Re: [PATCH v2] hooks: fix a missing-check bug in selinux_sb_eat_lsm_opts()

[William Roberts]

On Thu, May 30, 2019 at 4:52 AM Ondrej Mosnacek <omosnace@xxxxxxxxxx> wrote:
>
> On Thu, May 30, 2019 at 10:51 AM Gen Zhang <blackgod016574@xxxxxxxxx> wrote:
> > In selinux_sb_eat_lsm_opts(), 'arg' is allocated by kmemdup_nul(). It
> > returns NULL when fails. So 'arg' should be checked.
> >
> > Signed-off-by: Gen Zhang <blackgod016574@xxxxxxxxx>
> > Fixes: 99dbbb593fe6 ("selinux: rewrite selinux_sb_eat_lsm_opts()")
> > ---
> > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> > index 3ec702c..5a9e959 100644
> > --- a/security/selinux/hooks.c
> > +++ b/security/selinux/hooks.c
> > @@ -2635,6 +2635,8 @@ static int selinux_sb_eat_lsm_opts(char *options, void **mnt_opts)
> >                                                 *q++ = c;
> >                                 }
> >                                 arg = kmemdup_nul(arg, q - arg, GFP_KERNEL);
> > +                               if (!arg)
> > +                                       return -ENOMEM;

Yeah -ENOMEM is correct here. Ack by me.

> >                         }
> >                         rc = selinux_add_opt(token, arg, mnt_opts);
> >                         if (unlikely(rc)) {
>
> Looking at the callers of security_sb_eat_lsm_opts() (which is the
> function that eventually calls the selinux_sb_eat_lsm_opts() hook),
> -ENOMEM should be appropriate here.
>
> Reviewed-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
>
> --
> Ondrej Mosnacek <omosnace at redhat dot com>
> Software Engineer, Security Technologies
> Red Hat, Inc.