linux-kernel - Re: [PATCH v2 1/1] selinux: fix double free

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Message-ID: <CAHC9VhTd0HSv6Yk8NxJeC=U7wPb0AtRturAGYLfxg8B13h0FOA@mail.gmail.com>
Date:   Wed, 10 Jun 2020 22:13:15 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     trix@...hat.com
Cc:     Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        Ondrej Mosnacek <omosnace@...hat.com>, jeffv@...gle.com,
        rgb@...hat.com, selinux@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] selinux: fix double free

On Wed, Jun 10, 2020 at 5:57 PM <trix@...hat.com> wrote:
> From: Tom Rix <trix@...hat.com>
>
> Clang's static analysis tool reports these double free memory errors.
>
> security/selinux/ss/services.c:2987:4: warning: Attempt to free released memory [unix.Malloc]
>                         kfree(bnames[i]);
>                         ^~~~~~~~~~~~~~~~
> security/selinux/ss/services.c:2990:2: warning: Attempt to free released memory [unix.Malloc]
>         kfree(bvalues);
>         ^~~~~~~~~~~~~~
>
> So improve the security_get_bools error handling by freeing these variables
> and setting their return pointers to NULL and the return len to 0
>
> Signed-off-by: Tom Rix <trix@...hat.com>
> ---
>  security/selinux/ss/services.c | 4 ++++
>  1 file changed, 4 insertions(+)

Thanks Tom for the patch and Stephen for the review.

I've marked this for stable and merged it into selinux/stable-5.8.
Considering we are just a few days away from the close of the merge
window and -rc1, I'll probably hold off until next to send this up to
Linus.

> diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
> index 313919bd42f8..ef0afd878bfc 100644
> --- a/security/selinux/ss/services.c
> +++ b/security/selinux/ss/services.c
> @@ -2888,8 +2888,12 @@ int security_get_bools(struct selinux_state *state,
>         if (*names) {
>                 for (i = 0; i < *len; i++)
>                         kfree((*names)[i]);
> +               kfree(*names);
>         }
>         kfree(*values);
> +       *len = 0;
> +       *names = NULL;
> +       *values = NULL;
>         goto out;
>  }
>
> --
> 2.18.1

-- 
paul moore
www.paul-moore.com