the system with >>> audit_backlog_limit=8192 for STIG users and have stumbled on to a >>> mystery. The kernel initializes the variable to 64 at power on. During >>> boot, if audit == 1, then it holds events in the hopes that an audit >>> daemon will show up later and drain all the events. Anything over 64 >>> events should fall off the end and increment the lost counter and put a >>> notice in syslog. >>> >>> However, when booting with audit_backlog_limit=8192, as soon as I log in >>> I run "auditctl -s" I can see I've lost 73 events. The I run "aureport >>> --start boot" and I see 644 total events. This is nowhere near the 8192 >>> limit that I asked for. So, why am I losing events? >>> >>> Additionally, I checked the logs and there is absolutely no message in >>> syslog showing that I've lost events. This is with failure mode set to >>> 1 - which is default at power on. And this is in spite of the the fact >>> that the source code seems to show that it should have printk'ed >>> something. >>> >>> Any ideas? Can you replicate this finding? >> >> It's funny, I just noticed this for the first time on Friday (the >> exact same lost count too), although it was a development kernel build >> with a *heavily* modified audit subsystem so I just assumed I had >> broken something with the queuing, the lost counter, or both. It's >> possible I still may have broken something in the v4.10 queue rework, >> or something broke a long time ago and we are just noticing it now. >> >> First off, can you create a GitHub issue for this and include your >> kernel build (e.g. 'uname -r')? Second, if you are seeing this on a >> +v4.10 kernel, do you see the same results with a +v4.9 kernel? > > Quick follow-up, and completely untested, but it would appear that the > problem lies in kauditd_hold_skb()/kauditd_print_skb(); > kauditd_print_skb() registers a false lost record when the printk > ratelimit is tripped. The fix is rather simple, and I'll include that > in an upcoming patchset. ... and a quick question, if the kernel is booted without "audit=1" do we want to count lost records in the case where the backlog overflows?