linux-kernel - Re: [PATCH 2/2] LSM: SafeSetID: Add setgroups() security policy handling

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Message-ID: <202206131643.4FB2340C43@keescook>
Date:   Mon, 13 Jun 2022 16:46:29 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Micah Morton <mortonm@...omium.org>
Cc:     linux-security-module@...r.kernel.org, jmorris@...ei.org,
        serge@...lyn.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] LSM: SafeSetID: Add setgroups() security policy
 handling

On Mon, Jun 13, 2022 at 02:00:03PM -0700, Micah Morton wrote:
> On Mon, Jun 13, 2022 at 1:28 PM Micah Morton <mortonm@...omium.org> wrote:
> [...]
> > +static int safesetid_task_fix_setgroups(struct cred *new, const struct cred *old)
> > +{
> > +       int i;
> > +
> > +       /* Do nothing if there are no setgid restrictions for our old RGID. */
> > +       if (setid_policy_lookup((kid_t){.gid = old->gid}, INVALID_ID, GID) == SIDPOL_DEFAULT)
> > +               return 0;
> > +
> > +       get_group_info(new->group_info);
> > +       for (i = 0; i < new->group_info->ngroups; i++) {
> > +               if (!id_permitted_for_cred(old, (kid_t){.gid = group_info->gid[i]}, GID)) {
> 
> Oops, should be:
> 
> !id_permitted_for_cred(old, (kid_t){.gid = new->group_info->gid[i]}, GID)
> 
> Guess I won't send a whole new patch just for that one line

This begs the question: are there self-tests for this LSM somewhere?
It'd be really nice to add them to tool/testing/selftests ...

-- 
Kees Cook