linux-kernel - Re: [PATCH] audit: skip sessionid sentinel value when auto-incrementing

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Message-ID: <CAHC9VhQHobqD8q5+OneX5Gd4fQwvgbWp+k+EvvJtXPB8vg78ZQ@mail.gmail.com>
Date:   Thu, 17 Nov 2016 18:34:47 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     linux-audit@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] audit: skip sessionid sentinel value when auto-incrementing

On Tue, Nov 15, 2016 at 3:49 AM, Richard Guy Briggs <rgb@...hat.com> wrote:
> On 2016-11-14 15:17, Paul Moore wrote:
>> On Thu, Nov 10, 2016 at 1:41 AM, Richard Guy Briggs <rgb@...hat.com> wrote:
>> > The value (unsigned int)-1 is used as a sentinel to indicate the
>> > sessionID is unset.  Skip this value when the session_id value wraps.
>> >
>> > Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
>> > ---
>> >  kernel/auditsc.c |    5 ++++-
>> >  1 files changed, 4 insertions(+), 1 deletions(-)
>>
>> Since we haven't merged the session ID kernel patches into audit#next
>> yet, why don't you just squash this patch in with the session ID patch
>> and resubmit upstream in one nice neat patch.
>
> This was an existing bug regardless of new functionality added, so the
> fix should not be buried in a new feature patch.

No, it's not an existing bug.  The existing code simply reports/logs
the session ID, it doesn't filter on it, so there are no magic values
to worry about.

>> > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
>> > index 5abf1dc..e414dfa 100644
>> > --- a/kernel/auditsc.c
>> > +++ b/kernel/auditsc.c
>> > @@ -2025,8 +2025,11 @@ int audit_set_loginuid(kuid_t loginuid)
>> >                 goto out;
>> >
>> >         /* are we setting or clearing? */
>> > -       if (uid_valid(loginuid))
>> > +       if (uid_valid(loginuid)) {
>> >                 sessionid = (unsigned int)atomic_inc_return(&session_id);
>> > +               if (unlikely(sessionid == (unsigned int)-1))
>> > +                       sessionid = (unsigned int)atomic_inc_return(&session_id);
>> > +       }
>> >
>> >         task->sessionid = sessionid;
>> >         task->loginuid = loginuid;
>>
>> paul moore
>
> - RGB
>
> --
> Richard Guy Briggs <rgb@...hat.com>
> Kernel Security Engineering, Base Operating Systems, Red Hat
> Remote, Ottawa, Canada
> Voice: +1.647.777.2635, Internal: (81) 32635



-- 
paul moore
www.paul-moore.com