netdev - Re: [PATCH net-next] neigh: add netlink filtering based on LLADDR for dump

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Message-ID: <92170809-c45e-4b39-09b7-37b28b05d479@wifirst.fr>
Date:   Thu, 8 Oct 2020 16:49:52 +0200
From:   Florent Fourcot <florent.fourcot@...irst.fr>
To:     Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] neigh: add netlink filtering based on LLADDR for
 dump

Hello Éric,

>> +	if (memcmp(lladdr, neigh->ha, neigh->dev->addr_len) != 0)
> 
> Where do you check that lladdr contains exactly neigh->dev->addr_len bytes ?

True, I do not check. I had some doubt about the best implementation, 
since we could do:
  * exact matching
  * prefix matching (with a memcmp on length of lladdr)

Do you may have an opinion on the best choice?

>> +		case NDA_LLADDR:
>> +			filter->lladdr = nla_data(tb[i]);
> 
> This comes from user space, and could contains an arbitrary amount of bytes, like 0 byte.
> 
> You probably have to store the full attribute, so that you can use nla_len() and nla_data()
> 

I will send a v2.

By the way, it looks like neigh_add() function never check if NDA_LLADDR 
length is greater than dev->addr_len (it only rejects smaller values). 
Should we add a check on it? I do not see any impact today, except than 
user does not receive an error on invalid data, it will configure an 
entry anyway.

Thanks,

-- 
Florent.