netdev - Re: [Bug report] NFS patch breaks TLS device-offloaded TX zerocopy

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Message-ID: <8683155c-79ad-4090-9aff-fc8d765b096b@gmail.com>
Date: Tue, 6 Aug 2024 13:07:47 +0300
From: Tariq Toukan <ttoukan.linux@...il.com>
To: Sagi Grimberg <sagi@...mberg.me>, Christoph Hellwig <hch@....de>,
 Anna Schumaker <Anna.Schumaker@...app.com>,
 Trond Myklebust <trondmy@...nel.org>, linux-nfs@...r.kernel.org,
 Boris Pismenny <borisp@...dia.com>, John Fastabend
 <john.fastabend@...il.com>, Jakub Kicinski <kuba@...nel.org>,
 Maxim Mikityanskiy <maxtram95@...il.com>
Cc: Saeed Mahameed <saeedm@...dia.com>, Gal Pressman <gal@...dia.com>,
 Networking <netdev@...r.kernel.org>, Paolo Abeni <pabeni@...hat.com>,
 Eric Dumazet <edumazet@...gle.com>, "David S. Miller" <davem@...emloft.net>,
 Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
 Leon Romanovsky <leon@...nel.org>, Tariq Toukan <tariqt@...dia.com>
Subject: Re: [Bug report] NFS patch breaks TLS device-offloaded TX zerocopy

On 06/08/2024 11:09, Sagi Grimberg wrote:
> 
> 
> 
> On 06/08/2024 7:43, Tariq Toukan wrote:
>>
>>
>> On 05/08/2024 14:43, Sagi Grimberg wrote:
>>>
>>>
>>>
>>> On 05/08/2024 13:40, Tariq Toukan wrote:
>>>> Hi,
>>>>
>>>> A recent patch [1] to 'fs' broke the TX TLS device-offloaded flow 
>>>> starting from v6.11-rc1.
>>>>
>>>> The kernel crashes. Different runs result in different kernel traces.
>>>> See below [2].
>>>> All of them disappear once patch [1] is reverted.
>>>>
>>>> The issues appears only with "sendfile on and zerocopy on".
>>>> We couldn't repro with "sendfile off", or with "sendfile on and 
>>>> zerocopy off".
>>>>
>>>> The repro test is as simple as a repeated client/server 
>>>> communication (wrk/nginx), with sendfile on and zc on, and with 
>>>> "tls-hw-tx-offload: on".
>>>>
>>>> $ for i in `seq 10`; do wrk -b::2:2:2:3 -t10 -c100 -d15 --timeout 5s 
>>>> https://[::2:2:2:2]:20448/16000b.img; done
>>>>
>>>> We can provide more details if needed, to help with the analysis and 
>>>> debug.
>>>
>>> Does tls sw (i.e. no offload) also break?
>>>
>>
>> No it doesn't.
>> Only the "sendfile with ZC" flow of the TX device-offloaded TLS.
> 

Adding Maxim Mikityanskiy, he might have some insights.

> Not familiar with the TLS offload code, are there any assumptions on 
> PAGE_SIZE contig buffers? Or assumptions on individual
> page references/lifetime?
> 
> The sporadic panics you reported look like a result of memory corruption 
> or use-after-free conditions.