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SubjectRe: [RFC] netfilter: cttimeout: remove VLA in ctnl_timeout_parse_policy
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On 03/11/2018 05:21 PM, Pablo Neira Ayuso wrote:
> On Sun, Mar 11, 2018 at 05:12:09PM -0500, Gustavo A. R. Silva wrote:
>> Hi Pablo,
>>
>> On 03/11/2018 05:04 PM, Pablo Neira Ayuso wrote:
>>> On Tue, Mar 06, 2018 at 12:47:55PM -0600, Gustavo A. R. Silva wrote:
>>>> In preparation to enabling -Wvla, remove VLA and replace it
>>>> with dynamic memory allocation.
>>>
>>> Looks good but...
>>>
>>>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
>>>> ---
>>>> net/netfilter/nfnetlink_cttimeout.c | 12 ++++++++++--
>>>> 1 file changed, 10 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/net/netfilter/nfnetlink_cttimeout.c b/net/netfilter/nfnetlink_cttimeout.c
>>>> index 95b0470..a2f7d92 100644
>>>> --- a/net/netfilter/nfnetlink_cttimeout.c
>>>> +++ b/net/netfilter/nfnetlink_cttimeout.c
>>>> @@ -52,18 +52,26 @@ ctnl_timeout_parse_policy(void *timeouts,
>>>> struct net *net, const struct nlattr *attr)
>>>> {
>>>> int ret = 0;
>>>> + struct nlattr **tb = NULL;
>>>
>>> I think we don't need to initialize this, right?
>>>
>>
>> We actually do have to initialized it because in the unlikely case that the
>> code block inside the 'if' below is not executed, then we will end up
>> freeing an uninitialized pointer.
>
> I see, you're right indeed.
>
> We can probably simplify this code, but just doing:
>
> if (!l4proto->ctnl_timeout.nlattr_to_obj))
> return 0;
>

I wonder if it is better to code this instead:

if (unlikely(!l4proto->ctnl_timeout.nlattr_to_obj)))
return 0;


> netlink attribute parsing here.
>
> You could even remove the likely() thing, which doesn't make much
> sense for control plane code.
>

Why is that?

> I understand this is a larger change, but I think this function will
> look better while we're removing VLA.
>
> Would you mind having a look? I'd appreciate if so.
>

I can do that. No problem.

Thanks
--
Gustavo

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