Re: [RFC PATCH 2/9] audit, io_uring, io-wq: add some basic audit support to io_uring

[Paul Moore <paul@paul-moore.com>]

On Tue, Aug 24, 2021 at 9:21 PM Richard Guy Briggs <rgb@redhat.com> wrote:
>
> On 2021-06-02 13:46, Paul Moore wrote:
> > On Wed, Jun 2, 2021 at 1:29 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > On 2021-05-21 17:49, Paul Moore wrote:
> > > > WARNING - This is a work in progress and should not be merged
> > > > anywhere important.  It is almost surely not complete, and while it
> > > > probably compiles it likely hasn't been booted and will do terrible
> > > > things.  You have been warned.
> > > >
> > > > This patch adds basic auditing to io_uring operations, regardless of
> > > > their context.  This is accomplished by allocating audit_context
> > > > structures for the io-wq worker and io_uring SQPOLL kernel threads
> > > > as well as explicitly auditing the io_uring operations in
> > > > io_issue_sqe().  The io_uring operations are audited using a new
> > > > AUDIT_URINGOP record, an example is shown below:
> > > >
> > > >   % <TODO - insert AUDIT_URINGOP record example>
> > > >
> > > > Thanks to Richard Guy Briggs for review and feedback.
> > > >
> > > > Signed-off-by: Paul Moore <paul@paul-moore.com>
> > > > ---
> > > >  fs/io-wq.c                 |    4 +
> > > >  fs/io_uring.c              |   11 +++
> > > >  include/linux/audit.h      |   17 ++++
> > > >  include/uapi/linux/audit.h |    1
> > > >  kernel/audit.h             |    2 +
> > > >  kernel/auditsc.c           |  173 ++++++++++++++++++++++++++++++++++++++++++++
> > > >  6 files changed, 208 insertions(+)

...

> > > > +     if (ctx->return_valid != AUDITSC_INVALID)
> > > > +             audit_log_format(ab, " success=%s exit=%ld",
> > > > +                              (ctx->return_valid == AUDITSC_SUCCESS ?
> > > > +                               "yes" : "no"),
> > > > +                              ctx->return_code);
> > > > +     audit_log_format(ab,
> > > > +                      " items=%d"
> > > > +                      " ppid=%d pid=%d auid=%u uid=%u gid=%u"
> > > > +                      " euid=%u suid=%u fsuid=%u"
> > > > +                      " egid=%u sgid=%u fsgid=%u",
> > > > +                      ctx->name_count,
> > > > +                      task_ppid_nr(current),
> > > > +                      task_tgid_nr(current),
> > > > +                      from_kuid(&init_user_ns, audit_get_loginuid(current)),
> > > > +                      from_kuid(&init_user_ns, cred->uid),
> > > > +                      from_kgid(&init_user_ns, cred->gid),
> > > > +                      from_kuid(&init_user_ns, cred->euid),
> > > > +                      from_kuid(&init_user_ns, cred->suid),
> > > > +                      from_kuid(&init_user_ns, cred->fsuid),
> > > > +                      from_kgid(&init_user_ns, cred->egid),
> > > > +                      from_kgid(&init_user_ns, cred->sgid),
> > > > +                      from_kgid(&init_user_ns, cred->fsgid));
> > >
> > > The audit session ID is still important, relevant and qualifies auid.
> > > In keeping with the SYSCALL record format, I think we want to keep
> > > ses=audit_get_sessionid(current) in here.
> >
> > This might be another case of syscall/io_uring confusion.  An io_uring
> > op doesn't necessarily have an audit session ID or an audit UID in the
> > conventional sense; for example think about SQPOLL works, shared
> > rings, etc.
>
> Right, but those syscalls are what instigate io_uring operations, so
> whatever process starts that operation, or gets handed that handle
> should be tracked with auid and sessionid (the two work together to
> track) unless we can easily track io_uring ops to connect them to a
> previous setup syscall.  If we see a need to keep the auid, then the
> sessionid goes with it.

As a reminder, once the io_uring is created appropriately one can
issue io_uring operations without making a syscall.  Further, sharing
a io_uring across process boundaries means that both the audit session
ID and audit login UID used to create the io_uring might not be the
same as the subject which issues operations to the io_uring.

Any io_uring operations that happen synchronously as the result of a
syscall should be associated with the SYSCALL record so the session ID
and login UID will be part of the event.  Asynchronous operations will
not have that information because we don't have a way to get it.

-- 
paul moore
www.paul-moore.com