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Date:   Thu, 10 Mar 2022 14:42:29 -0800
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To:     Jakub Kicinski <kuba@kernel.org>
Cc:     davem@davemloft.net,
        Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
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From:   Tadeusz Struk <tadeusz.struk@linaro.org>
Subject: Re: [PATCH v2] net: ipv6: fix skb_over_panic in __ip6_append_data
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On 3/10/22 14:30, Jakub Kicinski wrote:
>> +
>> +			/*
>> +			 *	Check if there is still room for payload
>> +			 */
> TBH I think the check is self-explanatory. Not worth a banner comment,
> for sure.

Ok

> 
>> +			if (fragheaderlen >= mtu) {
>> +				err = -EMSGSIZE;
>> +				kfree_skb(skb);
>> +				goto error;
>> +			}
> Not sure if Willem prefers this placement, but seems like we can lift
> this check out of the loop, as soon as fragheaderlen and mtu are known.
> 

He said to check it before the skb_put() and so I did.
The fragheaderlen is known early, but mtu can be updated inside the loop
by ip6_append_data_mtu() so I'm not sure we can do the check before that.

-- 
Thanks,
Tadeusz