linux-kernel - Re: [PATCH] hooks: fix a missing-check bug in selinux_sb_eat_lsm

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Date:   Thu, 30 May 2019 15:38:34 +0800
From:   Gen Zhang <blackgod016574@...il.com>
To:     William Roberts <bill.c.roberts@...il.com>
Cc:     Paul Moore <paul@...l-moore.com>, tony.luck@...el.com,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Eric Paris <eparis@...isplace.org>, selinux@...r.kernel.org,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH] hooks: fix a missing-check bug in
 selinux_sb_eat_lsm_opts()

On Wed, May 29, 2019 at 09:39:50PM -0700, William Roberts wrote:
> On Wed, May 29, 2019 at 8:55 PM Gen Zhang <blackgod016574@...il.com> 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@...il.com>
> > ---
> > 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 0;
> 
> The routine seems to return 0 on success, why would it return 0 on ENOMEM?
> 
Thanks for your reply, William. I re-examined the source code and didn't
figure out what the return value should be in this situation. Could it 
be a -ENOMEM? Do you have any idea?

Thanks
Gen
> >                         }
> >                         rc = selinux_add_opt(token, arg, mnt_opts);
> >                         if (unlikely(rc)) {