Re: [PATCH 1/2] audit: show user land backtrace as part of audit context messages
On Tue, Feb 2, 2021 at 10:46 PM Paul Moore <paul(a)paul-moore.com> wrote:
On Tue, Feb 2, 2021 at 4:44 PM Daniel Walker (danielwa)
<danielwa(a)cisco.com> wrote:
> On Tue, Feb 02, 2021 at 04:35:42PM -0500, Paul Moore wrote:
> > On Tue, Feb 2, 2021 at 4:29 PM Daniel Walker <danielwa(a)cisco.com> wrote:
> > > From: Victor Kamensky <kamensky(a)cisco.com>
> > >
> > > To efficiently find out where SELinux AVC denial is comming from
> > > take backtrace of user land process and display it as type=UBACKTRACE
> > > message that comes as audit context for SELinux AVC and other audit
> > > messages ...
> >
> > Have you tried the new perf tracepoint for SELinux AVC decisions that
> > trigger an audit event? It's a new feature for v5.10 and looks to
> > accomplish most of what you are looking for with this patch.
> >
> > * https://www.paul-moore.com/blog/d/2020/12/linux_v510.html
>
> We haven't tried it, but I can look into it. We're not using v5.10
extensively
> yet.
Let us know if that works for you, and if it doesn't, let us know what
might be missing. I hate seeing the kernel grow multiple features
which do the same thing.
I agree - I played around with this new tracepoint recently and you
can use it to achieve what you want quite easily:
# collect traces for denials (just interrupt/kill the sleep process
when done) - will create a perf.data file you can analyze later
perf record -a -e avc:selinux_audited -g --call-graph=dwarf sleep infinity
# dump all collected backtraces from the perf.data file
perf script
It's a bit complicated if you want to have it running in the
background permanently as a service (you need to tell perf to dump the
recorded data before you can read it), but perf already has some
command-line options to help with that use case.
--
Ondrej Mosnacek
Software Engineer, Linux Security - SELinux kernel
Red Hat, Inc.