linux-kernel - Re: [PATCH 1/3] selinux: consistently clear cond

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Date:   Tue, 1 Feb 2022 12:38:47 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     vbendel@...hat.com
Cc:     stephen.smalley.work@...il.com, eparis@...isplace.org,
        omosnace@...hat.com, selinux@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] selinux: consistently clear cond_list on error paths

On Fri, Jan 28, 2022 at 3:29 PM <vbendel@...hat.com> wrote:
> From: Vratislav Bendel <vbendel@...hat.com>
>
> Currently there are two users of policydb->cond_list: cond_read_list()
> and duplicate_policydb_cond_list(). On their error path one clears
> ->cond_list to NULL, but the other doesn't.
> Make the behavior consistent by resetting ->cond_list to NULL in
> cond_list_destroy(), which is called by both on the error path.

It's also important to see if there are any callers of
cond_list_destroy() which incorrectly might be making use of
policydb::cond_list after it has been freed; thankfully that does not
appear to be the case in any of the call paths I looked at just now.
As this is more a a style/Right-Thing-To-Do patch and not an immediate
bugfix I'm going to go and merge this into selinux/next.

Thanks Vratislav.

> Signed-off-by: Vratislav Bendel <vbendel@...hat.com>
> ---
>  security/selinux/ss/conditional.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
> index 2ec6e5cd25d9..1d0e5f326b62 100644
> --- a/security/selinux/ss/conditional.c
> +++ b/security/selinux/ss/conditional.c
> @@ -152,6 +152,7 @@ static void cond_list_destroy(struct policydb *p)
>         for (i = 0; i < p->cond_list_len; i++)
>                 cond_node_destroy(&p->cond_list[i]);
>         kfree(p->cond_list);
> +       p->cond_list = NULL;
>  }
>
>  void cond_policydb_destroy(struct policydb *p)
> @@ -441,7 +442,6 @@ int cond_read_list(struct policydb *p, void *fp)
>         return 0;
>  err:
>         cond_list_destroy(p);
> -       p->cond_list = NULL;
>         return rc;
>  }
>
> --
> 2.26.3

-- 
paul-moore.com