netdev - Re: [PATCH net-next 1/3] net: gso: do not include jumbogram HBH header in seglen calculation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ef8ed31a-7b3b-439a-a3e1-8de298827bbd@gmail.com>
Date: Tue, 2 Dec 2025 17:55:55 +0100
From: Mariusz Klimek <maklimek97@...il.com>
To: Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/3] net: gso: do not include jumbogram HBH
 header in seglen calculation

On 12/2/25 13:06, Paolo Abeni wrote:
> On 12/2/25 12:36 PM, Paolo Abeni wrote:
>> On 11/27/25 10:13 AM, Mariusz Klimek wrote:
>>> This patch fixes an issue in skb_gso_network_seglen where the calculated
>>> segment length includes the HBH headers of BIG TCP jumbograms despite these
>>> headers being removed before segmentation. These headers are added by GRO
>>> or by ip6_xmit for BIG TCP packets and are later removed by GSO. This bug
>>> causes MTU validation of BIG TCP jumbograms to fail.
>>>
>>> Signed-off-by: Mariusz Klimek <maklimek97@...il.com>
>>> ---
>>>  net/core/gso.c | 4 ++++
>>>  1 file changed, 4 insertions(+)
>>>
>>> diff --git a/net/core/gso.c b/net/core/gso.c
>>> index bcd156372f4d..251a49181031 100644
>>> --- a/net/core/gso.c
>>> +++ b/net/core/gso.c
>>> @@ -180,6 +180,10 @@ static unsigned int skb_gso_network_seglen(const struct sk_buff *skb)
>>>  	unsigned int hdr_len = skb_transport_header(skb) -
>>>  			       skb_network_header(skb);
>>>  
>>> +	/* Jumbogram HBH header is removed upon segmentation. */
>>> +	if (skb->protocol == htons(ETH_P_IPV6) && skb->len > IPV6_MAXPLEN)
>>> +		hdr_len -= sizeof(struct hop_jumbo_hdr);
>>
>> Isn't the above condition a bit too course-grain? Specifically, can
>> UDP-encapsulated GSO packets wrongly hit it?
> 
> I forgot to mention that AI review noted the above check should be
> placed in skb_gso_mac_seglen(), too:
> 
> https://netdev-ai.bots.linux.dev/ai-review.html?id=bed04a62-0239-4392-a9a3-2399fee27630
> 
> AFAICS, it the OVS forwarding path should be impacted.
> 
> /P
> 

Right. I'll add a helper function.

-- 
Mariusz K.