netdev - Re: [PATCH net] net/sched: act_simple: don't leak 'index' in the error path

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Message-ID: <CAM_iQpUg5sDfXk1i1aJh_28cV7VpR2PpggnoR3jOJNxqDJiNSw@mail.gmail.com>
Date:   Wed, 14 Mar 2018 11:41:08 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Davide Caratti <dcaratti@...hat.com>
Cc:     Jamal Hadi Salim <jhs@...atatu.com>, Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH net] net/sched: act_simple: don't leak 'index' in the
 error path

On Tue, Mar 13, 2018 at 7:13 PM, Davide Caratti <dcaratti@...hat.com> wrote:
> Similarly to what other TC actions do, we can duplicate 'sdata' before
> calling tcf_idr_create(), and avoid calling tcf_idr_cleanup(), so that
> leaks of 'index' don't occur anymore.

Looks like we just need to replace the tcf_idr_cleanup() with
tcf_idr_release()? Which is also simpler.


>
> Signed-off-by: Davide Caratti <dcaratti@...hat.com>
> ---
>
> Notes:
>     Hello,
>
>     I observed this faulty behavior on act_bpf, in case of negative return
>     value of tcf_bpf_init_from_ops() and tcf_bpf_init_from_efd(). Then I
>     tried on act_simple, that parses its parameter in a similar way, and
>     reproduced the same leakage of 'index'.
>
>     So, unless you think we should fix this issue in a different way (i.e.
>     changing tcf_idr_cleanup() ), I will post a similar fix for act_bpf.
>
>     Any feedback is welcome, thank you in advance!

Looks like all other callers of tcf_idr_cleanup() need to be replaced too,
but I don't audit all of them...


[...]

>         if (!exists) {
> +               defdata = nla_strdup(tb[TCA_DEF_DATA], GFP_KERNEL);
> +               if (unlikely(!defdata))
> +                       return -ENOMEM;
> +
>                 ret = tcf_idr_create(tn, parm->index, est, a,
>                                      &act_simp_ops, bind, false);
>                 if (ret)
>                         return ret;

You leak memory here on failure, BTW.