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

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Date:   Thu, 15 Mar 2018 17:43:36 -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 Wed, Mar 14, 2018 at 3:43 PM, Davide Caratti <dcaratti@...hat.com> wrote:
> hello Cong, thank you for reviewing this.
>
> On Wed, 2018-03-14 at 11:41 -0700, Cong Wang wrote:
>> On Tue, Mar 13, 2018 at 7:13 PM, Davide Caratti <dcaratti@...hat.com> wrote:
>>
>> Looks like we just need to replace the tcf_idr_cleanup() with
>> tcf_idr_release()? Which is also simpler.
>
> I just tried it on act_simple, and I can confirm: 'index' does not leak
> anymore if alloc_defdata() fails to kzalloc(), and then tcf_idr_release()
> is called in place of of tcf_idr_cleanup().

Good.

>
>> Looks like all other callers of tcf_idr_cleanup() need to be replaced too,
>> but I don't audit all of them...
>
> no problem, I can try to do that, it's not going to be a big series
> anyway.


Please audit all of them.


>
> while at it, I will also fix other spots where the same bug can be
> reproduced, even if tcf_idr_cleanup() is not there: for example, when
> tcf_vlan_init() fails allocating struct tcf_vlan_params *p,
>
> ASSERT_RTNL();
> p = kzalloc(sizeof(*p), GFP_KERNEL);
> if (!p) {
>         if (ovr)
>                 tcf_idr_release(*a, bind);
>         return -ENOMEM;
> }
>
> the followinng behavior can be observed:
>
> # tc actions flush action vlan
> # tc actions add action vlan pop index 5
> RTNETLINK answers: Cannot allocate memory
> We have an error talking to the kernel
> # tc actions add action vlan pop index 5
> RTNETLINK answers: No space left on device
> We have an error talking to the kernel
> # tc actions add action vlan pop index 5
> RTNETLINK answers: No space left on device
> We have an error talking to the kernel
>
> Probably testing the value of 'ovr' here is wrong, or maybe it's
> not enough: I will also verify what happens using 'replace'
> keyword instead of 'add'.

Please fix it separately if really needed, and it would be nicer
if you can add your test cases to tools/testing/selftests/tc-testing/.

Thanks!