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Date: Tue, 23 Jul 2019 08:48:12 +0200
From: Ondrej Mosnacek <omosnace@...hat.com>
To: William Roberts <bill.c.roberts@...il.com>
Cc: SElinux list <selinux@...r.kernel.org>, Paul Moore <paul@...l-moore.com>, 
	NitinGote <nitin.r.gote@...el.com>, kernel-hardening@...ts.openwall.com, 
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] selinux: check sidtab limit before adding a new entry

On Mon, Jul 22, 2019 at 4:17 PM William Roberts
<bill.c.roberts@...il.com> wrote:
> On Mon, Jul 22, 2019 at 8:34 AM Ondrej Mosnacek <omosnace@...hat.com> wrote:
> >
> > We need to error out when trying to add an entry above SIDTAB_MAX in
> > sidtab_reverse_lookup() to avoid overflow on the odd chance that this
> > happens.
> >
> > Fixes: ee1a84fdfeed ("selinux: overhaul sidtab to fix bug and improve performance")
> > Signed-off-by: Ondrej Mosnacek <omosnace@...hat.com>
> > ---
> >  security/selinux/ss/sidtab.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/security/selinux/ss/sidtab.c b/security/selinux/ss/sidtab.c
> > index e63a90ff2728..54c1ba1e79ab 100644
> > --- a/security/selinux/ss/sidtab.c
> > +++ b/security/selinux/ss/sidtab.c
> > @@ -286,6 +286,11 @@ static int sidtab_reverse_lookup(struct sidtab *s, struct context *context,
> >                 ++count;
> >         }
> >
> > +       /* bail out if we already reached max entries */
> > +       rc = -ENOMEM;
>
> Wouldn't -EOVERFLOW be better?

Good point. Will change it in v2.

>
> > +       if (count == SIDTAB_MAX)
> > +               goto out_unlock;
> > +
> >         /* insert context into new entry */
> >         rc = -ENOMEM;
> >         dst = sidtab_do_lookup(s, count, 1);
> > --
> > 2.21.0
> >

Thanks,
-- 
Ondrej Mosnacek <omosnace at redhat dot com>
Software Engineer, Security Technologies
Red Hat, Inc.

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