linux-kernel - Re: [PATCH net 1/1] tcp: check skb is non-NULL in tcp_rto_delta

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Message-ID: <2d4bc830-0759-41c1-ad83-10413150152f@akamai.com>
Date: Fri, 6 Sep 2024 16:16:57 -0700
From: Josh Hunt <johunt@...mai.com>
To: Eric Dumazet <edumazet@...gle.com>, Neal Cardwell <ncardwell@...gle.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 1/1] tcp: check skb is non-NULL in tcp_rto_delta_us()

On 8/22/24 11:55 PM, Eric Dumazet wrote:
> On Fri, Aug 23, 2024 at 5:34 AM Josh Hunt <johunt@...mai.com> wrote:
>>
>> There have been multiple occassions where we have crashed in this path
>> because packets_out suggested there were packets on the write or retransmit
>> queues, but in fact there weren't leading to a NULL skb being dereferenced.
>> While we should fix that root cause we should also just make sure the skb
>> is not NULL before dereferencing it. Also add a warn once here to capture
>> some information if/when the problem case is hit again.
>>
>> Signed-off-by: Josh Hunt <johunt@...mai.com>
> 
> Hi Josh
> 
> We do not want a patch series of one patch, with the stack trace in
> the cover letter.
> Please send a standalone patch, with all the information in its changelog.
> 
> 1) Add Neal Cardwell in the CC list.

Sending v2 now with Neal included.

> 
> 2) Are you using TCP_REPAIR by any chance ?
> 

No, we're not using TCP_REPAIR on these machines.

> 3) Please double check your kernel has these fixes.
> 
> commit 1f85e6267caca44b30c54711652b0726fadbb131    tcp: do not send
> empty skb from tcp_write_xmit()
> commit 0c175da7b0378445f5ef53904247cfbfb87e0b78     tcp: prohibit
> TCP_REPAIR_OPTIONS if data was already sent
> 

We have the first commit, but not the second.

Josh